63 results on '"McDougall SJ"'
Search Results
2. Feeding signals inhibit fluid-satiation signals in the mouse lateral parabrachial nucleus to increase intake of highly palatable, caloric solutions
- Author
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Aitken, CM, Jaramillo, JCM, Davis, W, Brennan-Xie, L, Mcdougall, SJ, Lawrence, AJ, Ryan, PJ, Aitken, CM, Jaramillo, JCM, Davis, W, Brennan-Xie, L, Mcdougall, SJ, Lawrence, AJ, and Ryan, PJ
- Abstract
Chemogenetic activation of oxytocin receptor-expressing neurons in the parabrachial nucleus (OxtrPBN neurons) acts as a satiation signal for water. In this research, we investigated the effect of activating OxtrPBN neurons on satiation for different types of fluids. Chemogenetic activation of OxtrPBN neurons in male and female transgenic OxtrCre mice robustly suppressed the rapid, initial (15-min) intake of several solutions after dehydration: water, sucrose, ethanol and saccharin, but only slightly decreased intake of Ensure®, a highly caloric solution (1 kcal/mL; containing 3.72 g protein, 3.27 g fat, 13.42 g carbohydrates, and 1.01 g dietary fibre per 100 mL). OxtrPBN neuron activation also suppressed cumulative, longer-term (2-h) intake of lower caloric, less palatable solutions, but not highly caloric, palatable solutions. These results suggest that OxtrPBN neurons predominantly control initial fluid-satiation responses after rehydration, but not longer-term intake of highly caloric, palatable solutions. The suppression of fluid intake was not because of anxiogenesis, but because OxtrPBN neuron activation decreased anxiety-like behaviour. To investigate the role of different PBN subdivisions on the intake of different solutions, we examined FOS as a proxy marker of PBN neuron activation. Different PBN subdivisions were activated by different solutions: the dorsolateral PBN similarly by all fluids; the external lateral PBN by caloric but not non-caloric solutions; and the central lateral PBN primarily by highly palatable solutions, suggesting PBN subdivisions regulate different aspects of fluid intake. To explore the possible mechanisms underlying the minimal suppression of Ensure® after OxtrPBN neuron activation, we demonstrated in in vitro slice recordings that the feeding-associated agouti-related peptide (AgRP) inhibited OxtrPBN neuron firing in a concentration-related manner, suggesting possible inhibition by feeding-related neurocircuitry of fluid satiatio
- Published
- 2023
3. Selective transduction and photoinhibition of pre-Bötzinger complex neurons that project to the facial nucleus in rats affects nasofacial activity
- Author
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Melo, MR, Wykes, AD, Connelly, AA, Bassi, JK, Cheung, SD, McDougall, SJ, Menuet, C, Bathgate, RAD, Allen, AM, Melo, MR, Wykes, AD, Connelly, AA, Bassi, JK, Cheung, SD, McDougall, SJ, Menuet, C, Bathgate, RAD, and Allen, AM
- Abstract
The pre-Bötzinger complex (preBötC), a key primary generator of the inspiratory breathing rhythm, contains neurons that project directly to facial nucleus (7n) motoneurons to coordinate orofacial and nasofacial activity. To further understand the identity of 7n-projecting preBötC neurons, we used a combination of optogenetic viral transgenic approaches to demonstrate that selective photoinhibition of these neurons affects mystacial pad activity, with minimal effects on breathing. These effects are altered by the type of anesthetic employed and also between anesthetized and conscious states. The population of 7n-projecting preBötC neurons we transduced consisted of both excitatory and inhibitory neurons that also send collaterals to multiple brainstem nuclei involved with the regulation of autonomic activity. We show that modulation of subgroups of preBötC neurons, based on their axonal projections, is a useful strategy to improve our understanding of the mechanisms that coordinate and integrate breathing with different motor and physiological behaviors. This is of fundamental importance, given that abnormal respiratory modulation of autonomic activity and orofacial behaviors have been associated with the development and progression of diseases.
- Published
- 2023
4. Analysis of the distribution of vagal afferent projections from different peripheral organs to the nucleus of the solitary tract in rats
- Author
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Bassi, JK, Connelly, AA, Butler, AG, Liu, Y, Ghanbari, A, Farmer, DGS, Jenkins, MW, Melo, MR, McDougall, SJ, Allen, AM, Bassi, JK, Connelly, AA, Butler, AG, Liu, Y, Ghanbari, A, Farmer, DGS, Jenkins, MW, Melo, MR, McDougall, SJ, and Allen, AM
- Abstract
Anatomical tracing studies examining the vagal system can conflate details of sensory afferent and motor efferent neurons. Here, we used a serotype of adeno-associated virus that transports retrogradely and exhibits selective tropism for vagal afferents, to map their soma location and central termination sites within the nucleus of the solitary tract (NTS). We examined the vagal sensory afferents innervating the trachea, duodenum, stomach, or heart, and in some animals, from two organs concurrently. We observed no obvious somatotopy in the somata distribution within the nodose ganglion. The central termination patterns of afferents from different organs within the NTS overlap substantially. Convergence of vagal afferent inputs from different organs onto single NTS neurons is observed. Abdominal and thoracic afferents terminate throughout the NTS, including in the rostral NTS, where the 7th cranial nerve inputs are known to synapse. To address whether the axonal labeling produced by viral transduction is so widespread because it fills axons traveling to their targets, and not just terminal fields, we labeled pre and postsynaptic elements of vagal afferents in the NTS . Vagal afferents form multiple putative synapses as they course through the NTS, with each vagal afferent neuron distributing sensory signals to multiple second-order NTS neurons. We observe little selectivity between vagal afferents from different visceral targets and NTS neurons with common neurochemical phenotypes, with afferents from different organs making close appositions with the same NTS neuron. We conclude that specific viscerosensory information is distributed widely within the NTS and that the coding of this input is probably determined by the intrinsic properties and projections of the second-order neuron.
- Published
- 2022
5. Selective optogenetic stimulation of efferent fi bers in the vagus nerve of a large mammal
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Booth, LC, Yao, ST, Korsak, A, Farmer, DGS, Hood, SG, McCormick, D, Boesley, Q, Connelly, AA, McDougall, SJ, Korim, WS, Guild, S-J, Mastitskaya, S, Le, P, Teschemacher, AG, Kasparov, S, Ackland, GL, Malpas, SC, McAllen, RM, Allen, AM, May, CN, Gourine, AV, Booth, LC, Yao, ST, Korsak, A, Farmer, DGS, Hood, SG, McCormick, D, Boesley, Q, Connelly, AA, McDougall, SJ, Korim, WS, Guild, S-J, Mastitskaya, S, Le, P, Teschemacher, AG, Kasparov, S, Ackland, GL, Malpas, SC, McAllen, RM, Allen, AM, May, CN, and Gourine, AV
- Abstract
BACKGROUND: Electrical stimulation applied to individual organs, peripheral nerves, or specific brain regions has been used to treat a range of medical conditions. In cardiovascular disease, autonomic dysfunction contributes to the disease progression and electrical stimulation of the vagus nerve has been pursued as a treatment for the purpose of restoring the autonomic balance. However, this approach lacks selectivity in activating function- and organ-specific vagal fibers and, despite promising results of many preclinical studies, has so far failed to translate into a clinical treatment of cardiovascular disease. OBJECTIVE: Here we report a successful application of optogenetics for selective stimulation of vagal efferent activity in a large animal model (sheep). METHODS AND RESULTS: Twelve weeks after viral transduction of a subset of vagal motoneurons, strong axonal membrane expression of the excitatory light-sensitive ion channel ChIEF was achieved in the efferent projections innervating thoracic organs and reaching beyond the level of the diaphragm. Blue laser or LED light (>10 mW mm-2; 1 ms pulses) applied to the cervical vagus triggered precisely timed, strong bursts of efferent activity with evoked action potentials propagating at speeds of ∼6 m s-1. CONCLUSIONS: These findings demonstrate that in species with a large, multi-fascicled vagus nerve, it is possible to stimulate a specific sub-population of efferent fibers using light at a site remote from the vector delivery, marking an important step towards eventual clinical use of optogenetic technology for autonomic neuromodulation.
- Published
- 2021
6. Use of a physiological reflex to standardize vagal nerve stimulation intensity improves data reproducibility in a memory extinction assay
- Author
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Butler, AG, O'Callaghan, EL, Allen, AM, McDougall, SJ, Butler, AG, O'Callaghan, EL, Allen, AM, and McDougall, SJ
- Abstract
BACKGROUND: Modulating brainstem activity, via electrical vagus nerve stimulation (VNS), influences cognitive functions, including memory. However, controlling for changes in stimulus efficacy during chronic studies, and response variability between subjects, is problematic. OBJECTIVE/HYPOTHESIS: We hypothesized that recruitment of an autonomic reflex, the Hering-Breuer reflex, would provide robust confirmation of VNS efficacy. We compared this to measurement of electrode resistance over time. We also examined whether VNS modulates contextual memory extinction. METHODS: Electrodes for VNS and diaphragm electromyography recording were implanted into anesthetized Sprague Dawley rats. When conscious, we measured the electrode resistance as well as the minimum VNS current required to evoke the Hering-Breuer reflex, before, and after, an inhibitory avoidance assay - a two chamber, dark/light model, where the dark compartment was paired with an aversive foot shock. The extinction of this contextual memory was assessed in sham and VNS treated rats, with VNS administered for 30 s at 1.5 times the Hering-Breuer reflex threshold during extinction memory formation. RESULTS: Assessment of VNS-evoked Hering-Breuer reflex successfully identified defective electrodes. VNS accelerated extinction memory and decreased multiple physiological metrics of fear expression. We observed an inverse relationship between memory extinction and respiratory rate during the behavioural assay. Additionally, no current - response relationship between VNS and extinction memory formation was established. CONCLUSION: These data demonstrate that reliable, experimental VNS studies can be produced by verifying reflex initiation as a consequence of stimulation. Further, studies could be standardised by indexing stimulator efficacy to initiation of autonomic reflexes.
- Published
- 2021
7. FGF-MAPK signaling regulates human deep-layer corticogenesis
- Author
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Gantner, CW, Hunt, CPJ, Niclis, JC, Penna, V, McDougall, SJ, Thompson, LH, Parish, CL, Gantner, CW, Hunt, CPJ, Niclis, JC, Penna, V, McDougall, SJ, Thompson, LH, and Parish, CL
- Abstract
Despite heterogeneity across the six layers of the mammalian cortex, all excitatory neurons are generated from a single founder population of neuroepithelial stem cells. However, how these progenitors alter their layer competence over time remains unknown. Here, we used human embryonic stem cell-derived cortical progenitors to examine the role of fibroblast growth factor (FGF) and Notch signaling in influencing cell fate, assessing their impact on progenitor phenotype, cell-cycle kinetics, and layer specificity. Forced early cell-cycle exit, via Notch inhibition, caused rapid, near-exclusive generation of deep-layer VI neurons. In contrast, prolonged FGF2 promoted proliferation and maintained progenitor identity, delaying laminar progression via MAPK-dependent mechanisms. Inhibiting MAPK extended cell-cycle length and led to generation of layer-V CTIP2+ neurons by repressing alternative laminar fates. Taken together, FGF/MAPK regulates the proliferative/neurogenic balance in deep-layer corticogenesis and provides a resource for generating layer-specific neurons for studying development and disease.
- Published
- 2021
8. Prebötzinger complex neurons drive respiratory modulation of blood pressure and heart rate
- Author
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Menuet, C, Connelly, AA, Bassi, JK, Melo, MR, Le, S, Kamar, J, Kumar, NN, McDougall, SJ, McMullan, S, Allen, AM, Menuet, C, Connelly, AA, Bassi, JK, Melo, MR, Le, S, Kamar, J, Kumar, NN, McDougall, SJ, McMullan, S, and Allen, AM
- Abstract
Heart rate and blood pressure oscillate in phase with respiratory activity. A component of these oscillations is generated centrally, with respiratory neurons entraining the activity of pre-sympathetic and parasympathetic cardiovascular neurons. Using a combination of optogenetic inhibition and excitation in vivo and in situ in rats, as well as neuronal tracing, we demonstrate that preBötzinger Complex (preBötC) neurons, which form the kernel for inspiratory rhythm generation, directly modulate cardiovascular activity. Specifically, inhibitory preBötC neurons modulate cardiac parasympathetic neuron activity whilst excitatory preBötC neurons modulate sympathetic vasomotor neuron activity, generating heart rate and blood pressure oscillations in phase with respiration. Our data reveal yet more functions entrained to the activity of the preBötC, with a role in generating cardiorespiratory oscillations. The findings have implications for cardiovascular pathologies, such as hypertension and heart failure, where respiratory entrainment of heart rate is diminished and respiratory entrainment of blood pressure exaggerated.
- Published
- 2020
9. A Chemogenetic Tool that Enables Functional Neural Circuit Analysis
- Author
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Ngo, HB, Melo, MR, Layfield, S, Connelly, AA, Bassi, JK, Xie, L, Menuet, C, McDougall, SJ, Bathgate, RAD, Allen, AM, Ngo, HB, Melo, MR, Layfield, S, Connelly, AA, Bassi, JK, Xie, L, Menuet, C, McDougall, SJ, Bathgate, RAD, and Allen, AM
- Abstract
Chemogenetics enables manipulation of neuronal activity in experimental animals. While providing information about the transduced neuron expressing a ligand-activated molecule, chemogenetics does not provide understanding about the antecedent circuit that drives that neuron's activity. For current approaches, this is not feasible, because the activating molecules are not genetically encoded. The insect allatostatin/allatostatin receptor system, a highly specific, powerful inhibitory chemogenetic approach, has this advantage, because the ligand, being a peptide, is genetically encoded. We developed viral vector-based systems to express biologically active allatostatin in neurons in vivo and allatostatin receptors in subpopulations of postsynaptic neurons. We demonstrate that activity-dependent release of allatostatin induces inhibition of allatostatin receptor-expressing neurons. We validate the approach in the vagal viscerosensory system where inhibitory, rather than the usual excitatory, viscerosensory input leads to sustained decreases in baroreceptor reflex sensitivity and bodyweight.
- Published
- 2020
10. Pharmacogenetic stimulation of neuronal activity increases myelination in an axon-specific manner
- Author
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Mitew, S, Gobius, I, Fenlon, LR, McDougall, SJ, Hawkes, D, Xing, YL, Bujalka, H, Gundlach, AL, Richards, LJ, Kilpatrick, TJ, Merson, TD, Emery, B, Mitew, S, Gobius, I, Fenlon, LR, McDougall, SJ, Hawkes, D, Xing, YL, Bujalka, H, Gundlach, AL, Richards, LJ, Kilpatrick, TJ, Merson, TD, and Emery, B
- Abstract
Mounting evidence suggests that neuronal activity influences myelination, potentially allowing for experience-driven modulation of neural circuitry. The degree to which neuronal activity is capable of regulating myelination at the individual axon level is unclear. Here we demonstrate that stimulation of somatosensory axons in the mouse brain increases proliferation and differentiation of oligodendrocyte progenitor cells (OPCs) within the underlying white matter. Stimulated axons display an increased probability of being myelinated compared to neighboring non-stimulated axons, in addition to being ensheathed with thicker myelin. Conversely, attenuating neuronal firing reduces axonal myelination in a selective activity-dependent manner. Our findings reveal that the process of selecting axons for myelination is strongly influenced by the relative activity of individual axons within a population. These observed cellular changes are consistent with the emerging concept that adaptive myelination is a key mechanism for the fine-tuning of neuronal circuitry in the mammalian CNS.
- Published
- 2018
11. Efficiently Specified Ventral Midbrain Dopamine Neurons from Human Pluripotent Stem Cells Under Xeno-Free Conditions Restore Motor Deficits in Parkinsonian Rodents
- Author
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Niclis, JC, Gantner, CW, Alsanie, WF, McDougall, SJ, Bye, CR, Elefanty, AG, Stanley, EG, Haynes, JM, Pouton, CW, Thompson, LH, Parish, CL, Niclis, JC, Gantner, CW, Alsanie, WF, McDougall, SJ, Bye, CR, Elefanty, AG, Stanley, EG, Haynes, JM, Pouton, CW, Thompson, LH, and Parish, CL
- Abstract
Recent studies have shown evidence for the functional integration of human pluripotent stem cell (hPSC)-derived ventral midbrain dopamine (vmDA) neurons in animal models of Parkinson's disease. Although these cells present a sustainable alternative to fetal mesencephalic grafts, a number of hurdles require attention prior to clinical translation. These include the persistent use of xenogeneic reagents and challenges associated with scalability and storage of differentiated cells. In this study, we describe the first fully defined feeder- and xenogeneic-free protocol for the generation of vmDA neurons from hPSCs and utilize two novel reporter knock-in lines (LMX1A-eGFP and PITX3-eGFP) for in-depth in vitro and in vivo tracking. Across multiple embryonic and induced hPSC lines, this "next generation" protocol consistently increases both the yield and proportion of vmDA neural progenitors (OTX2/FOXA2/LMX1A) and neurons (FOXA2/TH/PITX3) that display classical vmDA metabolic and electrophysiological properties. We identify the mechanism underlying these improvements and demonstrate clinical applicability with the first report of scalability and cryopreservation of bona fide vmDA progenitors at a time amenable to transplantation. Finally, transplantation of xeno-free vmDA progenitors from LMX1A- and PITX3-eGFP reporter lines into Parkinsonian rodents demonstrates improved engraftment outcomes and restoration of motor deficits. These findings provide important and necessary advancements for the translation of hPSC-derived neurons into the clinic. SIGNIFICANCE: The authors report the generation of highly pure midbrain dopamine cultures under feeder-free, fully defined, and xeno-free conditions from human pluripotent stem cells. Xeno-free differentiated cells display gene, protein, and electrophysiological properties of midbrain neurons, as well as improved grafting outcomes in Parkinsonian rodents, observations enhanced by the use of two novel reporter lines of interest t
- Published
- 2017
12. Dedicated C-fibre viscerosensory pathways to central nucleus of the amygdala
- Author
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McDougall, SJ, Guo, H, Andresen, MC, McDougall, SJ, Guo, H, and Andresen, MC
- Abstract
KEY POINTS: Emotions are accompanied by concordant changes in visceral function, including cardiac output, respiration and digestion. One major forebrain integrator of emotional responses, the amygdala, is considered to rely on embedded visceral afferent information, although few details are known. In the present study, we retrogradely transported dye from the central nucleus of the amygdala (CeA) to identify CeA-projecting nucleus of the solitary tract (NTS) neurons for synaptic characterization and compared them with unlabelled, near-neighboor NTS neurons. Solitary tract (ST) afferents converged onto NTS-CeA second-order sensory neurons in greater numbers, as well as indirectly via polysynaptic pathways. Unexpectedly, all mono- and polysynaptic ST afferent pathways to NTS-CeA neurons were organized exclusively as either transient receptor potential cation channel subfamily V member 1 (TRPV1)-sensitive or TRPV1-resistant, regardless of whether intervening neurons were excitatory or inhibitory. This strict sorting provides viscerosensory signals to CeA about visceral conditions with respect to being either 'normal' via A-fibres or 'alarm' via TRPV1 expressing C-fibres and, accordingly, this pathway organization probably encodes interoceptive status. ABSTRACT: Emotional state is impacted by changes in visceral function, including blood pressure, breathing and digestion. A main line of viscerosensory information processing occurs first in the nucleus of the solitary tract (NTS). In the present study conducted in rats, we examined the synaptic characteristics of visceral afferent pathways to the central nucleus of the amygdala (CeA) in brainstem slices by recording from retrogradely labelled NTS projection neurons. We simultaneously recorded neuron pairs: one dye positive (i.e. NTS-CeA) and a second unlabelled neighbour. Graded shocks to the solitary tract (ST) always (93%) triggered EPSCs at CeA projecting NTS neurons. Half of the NTS-CeA neurons received at least one
- Published
- 2017
13. Central control of autonomic functions in health and disease
- Author
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McDougall, SJ, Muenzberg, H, Derbenev, AV, Zsombok, A, McDougall, SJ, Muenzberg, H, Derbenev, AV, and Zsombok, A
- Published
- 2015
14. Independent transmission of convergent visceral primary afferents in the solitary tract nucleus
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McDougall, SJ, Andresen, MC, McDougall, SJ, and Andresen, MC
- Abstract
Cranial primary afferents from the viscera enter the brain at the solitary tract nucleus (NTS), where their information is integrated for homeostatic reflexes. The organization of sensory inputs is poorly understood, despite its critical impact on overall reflex performance characteristics. Single afferents from the solitary tract (ST) branch within NTS and make multiple contacts onto individual neurons. Many neurons receive more than one ST input. To assess the potential interaction between converging afferents and proximal branching near to second-order neurons, we probed near the recorded soma in horizontal slices from rats with focal electrodes and minimal shocks. Remote ST shocks evoked monosynaptic excitatory postsynaptic currents (EPSCs), and nearby focal shocks also activated monosynaptic EPSCs. We tested the timing and order of stimulation to determine whether focal shocks influenced ST responses and vice versa in single neurons. Focal-evoked EPSC response profiles closely resembled ST-EPSC characteristics. Mean synaptic jitters, failure rates, depression, and phenotypic segregation by capsaicin responsiveness were indistinguishable between focal and ST-evoked EPSCs. ST-EPSCs failed to affect focal-EPSCs within neurons, indicating that release sites and synaptic terminals were functionally independent and isolated from cross talk or neurotransmitter overflow. In only one instance, focal shocks intercepted and depleted the ST axon generating evoked EPSCs. Despite large numbers of functional contacts, multiple afferents do not appear to interact, and ST axon branches may be limited to close to the soma. Thus single or multiple primary afferents and their presynaptic active release sites act independently when they contact single second-order NTS neurons.
- Published
- 2013
15. Low-fidelity GABA transmission within a dense excitatory network of the solitary tract nucleus
- Author
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McDougall, SJ, Andresen, MC, McDougall, SJ, and Andresen, MC
- Abstract
Visceral primary afferents enter the CNS at the caudal solitary tract nucleus (NTS), and activate central pathways key to autonomic and homeostatic regulation. Excitatory transmission from primary solitary tract (ST)-afferents consists of multiple contacts originating from single axons that offer a remarkably high probability of glutamate release and high safety factor for ST afferent excitation. ST afferent activation sometimes triggers polysynaptic GABAergic circuits, which feedback onto second-order NTS neurons. Although inhibitory transmission is observed at second-order neurons, much less is known about the organization and mechanisms regulating GABA transmission. Here, we used a focal pipette to deliver minimal stimulus shocks near second-order NTS neurons in rat brainstem slices and directly activated single GABAergic axons. Most minimal focal shocks activated low jitter EPSCs from single axons with characteristics resembling ST afferents. Much less commonly (9% of sites), minimal focal shocks activated monosynaptic IPSCs at fixed latency (low jitter) that often failed (30%) and had no frequency-dependent facilitation or depression. These GABA release characteristics contrasted markedly to the unfailing, large amplitudes for glutamate released during ST-EPCSs recorded from the same neurons. Surprisingly, unitary GABAergic IPSCs were only weakly calcium dependent. In some neurons, strong focal shocks evoked compound IPSCs indicating convergent summation of multiple inhibitory axons. Our studies demonstrate that second-order NTS neurons receive GABAergic transmission from a diffuse network of inhibitory axons that rely on an intrinsically less reliable and substantially weaker release apparatus than ST excitation. Effective inhibition depends on co-activation of convergent inputs to blunt excitatory drive.
- Published
- 2012
16. TRPV1 Marks Synaptic Segregation of Multiple Convergent Afferents at the Rat Medial Solitary Tract Nucleus
- Author
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Tell, F, Peters, JH, McDougall, SJ, Fawley, JA, Andresen, MC, Tell, F, Peters, JH, McDougall, SJ, Fawley, JA, and Andresen, MC
- Abstract
TRPV1 receptors are expressed on most but not all central terminals of cranial visceral afferents in the caudal solitary tract nucleus (NTS). TRPV1 is associated with unmyelinated C-fiber afferents. Both TRPV1+ and TRPV1- afferents enter NTS but their precise organization remains poorly understood. In horizontal brainstem slices, we activated solitary tract (ST) afferents and recorded ST-evoked glutamatergic excitatory synaptic currents (ST-EPSCs) under whole cell voltage clamp conditions from neurons of the medial subnucleus. Electrical shocks to the ST produced fixed latency EPSCs (jitter<200 µs) that identified direct ST afferent innervation. Graded increases in shock intensity often recruited more than one ST afferent and ST-EPSCs had consistent threshold intensity, latency to onset, and unique EPSC waveforms that characterized each unitary ST afferent contact. The TRPV1 agonist capsaicin (100 nM) blocked the evoked TRPV1+ ST-EPSCs and defined them as either TRPV1+ or TRPV1- inputs. No partial responses to capsaicin were observed so that in NTS neurons that received one or multiple (2-5) direct ST afferent inputs--all were either blocked by capsaicin or were unaltered. Since TRPV1 mediates asynchronous release following TRPV1+ ST-evoked EPSCs, we likewise found that recruiting more than one ST afferent further augmented the asynchronous response and was eliminated by capsaicin. Thus, TRPV1+ and TRPV1- afferents are completely segregated to separate NTS neurons. As a result, the TRPV1 receptor augments glutamate release only within unmyelinated afferent pathways in caudal medial NTS and our work indicates a complete separation of C-type from A-type afferent information at these first central neurons.
- Published
- 2011
17. Paired Assessment of Volatile Anesthetic Concentrations with Synaptic Actions Recorded In Vitro
- Author
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Nitabach, MN, McDougall, SJ, Peters, JH, LaBrant, L, Wang, X, Koop, DR, Andresen, MC, Nitabach, MN, McDougall, SJ, Peters, JH, LaBrant, L, Wang, X, Koop, DR, and Andresen, MC
- Abstract
The volatile anesthetic isoflurane poses a number of experimental challenges in the laboratory. Due to its rapid evaporation, the open conditions of most in vitro electrophysiological recording systems make the determination of actual isoflurane concentrations a challenge. Since the absolute anesthetic concentration in solution is directly related to efficacy, concentration measurements are important to allow comparisons between laboratory and clinical studies. In this study we quantify the sources of isoflurane loss during experimentation and describe a method for the measurement of isoflurane concentrations using gas chromatography and mass spectrometry simultaneous to in vitro electrophysiological measurements. Serial samples of perfused bath solution allowed correlation of isoflurane concentrations with ongoing biological effects. Saturated physiological solutions contained 13.4 +/- 0.2 mM isoflurane and were diluted to desired "nominal" concentrations for experiments. The perfusion system established stable isoflurane concentrations within the bath by 2 minutes. However, bath isoflurane concentrations varied substantially and unpredictably between experiments. The magnitudes of such discrepancies in isoflurane concentrations spanned clinically important levels. Our studies suggest that, despite countermeasures, solution handling significantly impacted the isoflurane content in the tissue bath. The magnitude of these discrepancies appears to necessitate systematic direct measurement of bath isoflurane concentrations during most in vitro conditions.
- Published
- 2008
18. Viscerosensory signalling to the nucleus accumbens via the solitary tract nucleus.
- Author
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McDougall SJ, Ong ZY, Heller R, Horton A, Thek KK, Choi EA, McNally GP, and Lawrence AJ
- Subjects
- Animals, Mice, Male, Rats, Rats, Sprague-Dawley, Excitatory Postsynaptic Potentials physiology, Cholecystokinin metabolism, Neural Pathways physiology, Neural Pathways metabolism, Signal Transduction physiology, Nucleus Accumbens metabolism, Nucleus Accumbens physiology, Solitary Nucleus metabolism, Solitary Nucleus physiology, Mice, Inbred C57BL
- Abstract
The nucleus of the solitary tract (NTS) receives direct viscerosensory vagal afferent input that drives autonomic reflexes, neuroendocrine function and modulates behaviour. A subpopulation of NTS neurons project to the nucleus accumbens (NAc); however, the function of this NTS-NAc pathway remains unknown. A combination of neuroanatomical tracing, slice electrophysiology and fibre photometry was used in mice and/or rats to determine how NTS-NAc neurons fit within the viscerosensory network. NTS-NAc projection neurons are predominantly located in the medial and caudal portions of the NTS with 54 ± 7% (mice) and 65 ± 3% (rat) being TH-positive, representing the A2 NTS cell group. In horizontal brainstem slices, solitary tract (ST) stimulation evoked excitatory post-synaptic currents (EPSCs) in NTS-NAc projection neurons. The majority (75%) received low-jitter, zero-failure EPSCs characteristic of monosynaptic ST afferent input that identifies them as second order to primary sensory neurons. We then examined whether NTS-NAc neurons respond to cholecystokinin (CCK, 20 μg/kg ip) in vivo in both mice and rats. Surprisingly, there was no difference in the number of activated NTS-NAc cells between CCK and saline-treated mice. In rats, just 6% of NTS-NAc cells were recruited by CCK. As NTS TH neurons are the primary source for NAc noradrenaline, we measured noradrenaline release in the NAc and showed that NAc noradrenaline levels declined in response to cue-induced reward retrieval but not foot shock. Combined, these findings suggest that high-fidelity afferent information from viscerosensory afferents reaches the NAc. These signals are likely unrelated to CCK-sensitive vagal afferents but could interact with other sensory and higher order inputs to modulate learned appetitive behaviours., (© 2024 The Author(s). Journal of Neurochemistry published by John Wiley & Sons Ltd on behalf of International Society for Neurochemistry.)
- Published
- 2024
- Full Text
- View/download PDF
19. Feeding signals inhibit fluid-satiation signals in the mouse lateral parabrachial nucleus to increase intake of highly palatable, caloric solutions.
- Author
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Aitken CM, Jaramillo JCM, Davis W, Brennan-Xie L, McDougall SJ, Lawrence AJ, and Ryan PJ
- Subjects
- Mice, Male, Female, Animals, Agouti-Related Protein metabolism, Agouti-Related Protein pharmacology, Satiation physiology, Water metabolism, Sucrose pharmacology, Ethanol pharmacology, Parabrachial Nucleus metabolism
- Abstract
Chemogenetic activation of oxytocin receptor-expressing neurons in the parabrachial nucleus (Oxtr
PBN neurons) acts as a satiation signal for water. In this research, we investigated the effect of activating OxtrPBN neurons on satiation for different types of fluids. Chemogenetic activation of OxtrPBN neurons in male and female transgenic OxtrCre mice robustly suppressed the rapid, initial (15-min) intake of several solutions after dehydration: water, sucrose, ethanol and saccharin, but only slightly decreased intake of Ensure®, a highly caloric solution (1 kcal/mL; containing 3.72 g protein, 3.27 g fat, 13.42 g carbohydrates, and 1.01 g dietary fibre per 100 mL). OxtrPBN neuron activation also suppressed cumulative, longer-term (2-h) intake of lower caloric, less palatable solutions, but not highly caloric, palatable solutions. These results suggest that OxtrPBN neurons predominantly control initial fluid-satiation responses after rehydration, but not longer-term intake of highly caloric, palatable solutions. The suppression of fluid intake was not because of anxiogenesis, but because OxtrPBN neuron activation decreased anxiety-like behaviour. To investigate the role of different PBN subdivisions on the intake of different solutions, we examined FOS as a proxy marker of PBN neuron activation. Different PBN subdivisions were activated by different solutions: the dorsolateral PBN similarly by all fluids; the external lateral PBN by caloric but not non-caloric solutions; and the central lateral PBN primarily by highly palatable solutions, suggesting PBN subdivisions regulate different aspects of fluid intake. To explore the possible mechanisms underlying the minimal suppression of Ensure® after OxtrPBN neuron activation, we demonstrated in in vitro slice recordings that the feeding-associated agouti-related peptide (AgRP) inhibited OxtrPBN neuron firing in a concentration-related manner, suggesting possible inhibition by feeding-related neurocircuitry of fluid satiation neurocircuitry. Overall, this research suggests that although palatable beverages like sucrose- and ethanol-containing beverages activate fluid satiation signals encoded by OxtrPBN neurons, these neurons can be inhibited by hunger-related signals (agouti-related peptide, AgRP), which may explain why these fluids are often consumed in excess of what is required for fluid satiation., (© 2023 The Authors. Journal of Neurochemistry published by John Wiley & Sons Ltd on behalf of International Society for Neurochemistry.)- Published
- 2023
- Full Text
- View/download PDF
20. Sites and mechanisms of action of colokinetics at dopamine, ghrelin and serotonin receptors in the rodent lumbosacral defecation centre.
- Author
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Ringuet MT, Koo A, Furness SGB, McDougall SJ, and Furness JB
- Subjects
- Humans, Rats, Animals, Mice, Receptors, Ghrelin, Rats, Sprague-Dawley, Rodentia, Defecation physiology, Ghrelin pharmacology, Tyrosine 3-Monooxygenase pharmacology, Receptors, Serotonin, Receptors, Dopamine D2, Dopamine pharmacology, Serotonin pharmacology
- Abstract
Agonists of dopamine D2 receptors (D2R), 5-hydroxytryptamine (5-HT, serotonin) receptors (5-HTR) and ghrelin receptors (GHSR) activate neurons in the lumbosacral defecation centre, and act as 'colokinetics', leading to increased propulsive colonic motility, in vivo. In the present study, we investigated which neurons in the lumbosacral defecation centre express the receptors and whether dopamine, serotonin and ghrelin receptor agonists act on the same lumbosacral preganglionic neurons (PGNs). We used whole cell electrophysiology to record responses from neurons in the lumbosacral defecation centre, following colokinetic application, and investigated their expression profiles and the chemistries of their neural inputs. Fluorescence in situ hybridisation revealed Drd2, Ghsr and Htr2C transcripts were colocalised in lumbosacral PGNs of mice, and immunohistochemistry showed that these neurons have closely associated tyrosine hydroxylase and 5-HT boutons. Previous studies showed that they do not receive ghrelin inputs. Whole cell electrophysiology in adult mice spinal cord revealed that dopamine, serotonin, α-methylserotonin and capromorelin each caused inward, excitatory currents in overlapping populations of lumbosacral PGNs. Furthermore, dopamine caused increased frequency of both IPSCs and EPSCs in a cohort of D2R neurons. Tetrodotoxin blocked the IPSCs and EPSCs, revealing a post-synaptic excitatory action of dopamine. In lumbosacral PGNs of postnatal day 7-14 rats, only dopamine's postsynaptic effects were observed. Furthermore, inward, excitatory currents evoked by dopamine were reduced by the GHSR antagonist, YIL781. We conclude that lumbosacral PGNs are the site where the action of endogenous ligands of D2R and 5-HT2R converge, and that GHSR act as a cis-modulator of D2R expressed by the same neurons. KEY POINTS: Dopamine, 5-hydroxytryptamine (5-HT, serotonin) and ghrelin (GHSR) receptor agonists increase colorectal motility and have been postulated to act at receptors on parasympathetic preganglionic neurons (PGNs) in the lumbosacral spinal cord. We aimed to determine which neurons in the lumbosacral spinal cord express dopamine, serotonin and GHSR receptors, their neural inputs, and whether agonists at these receptors excite them. We show that dopamine, serotonin and ghrelin receptor transcripts are contained in the same PGNs and that these neurons have closely associated tyrosine hydroxylase and serotonin boutons. Whole cell electrophysiology revealed that dopamine, serotonin and GHSR receptor agonists induce an inward excitatory current in overlapping populations of lumbosacral PGNs. Dopamine-induced excitation was reversed by GHSR antagonism. The present study demonstrates that lumbosacral PGNs are the site at which actions of endogenous ligands of dopamine D2 receptors and 5-HT type 2 receptors converge. Ghrelin receptors are functional, but their role appears to be as modulators of dopamine effects at D2 receptors., (© 2023 The Authors. The Journal of Physiology published by John Wiley & Sons Ltd on behalf of The Physiological Society.)
- Published
- 2023
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21. Selective transduction and photoinhibition of pre-Bötzinger complex neurons that project to the facial nucleus in rats affects nasofacial activity.
- Author
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Melo MR, Wykes AD, Connelly AA, Bassi JK, Cheung SD, McDougall SJ, Menuet C, Bathgate RAD, and Allen AM
- Subjects
- Rats, Animals, Respiratory Center, Respiration, Motor Neurons, Brain Stem, Facial Nucleus
- Abstract
The pre-Bötzinger complex (preBötC), a key primary generator of the inspiratory breathing rhythm, contains neurons that project directly to facial nucleus (7n) motoneurons to coordinate orofacial and nasofacial activity. To further understand the identity of 7n-projecting preBötC neurons, we used a combination of optogenetic viral transgenic approaches to demonstrate that selective photoinhibition of these neurons affects mystacial pad activity, with minimal effects on breathing. These effects are altered by the type of anesthetic employed and also between anesthetized and conscious states. The population of 7n-projecting preBötC neurons we transduced consisted of both excitatory and inhibitory neurons that also send collaterals to multiple brainstem nuclei involved with the regulation of autonomic activity. We show that modulation of subgroups of preBötC neurons, based on their axonal projections, is a useful strategy to improve our understanding of the mechanisms that coordinate and integrate breathing with different motor and physiological behaviors. This is of fundamental importance, given that abnormal respiratory modulation of autonomic activity and orofacial behaviors have been associated with the development and progression of diseases., Competing Interests: MM, AW, AC, JB, SC, SM, CM, RB, AA No competing interests declared, (© 2023, Melo et al.)
- Published
- 2023
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22. Analysis of the distribution of vagal afferent projections from different peripheral organs to the nucleus of the solitary tract in rats.
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Bassi JK, Connelly AA, Butler AG, Liu Y, Ghanbari A, Farmer DGS, Jenkins MW, Melo MR, McDougall SJ, and Allen AM
- Subjects
- Animals, Motor Neurons, Neurons, Afferent physiology, Nodose Ganglion, Rats, Solitary Nucleus physiology, Vagus Nerve physiology
- Abstract
Anatomical tracing studies examining the vagal system can conflate details of sensory afferent and motor efferent neurons. Here, we used a serotype of adeno-associated virus that transports retrogradely and exhibits selective tropism for vagal afferents, to map their soma location and central termination sites within the nucleus of the solitary tract (NTS). We examined the vagal sensory afferents innervating the trachea, duodenum, stomach, or heart, and in some animals, from two organs concurrently. We observed no obvious somatotopy in the somata distribution within the nodose ganglion. The central termination patterns of afferents from different organs within the NTS overlap substantially. Convergence of vagal afferent inputs from different organs onto single NTS neurons is observed. Abdominal and thoracic afferents terminate throughout the NTS, including in the rostral NTS, where the 7th cranial nerve inputs are known to synapse. To address whether the axonal labeling produced by viral transduction is so widespread because it fills axons traveling to their targets, and not just terminal fields, we labeled pre and postsynaptic elements of vagal afferents in the NTS . Vagal afferents form multiple putative synapses as they course through the NTS, with each vagal afferent neuron distributing sensory signals to multiple second-order NTS neurons. We observe little selectivity between vagal afferents from different visceral targets and NTS neurons with common neurochemical phenotypes, with afferents from different organs making close appositions with the same NTS neuron. We conclude that specific viscerosensory information is distributed widely within the NTS and that the coding of this input is probably determined by the intrinsic properties and projections of the second-order neuron., (© 2022 The Authors. The Journal of Comparative Neurology published by Wiley Periodicals LLC.)
- Published
- 2022
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23. FGF-MAPK signaling regulates human deep-layer corticogenesis.
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Gantner CW, Hunt CPJ, Niclis JC, Penna V, McDougall SJ, Thompson LH, and Parish CL
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- Cell Cycle drug effects, Cell Differentiation drug effects, Cells, Cultured, Gene Regulatory Networks drug effects, Humans, Mitogen-Activated Protein Kinases antagonists & inhibitors, Neural Stem Cells cytology, Neural Stem Cells drug effects, Neural Stem Cells metabolism, Neurogenesis drug effects, Neurons cytology, Neurons drug effects, Neurons metabolism, PAX6 Transcription Factor metabolism, Phenotype, Protein Kinase Inhibitors pharmacology, Receptors, Notch metabolism, Repressor Proteins metabolism, Tumor Suppressor Proteins metabolism, Cerebral Cortex embryology, Fibroblast Growth Factors metabolism, Mitogen-Activated Protein Kinases metabolism, Organogenesis drug effects, Signal Transduction drug effects
- Abstract
Despite heterogeneity across the six layers of the mammalian cortex, all excitatory neurons are generated from a single founder population of neuroepithelial stem cells. However, how these progenitors alter their layer competence over time remains unknown. Here, we used human embryonic stem cell-derived cortical progenitors to examine the role of fibroblast growth factor (FGF) and Notch signaling in influencing cell fate, assessing their impact on progenitor phenotype, cell-cycle kinetics, and layer specificity. Forced early cell-cycle exit, via Notch inhibition, caused rapid, near-exclusive generation of deep-layer VI neurons. In contrast, prolonged FGF2 promoted proliferation and maintained progenitor identity, delaying laminar progression via MAPK-dependent mechanisms. Inhibiting MAPK extended cell-cycle length and led to generation of layer-V CTIP2
+ neurons by repressing alternative laminar fates. Taken together, FGF/MAPK regulates the proliferative/neurogenic balance in deep-layer corticogenesis and provides a resource for generating layer-specific neurons for studying development and disease., (Copyright © 2021 The Authors. Published by Elsevier Inc. All rights reserved.)- Published
- 2021
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24. Use of a physiological reflex to standardize vagal nerve stimulation intensity improves data reproducibility in a memory extinction assay.
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Butler AG, O'Callaghan EL, Allen AM, and McDougall SJ
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- Animals, Fear, Rats, Rats, Sprague-Dawley, Reflex, Reproducibility of Results, Vagus Nerve, Vagus Nerve Stimulation
- Abstract
Background: Modulating brainstem activity, via electrical vagus nerve stimulation (VNS), influences cognitive functions, including memory. However, controlling for changes in stimulus efficacy during chronic studies, and response variability between subjects, is problematic., Objective/hypothesis: We hypothesized that recruitment of an autonomic reflex, the Hering-Breuer reflex, would provide robust confirmation of VNS efficacy. We compared this to measurement of electrode resistance over time. We also examined whether VNS modulates contextual memory extinction., Methods: Electrodes for VNS and diaphragm electromyography recording were implanted into anesthetized Sprague Dawley rats. When conscious, we measured the electrode resistance as well as the minimum VNS current required to evoke the Hering-Breuer reflex, before, and after, an inhibitory avoidance assay - a two chamber, dark/light model, where the dark compartment was paired with an aversive foot shock. The extinction of this contextual memory was assessed in sham and VNS treated rats, with VNS administered for 30 s at 1.5 times the Hering-Breuer reflex threshold during extinction memory formation., Results: Assessment of VNS-evoked Hering-Breuer reflex successfully identified defective electrodes. VNS accelerated extinction memory and decreased multiple physiological metrics of fear expression. We observed an inverse relationship between memory extinction and respiratory rate during the behavioural assay. Additionally, no current - response relationship between VNS and extinction memory formation was established., Conclusion: These data demonstrate that reliable, experimental VNS studies can be produced by verifying reflex initiation as a consequence of stimulation. Further, studies could be standardised by indexing stimulator efficacy to initiation of autonomic reflexes., Competing Interests: Declaration of competing interest The authors declare no competing financial interests. Supported by grants from the Australian Research Council (Discovery Project 170,104,861 and 170,104,582, SJM &AMA), the National Health and Medical Research Council of Australia (APP1120477, AMA), University of Melbourne Research Grant Support Scheme (SJM) and the Victorian Government’s Operational Infrastructure Support Program (Florey). All authors have made substantial contributions to all of the following: (1) the conception and design of the study, or acquisition of data, or analysis and interpretation of data, (2) drafting the article or revising it critically for important intellectual content, (3) final approval of the version to be submitted., (Copyright © 2021 The Authors. Published by Elsevier Inc. All rights reserved.)
- Published
- 2021
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25. Selective optogenetic stimulation of efferent fibers in the vagus nerve of a large mammal.
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Booth LC, Yao ST, Korsak A, Farmer DGS, Hood SG, McCormick D, Boesley Q, Connelly AA, McDougall SJ, Korim WS, Guild SJ, Mastitskaya S, Le P, Teschemacher AG, Kasparov S, Ackland GL, Malpas SC, McAllen RM, Allen AM, May CN, and Gourine AV
- Subjects
- Animals, Mammals, Motor Neurons, Rats, Sheep, Vagus Nerve, Optogenetics, Vagus Nerve Stimulation
- Abstract
Background: Electrical stimulation applied to individual organs, peripheral nerves, or specific brain regions has been used to treat a range of medical conditions. In cardiovascular disease, autonomic dysfunction contributes to the disease progression and electrical stimulation of the vagus nerve has been pursued as a treatment for the purpose of restoring the autonomic balance. However, this approach lacks selectivity in activating function- and organ-specific vagal fibers and, despite promising results of many preclinical studies, has so far failed to translate into a clinical treatment of cardiovascular disease., Objective: Here we report a successful application of optogenetics for selective stimulation of vagal efferent activity in a large animal model (sheep)., Methods and Results: Twelve weeks after viral transduction of a subset of vagal motoneurons, strong axonal membrane expression of the excitatory light-sensitive ion channel ChIEF was achieved in the efferent projections innervating thoracic organs and reaching beyond the level of the diaphragm. Blue laser or LED light (>10 mW mm
-2 ; 1 ms pulses) applied to the cervical vagus triggered precisely timed, strong bursts of efferent activity with evoked action potentials propagating at speeds of ∼6 m s-1 ., Conclusions: These findings demonstrate that in species with a large, multi-fascicled vagus nerve, it is possible to stimulate a specific sub-population of efferent fibers using light at a site remote from the vector delivery, marking an important step towards eventual clinical use of optogenetic technology for autonomic neuromodulation., Competing Interests: Declaration of competing interest All authors declare no conflict of interest., (Copyright © 2020 The Author(s). Published by Elsevier Inc. All rights reserved.)- Published
- 2021
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26. A Chemogenetic Tool that Enables Functional Neural Circuit Analysis.
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Ngo HB, Melo MR, Layfield S, Connelly AA, Bassi JK, Xie L, Menuet C, McDougall SJ, Bathgate RAD, and Allen AM
- Subjects
- Amino Acid Sequence, Animals, Blood Pressure, Body Weight, CHO Cells, Cricetulus, Electrophysiological Phenomena, HEK293 Cells, Homeodomain Proteins, Homeostasis, Humans, Neurons, Afferent physiology, Neuropeptides chemistry, Neuropeptides metabolism, Rats, Inbred SHR, Rats, Sprague-Dawley, Rats, Transgenic, Receptors, Cell Surface metabolism, Solitary Nucleus physiology, Synapses metabolism, Transgenes, Vagus Nerve physiology, Nerve Net physiology, Neurons physiology
- Abstract
Chemogenetics enables manipulation of neuronal activity in experimental animals. While providing information about the transduced neuron expressing a ligand-activated molecule, chemogenetics does not provide understanding about the antecedent circuit that drives that neuron's activity. For current approaches, this is not feasible, because the activating molecules are not genetically encoded. The insect allatostatin/allatostatin receptor system, a highly specific, powerful inhibitory chemogenetic approach, has this advantage, because the ligand, being a peptide, is genetically encoded. We developed viral vector-based systems to express biologically active allatostatin in neurons in vivo and allatostatin receptors in subpopulations of postsynaptic neurons. We demonstrate that activity-dependent release of allatostatin induces inhibition of allatostatin receptor-expressing neurons. We validate the approach in the vagal viscerosensory system where inhibitory, rather than the usual excitatory, viscerosensory input leads to sustained decreases in baroreceptor reflex sensitivity and bodyweight., Competing Interests: Declaration of Interests The authors declare no competing interests., (Copyright © 2020 The Author(s). Published by Elsevier Inc. All rights reserved.)
- Published
- 2020
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27. PreBötzinger complex neurons drive respiratory modulation of blood pressure and heart rate.
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Menuet C, Connelly AA, Bassi JK, Melo MR, Le S, Kamar J, Kumar NN, McDougall SJ, McMullan S, and Allen AM
- Subjects
- Action Potentials, Animals, Chloride Channels physiology, Excitatory Postsynaptic Potentials, Male, Medulla Oblongata physiology, Optogenetics, Rats, Rats, Sprague-Dawley, Respiration, Blood Pressure, Heart Rate, Neurons physiology, Respiratory Center physiology
- Abstract
Heart rate and blood pressure oscillate in phase with respiratory activity. A component of these oscillations is generated centrally, with respiratory neurons entraining the activity of pre-sympathetic and parasympathetic cardiovascular neurons. Using a combination of optogenetic inhibition and excitation in vivo and in situ in rats, as well as neuronal tracing, we demonstrate that preBötzinger Complex (preBötC) neurons, which form the kernel for inspiratory rhythm generation, directly modulate cardiovascular activity. Specifically, inhibitory preBötC neurons modulate cardiac parasympathetic neuron activity whilst excitatory preBötC neurons modulate sympathetic vasomotor neuron activity, generating heart rate and blood pressure oscillations in phase with respiration. Our data reveal yet more functions entrained to the activity of the preBötC, with a role in generating cardiorespiratory oscillations. The findings have implications for cardiovascular pathologies, such as hypertension and heart failure, where respiratory entrainment of heart rate is diminished and respiratory entrainment of blood pressure exaggerated., Competing Interests: CM, AC, JB, MM, SL, JK, NK, SM, SM, AA No competing interests declared, (© 2020, Menuet et al.)
- Published
- 2020
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28. Characterization of the relaxin family peptide receptor 3 system in the mouse bed nucleus of the stria terminalis.
- Author
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Ch'ng SS, Fu J, Brown RM, Smith CM, Hossain MA, McDougall SJ, and Lawrence AJ
- Subjects
- Animals, Calbindins metabolism, Calcium metabolism, Calcium-Calmodulin-Dependent Protein Kinase Type 2 metabolism, Corticotropin-Releasing Hormone metabolism, Female, Male, Membrane Potentials physiology, Mice, Transgenic, Neural Inhibition physiology, RNA, Messenger metabolism, Receptors, G-Protein-Coupled genetics, Stress, Psychological metabolism, Tissue Culture Techniques, Vesicular Glutamate Transport Protein 2 metabolism, gamma-Aminobutyric Acid metabolism, Neurons cytology, Neurons metabolism, Receptors, G-Protein-Coupled metabolism, Septal Nuclei cytology, Septal Nuclei metabolism
- Abstract
The bed nucleus of the stria terminalis (BNST) is a critical node involved in stress and reward-related behaviors. Relaxin family peptide receptor 3 (RXFP3) signaling in the BNST has been implicated in stress-induced alcohol seeking behavior. However, the neurochemical phenotype and connectivity of BNST RXFP3-expressing (RXFP3+) cells have yet to be elucidated. We interrogated the molecular signature and electrophysiological properties of BNST RXFP3+ neurons using a RXFP3-Cre reporter mouse line. BNST RXFP3+ cells are circumscribed to the dorsal BNST (dBNST) and are neurochemically heterogeneous, comprising a mix of inhibitory and excitatory neurons. Immunohistochemistry revealed that ~48% of BNST RXFP3+ neurons are GABAergic, and a quarter of these co-express the calcium-binding protein, calbindin. A subset of BNST RXFP3+ cells (~41%) co-express CaMKIIα, suggesting this subpopulation of BNST RXFP3+ neurons are excitatory. Corroborating this, RNAscope® revealed that ~35% of BNST RXFP3+ cells express vVGluT2 mRNA, indicating a subpopulation of RXFP3+ neurons are glutamatergic. RXFP3+ neurons show direct hyperpolarization to bath application of a selective RXFP3 agonist, RXFP3-A2, while around 50% of cells were depolarised by exogenous corticotrophin releasing factor. In behaviorally naive mice the majority of RXFP3+ neurons were Type II cells exhibiting I
h and T type calcium mediated currents. However, chronic swim stress caused persistent plasticity, decreasing the proportion of neurons that express these channels. These studies are the first to characterize the BNST RXFP3 system in mouse and lay the foundation for future functional studies appraising the role of the murine BNST RXFP3 system in more complex behaviors., (© 2019 Wiley Periodicals, Inc.)- Published
- 2019
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29. Extensive Inhibitory Gating of Viscerosensory Signals by a Sparse Network of Somatostatin Neurons.
- Author
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Thek KR, Ong SJM, Carter DC, Bassi JK, Allen AM, and McDougall SJ
- Subjects
- Animals, Feedback, Physiological, Female, Glutamate Decarboxylase genetics, Glutamate Decarboxylase physiology, Glycine physiology, Interneurons physiology, Male, Mice, Nerve Net cytology, Photic Stimulation, Rats, Rats, Sprague-Dawley, Solitary Nucleus cytology, Solitary Nucleus physiology, Visceral Afferents physiology, gamma-Aminobutyric Acid physiology, Nerve Net physiology, Neurons physiology, Sensation physiology, Sensory Gating physiology, Somatostatin physiology
- Abstract
Integration and modulation of primary afferent sensory information begins at the first terminating sites within the CNS, where central inhibitory circuits play an integral role. Viscerosensory information is conveyed to the nucleus of the solitary tract (NTS) where it initiates neuroendocrine, behavioral, and autonomic reflex responses that ensure optimal internal organ function. This excitatory input is modulated by diverse, local inhibitory interneurons, whose functions are not clearly understood. Here we show that, in male rats, 65% of somatostatin-expressing (SST) NTS neurons also express GAD67, supporting their likely role as inhibitory interneurons. Using whole-cell recordings of NTS neurons, from horizontal brainstem slices of male and female SST-yellow fluorescent protein (YFP) and SST-channelrhodopsin 2 (ChR2)-YFP mice, we quantified the impact of SST-NTS neurons on viscerosensory processing. Light-evoked excitatory photocurrents were reliably obtained from SST-ChR2-YFP neurons ( n = 16) and the stimulation-response characteristics determined. Most SST neurons (57%) received direct input from solitary tract (ST) afferents, indicating that they form part of a feedforward circuit. All recorded SST-negative NTS neurons ( n = 72) received SST-ChR2 input. ChR2-evoked PSCs were largely inhibitory and, in contrast to previous reports, were mediated by both GABA and glycine. When timed to coincide, the ChR2-activated SST input suppressed ST-evoked action potentials at second-order NTS neurons, demonstrating strong modulation of primary viscerosensory input. These data indicate that the SST inhibitory network innervates broadly within the NTS, with the potential to gate viscerosensory input to powerfully alter autonomic reflex function and other behaviors. SIGNIFICANCE STATEMENT Sensory afferent input is modulated according to state. For example the baroreflex is altered during a stress response or exercise, but the basic mechanisms underpinning this sensory modulation are not fully understood in any sensory system. Here we demonstrate that the neuronal processing of viscerosensory information begins with synaptic gating at the first central synapse with second-order neurons in the NTS. These data reveal that the somatostatin subclass of inhibitory interneurons are driven by visceral sensory input to play a major role in gating viscerosensory signals, placing them within a feedforward circuit within the NTS., (Copyright © 2019 the authors.)
- Published
- 2019
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30. The intersection of stress and reward: BNST modulation of aversive and appetitive states.
- Author
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Ch'ng S, Fu J, Brown RM, McDougall SJ, and Lawrence AJ
- Subjects
- Animals, Humans, Nerve Net metabolism, Nerve Net physiopathology, Neurons physiology, Appetitive Behavior physiology, Neurochemistry, Septal Nuclei metabolism, Septal Nuclei pathology, Septal Nuclei physiology, Stress, Psychological pathology, Stress, Psychological physiopathology, Stress, Psychological psychology
- Abstract
The bed nucleus of the stria terminalis (BNST) is widely acknowledged as a brain structure that regulates stress and anxiety states, as well as aversive and appetitive behaviours. The diverse roles of the BNST are afforded by its highly modular organisation, neurochemical heterogeneity, and complex intrinsic and extrinsic circuitry. There has been growing interest in the BNST in relation to psychopathologies such as anxiety and addiction. Although research on the human BNST is still in its infancy, there have been extensive preclinical studies examining the molecular signature and hodology of the BNST and their involvement in stress and reward seeking behaviour. This review examines the neurochemical phenotype and connectivity of the BNST, as well as electrophysiological correlates of plasticity in the BNST mediated by stress and/or drugs of abuse., (Copyright © 2018 Elsevier Inc. All rights reserved.)
- Published
- 2018
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31. Viscerosensory input drives angiotensin II type 1A receptor-expressing neurons in the solitary tract nucleus.
- Author
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Carter DA, Guo H, Connelly AA, Bassi JK, Fong AY, Allen AM, and McDougall SJ
- Subjects
- Angiotensin II pharmacology, Animals, Genes, Reporter, Glutamic Acid metabolism, Green Fluorescent Proteins genetics, Green Fluorescent Proteins metabolism, Membrane Potentials, Mice, Transgenic, Nerve Fibers, Myelinated metabolism, Nerve Fibers, Unmyelinated metabolism, Neurons, Afferent drug effects, Promoter Regions, Genetic, Receptor, Angiotensin, Type 1 agonists, Receptor, Angiotensin, Type 1 genetics, Solitary Nucleus cytology, Solitary Nucleus drug effects, Synaptic Transmission, Neurons, Afferent metabolism, Receptor, Angiotensin, Type 1 metabolism, Solitary Nucleus metabolism
- Abstract
Homeostatic regulation of visceral organ function requires integrated processing of neural and neurohormonal sensory signals. The nucleus of the solitary tract (NTS) is the primary sensory nucleus for cranial visceral sensory afferents. Angiotensin II (ANG II) is known to modulate peripheral visceral reflexes, in part, by activating ANG II type 1A receptors (AT
1A R) in the NTS. AT1A R-expressing NTS neurons occur throughout the NTS with a defined subnuclear distribution, and most of these neurons are depolarized by ANG II. In this study we determined whether AT1A R-expressing NTS neurons receive direct visceral sensory input, and whether this input is modulated by ANG II. Using AT1A R-GFP mice to make targeted whole cell recordings from AT1A R-expressing NTS neurons, we demonstrate that two-thirds (37 of 56) of AT1A R-expressing neurons receive direct excitatory, visceral sensory input. In half of the neurons tested (4 of 8) the excitatory visceral sensory input was significantly reduced by application of the transient receptor potential vallinoid type 1 receptor agonist, capsaicin, indicating AT1A R-expressing neurons can receive either C- or A-fiber-mediated input. Application of ANG II to a subset of second-order AT1A R-expressing neurons did not affect spontaneous, evoked, or asynchronous glutamate release from visceral sensory afferents. Thus it is unlikely that AT1A R-expressing viscerosensory neurons terminate on AT1A R-expressing NTS neurons. Our data suggest that ANG II is likely to modulate multiple visceral sensory modalities by altering the excitability of second-order AT1A R-expressing NTS neurons.- Published
- 2018
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32. Pharmacogenetic stimulation of neuronal activity increases myelination in an axon-specific manner.
- Author
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Mitew S, Gobius I, Fenlon LR, McDougall SJ, Hawkes D, Xing YL, Bujalka H, Gundlach AL, Richards LJ, Kilpatrick TJ, Merson TD, and Emery B
- Subjects
- Animals, Brain cytology, Brain growth & development, Cell Differentiation, Cell Proliferation, Clozapine pharmacology, Female, Male, Mice, Mice, Inbred C57BL, Mice, Transgenic, Oligodendroglia cytology, Axons metabolism, Brain metabolism, Myelin Sheath metabolism, Nerve Fibers, Myelinated metabolism, Neural Stem Cells cytology
- Abstract
Mounting evidence suggests that neuronal activity influences myelination, potentially allowing for experience-driven modulation of neural circuitry. The degree to which neuronal activity is capable of regulating myelination at the individual axon level is unclear. Here we demonstrate that stimulation of somatosensory axons in the mouse brain increases proliferation and differentiation of oligodendrocyte progenitor cells (OPCs) within the underlying white matter. Stimulated axons display an increased probability of being myelinated compared to neighboring non-stimulated axons, in addition to being ensheathed with thicker myelin. Conversely, attenuating neuronal firing reduces axonal myelination in a selective activity-dependent manner. Our findings reveal that the process of selecting axons for myelination is strongly influenced by the relative activity of individual axons within a population. These observed cellular changes are consistent with the emerging concept that adaptive myelination is a key mechanism for the fine-tuning of neuronal circuitry in the mammalian CNS.
- Published
- 2018
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33. Functional and neurochemical characterization of angiotensin type 1A receptor-expressing neurons in the nucleus of the solitary tract of the mouse.
- Author
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Carter DA, Choong YT, Connelly AA, Bassi JK, Hunter NO, Thongsepee N, Llewellyn-Smith IJ, Fong AY, McDougall SJ, and Allen AM
- Subjects
- Animals, Female, Green Fluorescent Proteins metabolism, Male, Mice, Mice, Transgenic, Neurons cytology, Patch-Clamp Techniques, Promoter Regions, Genetic, Receptor, Angiotensin, Type 1 genetics, Solitary Nucleus cytology, Tyrosine 3-Monooxygenase metabolism, Neurons metabolism, Receptor, Angiotensin, Type 1 metabolism, Solitary Nucleus metabolism
- Abstract
Angiotensin II acts via two main receptors within the central nervous system, with the type 1A receptor (AT
1A R) most widely expressed in adult neurons. Activation of the AT1 R in the nucleus of the solitary tract (NTS), the principal nucleus receiving central synapses of viscerosensory afferents, modulates cardiovascular reflexes. Expression of the AT1 R occurs in high density within the NTS of most mammals, including humans, but the fundamental electrophysiological and neurochemical characteristics of the AT1A R-expressing NTS neurons are not known. To address this, we have used a transgenic mouse, in which the AT1A R promoter drives expression of green fluorescent protein (GFP). Approximately one-third of AT1A R-expressing neurons express the catecholamine-synthetic enzyme tyrosine hydroxylase (TH), and a subpopulation of these stained for the transcription factor paired-like homeobox 2b (Phox2b). A third group, comprising approximately two-thirds of the AT1A R-expressing NTS neurons, showed Phox2b immunoreactivity alone. A fourth group in the ventral subnucleus expressed neither TH nor Phox2b. In whole cell recordings from slices in vitro, AT1A R-GFP neurons exhibited voltage-activated potassium currents, including the transient outward current and the M-type potassium current. In two different mouse strains, both AT1A R-GFP neurons and TH-GFP neurons showed similar AT1A R-mediated depolarizing responses to superfusion with angiotensin II. These data provide a comprehensive description of AT1A R-expressing neurons in the NTS and increase our understanding of the complex actions of this neuropeptide in the modulation of viscerosensory processing., (Copyright © 2017 the American Physiological Society.)- Published
- 2017
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34. Polysialic Acid Regulates Sympathetic Outflow by Facilitating Information Transfer within the Nucleus of the Solitary Tract.
- Author
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Bokiniec P, Shahbazian S, McDougall SJ, Berning BA, Cheng D, Llewellyn-Smith IJ, Burke PGR, McMullan S, Mühlenhoff M, Hildebrandt H, Braet F, Connor M, Packer NH, and Goodchild AK
- Subjects
- Animals, Excitatory Postsynaptic Potentials physiology, Male, Rats, Rats, Sprague-Dawley, Tissue Distribution, Afferent Pathways physiology, Nerve Net physiology, Neuronal Plasticity physiology, Sialic Acids metabolism, Solitary Nucleus physiology, Sympathetic Nervous System physiology
- Abstract
Expression of the large extracellular glycan, polysialic acid (polySia), is restricted in the adult, to brain regions exhibiting high levels of plasticity or remodeling, including the hippocampus, prefrontal cortex, and the nucleus of the solitary tract (NTS). The NTS, located in the dorsal brainstem, receives constant viscerosensory afferent traffic as well as input from central regions controlling sympathetic nerve activity, respiration, gastrointestinal functions, hormonal release, and behavior. Our aims were to determine the ultrastructural location of polySia in the NTS and the functional effects of enzymatic removal of polySia, both in vitro and in vivo polySia immunoreactivity was found throughout the adult rat NTS. Electron microscopy demonstrated polySia at sites that influence neurotransmission: the extracellular space, fine astrocytic processes, and neuronal terminals. Removing polySia from the NTS had functional consequences. Whole-cell electrophysiological recordings revealed altered intrinsic membrane properties, enhancing voltage-gated K
+ currents and increasing intracellular Ca2+ Viscerosensory afferent processing was also disrupted, dampening low-frequency excitatory input and potentiating high-frequency sustained currents at second-order neurons. Removal of polySia in the NTS of anesthetized rats increased sympathetic nerve activity, whereas functionally related enzymes that do not alter polySia expression had little effect. These data indicate that polySia is required for the normal transmission of information through the NTS and that changes in its expression alter sympathetic outflow. polySia is abundant in multiple but discrete brain regions, including sensory nuclei, in both the adult rat and human, where it may regulate neuronal function by mechanisms identified here. SIGNIFICANCE STATEMENT All cells are coated in glycans (sugars) existing predominantly as glycolipids, proteoglycans, or glycoproteins formed by the most complex form of posttranslational modification, glycosylation. How these glycans influence brain function is only now beginning to be elucidated. The adult nucleus of the solitary tract has abundant polysialic acid (polySia) and is a major site of integration, receiving viscerosensory information which controls critical homeostatic functions. Our data reveal that polySia is a determinant of neuronal behavior and excitatory transmission in the nucleus of the solitary tract, regulating sympathetic nerve activity. polySia is abundantly expressed at distinct brain sites in adult, including major sensory nuclei, suggesting that sensory transmission may also be influenced via mechanisms described here. These findings hint at the importance of elucidating how other glycans influence neural function., (Copyright © 2017 the authors 0270-6474/17/376559-17$15.00/0.)- Published
- 2017
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35. Efficiently Specified Ventral Midbrain Dopamine Neurons from Human Pluripotent Stem Cells Under Xeno-Free Conditions Restore Motor Deficits in Parkinsonian Rodents.
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Niclis JC, Gantner CW, Alsanie WF, McDougall SJ, Bye CR, Elefanty AG, Stanley EG, Haynes JM, Pouton CW, Thompson LH, and Parish CL
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- Animals, Cell Differentiation, Cells, Cultured, Cryopreservation, Dopamine metabolism, Feeder Cells cytology, Fibroblasts cytology, Humans, Mice, Parkinson Disease pathology, Phenotype, Rats, Dopaminergic Neurons cytology, Dopaminergic Neurons transplantation, Mesencephalon cytology, Motor Activity, Parkinson Disease physiopathology, Parkinson Disease therapy, Pluripotent Stem Cells cytology
- Abstract
Recent studies have shown evidence for the functional integration of human pluripotent stem cell (hPSC)-derived ventral midbrain dopamine (vmDA) neurons in animal models of Parkinson's disease. Although these cells present a sustainable alternative to fetal mesencephalic grafts, a number of hurdles require attention prior to clinical translation. These include the persistent use of xenogeneic reagents and challenges associated with scalability and storage of differentiated cells. In this study, we describe the first fully defined feeder- and xenogeneic-free protocol for the generation of vmDA neurons from hPSCs and utilize two novel reporter knock-in lines (LMX1A-eGFP and PITX3-eGFP) for in-depth in vitro and in vivo tracking. Across multiple embryonic and induced hPSC lines, this "next generation" protocol consistently increases both the yield and proportion of vmDA neural progenitors (OTX2/FOXA2/LMX1A) and neurons (FOXA2/TH/PITX3) that display classical vmDA metabolic and electrophysiological properties. We identify the mechanism underlying these improvements and demonstrate clinical applicability with the first report of scalability and cryopreservation of bona fide vmDA progenitors at a time amenable to transplantation. Finally, transplantation of xeno-free vmDA progenitors from LMX1A- and PITX3-eGFP reporter lines into Parkinsonian rodents demonstrates improved engraftment outcomes and restoration of motor deficits. These findings provide important and necessary advancements for the translation of hPSC-derived neurons into the clinic. Stem Cells Translational Medicine 2017;6:937-948., (© 2016 The Authors Stem Cells Translational Medicine published by Wiley Periodicals, Inc. on behalf of AlphaMed Press.)
- Published
- 2017
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36. Dedicated C-fibre viscerosensory pathways to central nucleus of the amygdala.
- Author
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McDougall SJ, Guo H, and Andresen MC
- Subjects
- Animals, Male, Neurons physiology, Rats, Sprague-Dawley, Central Amygdaloid Nucleus physiology, Nerve Fibers, Unmyelinated physiology, Solitary Nucleus physiology
- Abstract
Key Points: Emotions are accompanied by concordant changes in visceral function, including cardiac output, respiration and digestion. One major forebrain integrator of emotional responses, the amygdala, is considered to rely on embedded visceral afferent information, although few details are known. In the present study, we retrogradely transported dye from the central nucleus of the amygdala (CeA) to identify CeA-projecting nucleus of the solitary tract (NTS) neurons for synaptic characterization and compared them with unlabelled, near-neighboor NTS neurons. Solitary tract (ST) afferents converged onto NTS-CeA second-order sensory neurons in greater numbers, as well as indirectly via polysynaptic pathways. Unexpectedly, all mono- and polysynaptic ST afferent pathways to NTS-CeA neurons were organized exclusively as either transient receptor potential cation channel subfamily V member 1 (TRPV1)-sensitive or TRPV1-resistant, regardless of whether intervening neurons were excitatory or inhibitory. This strict sorting provides viscerosensory signals to CeA about visceral conditions with respect to being either 'normal' via A-fibres or 'alarm' via TRPV1 expressing C-fibres and, accordingly, this pathway organization probably encodes interoceptive status., Abstract: Emotional state is impacted by changes in visceral function, including blood pressure, breathing and digestion. A main line of viscerosensory information processing occurs first in the nucleus of the solitary tract (NTS). In the present study conducted in rats, we examined the synaptic characteristics of visceral afferent pathways to the central nucleus of the amygdala (CeA) in brainstem slices by recording from retrogradely labelled NTS projection neurons. We simultaneously recorded neuron pairs: one dye positive (i.e. NTS-CeA) and a second unlabelled neighbour. Graded shocks to the solitary tract (ST) always (93%) triggered EPSCs at CeA projecting NTS neurons. Half of the NTS-CeA neurons received at least one primary afferent input (classed 'second order') indicating that viscerosensory information arrives at the CeA conveyed via a pathway involving as few as two synapses. The remaining NTS-CeA neurons received viscerosensory input only via polysynaptic pathways. By contrast, ∼3/4 of unlabelled neighbouring neurons were directly connected to ST. NTS-CeA neurons received greater numbers of ST-related inputs compared to unlabelled NTS neurons, indicating that highly convergent viscerosensory signals reach the CeA. Remarkably, despite multifibre convergence, all single NTS-CeA neurons received inputs derived from only unmyelinated afferents [transient receptor potential cation channel subfamily V member 1 (TRPV1) expressing C-fibres] or only non-TRPV1 ST afferent inputs, and never a combination of both. Such segregation means that visceral afferent information followed separate lines to reach the CeA. Their very different physiological activation profiles mean that these parallel visceral afferent pathways encode viscerosensory signals to the amygdala that may provide interoceptive assessments to impact on behaviours., (© 2016 The Authors. The Journal of Physiology © 2016 The Physiological Society.)
- Published
- 2017
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37. Nucleus incertus promotes cortical desynchronization and behavioral arousal.
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Ma S, Allocca G, Ong-Pålsson EK, Singleton CE, Hawkes D, McDougall SJ, Williams SJ, Bathgate RA, and Gundlach AL
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- Animals, Avoidance Learning, Brain Waves, Conditioning, Classical physiology, Electroencephalography, Fear physiology, GABAergic Neurons metabolism, Male, Motor Activity, Rats, Rats, Sprague-Dawley, Arousal, Behavior, Animal physiology, Cortical Synchronization, Raphe Nuclei physiology
- Abstract
Arousal and vigilance are essential for survival and relevant regulatory neural circuits lie within the brainstem, hypothalamus and forebrain. The nucleus incertus (NI) is a distinct site within the pontine periventricular gray, containing a substantial population of GABAergic neurons with long-range, ascending projections. Existing neuroanatomical data and functional studies in anesthetized rats, suggest the NI is a central component of a midline behavioral control network well positioned to modulate arousal, vigilance and exploratory navigation, yet none of these roles have been established experimentally. We used a chemogenetic approach-clozapine-N-oxide (CNO) activation of virally delivered excitatory hM3Dq-DREADDs-to activate the NI in rats and examined the behavioral and physiological effects, relative to effects in naïve rats and appropriate viral-treated controls. hM3Dq activation by CNO resulted in long-lasting depolarization of NI neurons with action potentials, in vitro. Peripheral injection of CNO significantly increased c-Fos immunoreactivity in the NI and promoted cortical electroencephalograph (EEG) desynchronization. These brain changes were associated with heightened arousal, and increased locomotor activity in the homecage and in a novel environment. Furthermore, NI activation altered responses in a fear conditioning paradigm, reflected by increased head-scanning, vigilant behaviors during conditioned fear recall. These findings provide direct evidence that the NI promotes general arousal via a broad behavioral activation circuit and support early hypotheses, based on its connectivity, that the NI is a modulator of cognition and attention, and emotional and motivated behaviors.
- Published
- 2017
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38. Central control of autonomic functions in health and disease.
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McDougall SJ, Münzberg H, Derbenev AV, and Zsombok A
- Published
- 2015
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39. Independent transmission of convergent visceral primary afferents in the solitary tract nucleus.
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McDougall SJ and Andresen MC
- Subjects
- Afferent Pathways cytology, Afferent Pathways physiology, Animals, Rats, Rats, Sprague-Dawley, Solitary Nucleus cytology, Excitatory Postsynaptic Potentials, Neurons physiology, Solitary Nucleus physiology, Viscera innervation
- Abstract
Cranial primary afferents from the viscera enter the brain at the solitary tract nucleus (NTS), where their information is integrated for homeostatic reflexes. The organization of sensory inputs is poorly understood, despite its critical impact on overall reflex performance characteristics. Single afferents from the solitary tract (ST) branch within NTS and make multiple contacts onto individual neurons. Many neurons receive more than one ST input. To assess the potential interaction between converging afferents and proximal branching near to second-order neurons, we probed near the recorded soma in horizontal slices from rats with focal electrodes and minimal shocks. Remote ST shocks evoked monosynaptic excitatory postsynaptic currents (EPSCs), and nearby focal shocks also activated monosynaptic EPSCs. We tested the timing and order of stimulation to determine whether focal shocks influenced ST responses and vice versa in single neurons. Focal-evoked EPSC response profiles closely resembled ST-EPSC characteristics. Mean synaptic jitters, failure rates, depression, and phenotypic segregation by capsaicin responsiveness were indistinguishable between focal and ST-evoked EPSCs. ST-EPSCs failed to affect focal-EPSCs within neurons, indicating that release sites and synaptic terminals were functionally independent and isolated from cross talk or neurotransmitter overflow. In only one instance, focal shocks intercepted and depleted the ST axon generating evoked EPSCs. Despite large numbers of functional contacts, multiple afferents do not appear to interact, and ST axon branches may be limited to close to the soma. Thus single or multiple primary afferents and their presynaptic active release sites act independently when they contact single second-order NTS neurons.
- Published
- 2013
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40. Low-fidelity GABA transmission within a dense excitatory network of the solitary tract nucleus.
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McDougall SJ and Andresen MC
- Subjects
- Afferent Pathways physiology, Animals, Axons physiology, Calcium metabolism, Excitatory Amino Acid Antagonists pharmacology, GABA Antagonists pharmacology, Glutamic Acid metabolism, Nerve Net, Neurons, Afferent physiology, Rats, Rats, Sprague-Dawley, Excitatory Postsynaptic Potentials, GABAergic Neurons physiology, Solitary Nucleus physiology, Synaptic Transmission, gamma-Aminobutyric Acid metabolism
- Abstract
Visceral primary afferents enter the CNS at the caudal solitary tract nucleus (NTS), and activate central pathways key to autonomic and homeostatic regulation. Excitatory transmission from primary solitary tract (ST)-afferents consists of multiple contacts originating from single axons that offer a remarkably high probability of glutamate release and high safety factor for ST afferent excitation. ST afferent activation sometimes triggers polysynaptic GABAergic circuits, which feedback onto second-order NTS neurons. Although inhibitory transmission is observed at second-order neurons, much less is known about the organization and mechanisms regulating GABA transmission. Here, we used a focal pipette to deliver minimal stimulus shocks near second-order NTS neurons in rat brainstem slices and directly activated single GABAergic axons. Most minimal focal shocks activated low jitter EPSCs from single axons with characteristics resembling ST afferents. Much less commonly (9% of sites), minimal focal shocks activated monosynaptic IPSCs at fixed latency (low jitter) that often failed (30%) and had no frequency-dependent facilitation or depression. These GABA release characteristics contrasted markedly to the unfailing, large amplitudes for glutamate released during ST-EPCSs recorded from the same neurons. Surprisingly, unitary GABAergic IPSCs were only weakly calcium dependent. In some neurons, strong focal shocks evoked compound IPSCs indicating convergent summation of multiple inhibitory axons. Our studies demonstrate that second-order NTS neurons receive GABAergic transmission from a diffuse network of inhibitory axons that rely on an intrinsically less reliable and substantially weaker release apparatus than ST excitation. Effective inhibition depends on co-activation of convergent inputs to blunt excitatory drive.
- Published
- 2012
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41. TRPV1 marks synaptic segregation of multiple convergent afferents at the rat medial solitary tract nucleus.
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Peters JH, McDougall SJ, Fawley JA, and Andresen MC
- Subjects
- Afferent Pathways drug effects, Animals, Brain Stem cytology, Brain Stem drug effects, Capsaicin pharmacology, Electric Stimulation, Glutamic Acid metabolism, Male, Neurons cytology, Patch-Clamp Techniques, Rats, Rats, Sprague-Dawley, Receptors, Glutamate metabolism, Sensory System Agents pharmacology, Solitary Nucleus cytology, Synaptic Transmission drug effects, Visceral Afferents drug effects, Brain Stem metabolism, Excitatory Postsynaptic Potentials physiology, Neurons drug effects, Neurons metabolism, Solitary Nucleus metabolism, TRPV Cation Channels metabolism
- Abstract
TRPV1 receptors are expressed on most but not all central terminals of cranial visceral afferents in the caudal solitary tract nucleus (NTS). TRPV1 is associated with unmyelinated C-fiber afferents. Both TRPV1+ and TRPV1- afferents enter NTS but their precise organization remains poorly understood. In horizontal brainstem slices, we activated solitary tract (ST) afferents and recorded ST-evoked glutamatergic excitatory synaptic currents (ST-EPSCs) under whole cell voltage clamp conditions from neurons of the medial subnucleus. Electrical shocks to the ST produced fixed latency EPSCs (jitter<200 µs) that identified direct ST afferent innervation. Graded increases in shock intensity often recruited more than one ST afferent and ST-EPSCs had consistent threshold intensity, latency to onset, and unique EPSC waveforms that characterized each unitary ST afferent contact. The TRPV1 agonist capsaicin (100 nM) blocked the evoked TRPV1+ ST-EPSCs and defined them as either TRPV1+ or TRPV1- inputs. No partial responses to capsaicin were observed so that in NTS neurons that received one or multiple (2-5) direct ST afferent inputs--all were either blocked by capsaicin or were unaltered. Since TRPV1 mediates asynchronous release following TRPV1+ ST-evoked EPSCs, we likewise found that recruiting more than one ST afferent further augmented the asynchronous response and was eliminated by capsaicin. Thus, TRPV1+ and TRPV1- afferents are completely segregated to separate NTS neurons. As a result, the TRPV1 receptor augments glutamate release only within unmyelinated afferent pathways in caudal medial NTS and our work indicates a complete separation of C-type from A-type afferent information at these first central neurons.
- Published
- 2011
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42. Thermally active TRPV1 tonically drives central spontaneous glutamate release.
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Shoudai K, Peters JH, McDougall SJ, Fawley JA, and Andresen MC
- Subjects
- Action Potentials drug effects, Anilides pharmacology, Animals, Cadmium Compounds pharmacology, Calcium physiology, Capsaicin pharmacology, Cinnamates pharmacology, Excitatory Postsynaptic Potentials physiology, Male, Neurons, Afferent metabolism, Neurons, Afferent physiology, Rats, Rats, Sprague-Dawley, Signal Transduction drug effects, Signal Transduction physiology, Sodium Channel Blockers pharmacology, TRPV Cation Channels antagonists & inhibitors, Tetrodotoxin pharmacology, gamma-Aminobutyric Acid metabolism, Glutamic Acid metabolism, Synapses metabolism, TRPV Cation Channels physiology, Thermosensing physiology
- Abstract
Central synapses spontaneously release neurotransmitter at low rates. In the brainstem, cranial visceral afferent terminals in caudal solitary tract nucleus (NTS) display pronounced, activity-dependent, asynchronous release of glutamate and this extra release depends on TRPV1 receptors (TRPV1+). Asynchronous release is absent for afferents lacking TRPV1 (TRPV1-) and resting EPSC frequency was greater in TRPV1+. Here, we studied this basal activity difference by assessing thermal sensitivity of spontaneous and miniature synaptic events in TRPV1+ and TRPV1- second-order NTS neurons. The spontaneous EPSC rate decreased when temperature was decreased, increased steeply between 30 and 42°C only in TRPV1+ neurons, and was calcium-dependent. TRPV1-specific antagonist SB366791, but not TTX, strongly attenuated thermal responses. Temperature changes failed to alter EPSC frequency in TRPV1- neurons. EPSC amplitudes and decay kinetics changed little with temperature. IPSCs in these second-order NTS neurons were unaltered by temperature. Such results suggest that activated, presynaptic TRPV1+ receptors trigger continuous resting release of glutamate vesicles at physiological temperatures only in capsaicin-responsive terminals. In mechanically isolated individual neurons harvested from medial NTS, increases in temperature increased the rate of glutamate release only in TRPV1+ neurons, whereas IPSC rates were unaffected. Cadmium failed to block thermal increases in glutamate release, suggesting that calcium entry through TRPV1 channels may trigger glutamate release independently of voltage-activated calcium channels. Together, our findings indicate a new form of afferent signaling in which TRPV1 channels within central terminals of peripheral afferents tonically generate glutamate release in NTS at 37°C in the absence of afferent action potentials.
- Published
- 2010
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43. Primary afferent activation of thermosensitive TRPV1 triggers asynchronous glutamate release at central neurons.
- Author
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Peters JH, McDougall SJ, Fawley JA, Smith SM, and Andresen MC
- Subjects
- Afferent Pathways physiology, Anilides pharmacology, Animals, Capsaicin pharmacology, Cinnamates pharmacology, Electric Stimulation methods, Excitatory Postsynaptic Potentials drug effects, Excitatory Postsynaptic Potentials physiology, In Vitro Techniques, Male, Neurons classification, Neurons drug effects, Patch-Clamp Techniques methods, Rats, Rats, Sprague-Dawley, Sensory System Agents pharmacology, TRPV Cation Channels antagonists & inhibitors, Thermosensing drug effects, Thermosensing physiology, Glutamic Acid metabolism, Neurons metabolism, Solitary Nucleus cytology, TRPV Cation Channels metabolism
- Abstract
TRPV1 receptors feature prominently in nociception of spinal primary afferents but are also expressed in unmyelinated cranial visceral primary afferents linked to homeostatic regulation. Cranial visceral afferents enter the brain at the solitary tract nucleus (NTS) to control the heart, lungs, and other vital organs. Here we identify a role for central TRPV1 in the activity-dependent facilitation of glutamatergic transmission from solitary tract (ST) afferents. Fast, synchronous ST-NTS transmission from capsaicin-sensitive (TRPV1+) and -insensitive (TRPV1-) afferents was similar. However, afferent activation triggered long-lasting asynchronous glutamate release only from TRPV1+ synapses. Asynchronous release was proportional to synchronous EPSC amplitude, activity, and calcium entry. TRPV1 antagonists and low temperature blocked asynchronous release, but not evoked EPSCs. At physiological afferent frequencies, asynchronous release strongly potentiated the duration of postsynaptic spiking. This activity-dependent TPRV1-mediated facilitation is a form of synaptic plasticity that brings a unique central integrative feature to the CNS and autonomic regulation., (Copyright 2010 Elsevier Inc. All rights reserved.)
- Published
- 2010
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44. Parent-delivered compensatory education for children at risk of educational failure: Improving the academic and self-regulatory skills of a Sure Start preschool sample.
- Author
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Ford RM, McDougall SJ, and Evans D
- Subjects
- Attention, Child, Preschool, Curriculum, Female, Humans, Inhibition, Psychological, Male, Mathematical Concepts, Memory, Short-Term, Outcome and Process Assessment, Health Care, Personal Construct Theory, Reading, Socialization, Vocabulary, Wales, Writing, Early Intervention, Educational, Internal-External Control, Mothers psychology, Underachievement, Vulnerable Populations psychology
- Abstract
Thirty preschoolers from low-income families participated in a 12-month intervention programme, funded by Sure Start, which engaged them in scaffolded educational activities delivered at home by their mothers. Immediately following the programme, the intervention group outperformed matched controls in tests of academic knowledge, receptive vocabulary, and inhibitory control, but not short-term memory or theory of mind. Teachers' ratings of children's capabilities upon school entry favoured the intervention group, especially in terms of listening, responding, writing, mathematics, and personal/social skills. Superior inhibitory control, short-term memory, and numerical skills were associated with higher ratings whereas theory of mind made a unique, negative contribution to responding. We discuss the implications of these findings for efforts to nurture the development of cognitive self-regulation and school readiness during early childhood.
- Published
- 2009
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45. Convergence of cranial visceral afferents within the solitary tract nucleus.
- Author
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McDougall SJ, Peters JH, and Andresen MC
- Subjects
- Afferent Pathways physiology, Analysis of Variance, Animals, Biophysics, Brain Mapping, Electric Stimulation methods, Excitatory Postsynaptic Potentials physiology, In Vitro Techniques, Nerve Net physiology, Patch-Clamp Techniques, Rats, Rats, Sprague-Dawley, Reaction Time physiology, Synapses classification, Neurons, Afferent physiology, Solitary Nucleus cytology, Synapses physiology
- Abstract
Primary afferent axons within the solitary tract (ST) relay homeostatic information via glutamatergic synapses directly to second-order neurons within the nucleus of the solitary tract (NTS). These primary afferents arise from multiple organ systems and relay multiple sensory modalities. How this compact network organizes the flow of primary afferent information will shape central homeostatic control. To assess afferent convergence and divergence, we recorded ST-evoked synaptic responses in pairs of medial NTS neurons in horizontal brainstem slices. ST shocks activated EPSCs along monosynaptic or polysynaptic pathways. Gradations in shock intensity discriminated multiple inputs and stimulus recruitment profiles indicated that each EPSC was unitary. In 24 pairs, 75% were second-order neurons with 64% receiving one direct ST input with the remainder receiving additional convergent ST afferent inputs (22% two; 14% three monosynaptic ST-EPSCs). Some (34%) second-order neurons received polysynaptic EPSCs. Neurons receiving only higher-order inputs were uncommon (13%). Most ST-EPSCs were completely independent, but 4 EPSCs of a total of 81 had equal thresholds, highly correlated latencies, and synchronized synaptic failures consistent with divergence from a single source ST axon or from a common interneuron producing a pair of polysynaptic EPSCs. We conclude that ST afferent inputs are remarkably independent with little evidence of substantial shared information. Individual cells receive highly focused information from the viscera. Thus, afferent excitation of second-order NTS neurons is generally dominated by single visceral afferents and therefore focused on a single afferent modality and/or organ region.
- Published
- 2009
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46. Oxytocin enhances cranial visceral afferent synaptic transmission to the solitary tract nucleus.
- Author
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Peters JH, McDougall SJ, Kellett DO, Jordan D, Llewellyn-Smith IJ, and Andresen MC
- Subjects
- Analysis of Variance, Animals, Biotin analogs & derivatives, Biotin metabolism, Cranial Nerves drug effects, Dose-Response Relationship, Drug, Electric Stimulation methods, Excitatory Postsynaptic Potentials drug effects, Excitatory Postsynaptic Potentials physiology, Hormone Antagonists pharmacology, In Vitro Techniques, Male, Microscopy, Electron, Transmission methods, Neurons ultrastructure, Oxytocin analogs & derivatives, Patch-Clamp Techniques methods, Rats, Rats, Sprague-Dawley, Solitary Nucleus physiology, Synaptic Transmission physiology, Visceral Afferents drug effects, Cranial Nerves physiology, Neurons physiology, Oxytocin pharmacology, Solitary Nucleus cytology, Synaptic Transmission drug effects, Visceral Afferents physiology
- Abstract
Cranial visceral afferents travel via the solitary tract (ST) to contact neurons within the ST nucleus (NTS) and activate homeostatic reflexes. Hypothalamic projections from the paraventricular nucleus (PVN) release oxytocin (OT) to modulate visceral afferent communication with NTS neurons. However, the cellular mechanisms through which OT acts are poorly understood. Here, we electrophysiologically identified second-order NTS neurons in horizontal brainstem slices by their low-jitter, ST-evoked glutamatergic EPSCs. OT increased the frequency of miniature EPSCs in half of the NTS second-order neurons (13/24) but did not alter event kinetics or amplitudes. These actions were blocked by a selective OT receptor antagonist. OT increased the amplitude of ST-evoked EPSCs with no effect on event kinetics. Variance-mean analysis of ST-evoked EPSCs indicated OT selectively increased the release probability of glutamate from the ST afferent terminals. In OT-sensitive neurons, OT evoked an inward holding current and increased input resistance. The OT-sensitive current reversed at the K(+) equilibrium potential. In in vivo studies, NTS neurons excited by vagal cardiopulmonary afferents were juxtacellularly labeled with Neurobiotin and sections were stained to show filled neurons and OT-immunoreactive axons. Half of these physiologically characterized neurons (5/10) showed close appositions by OT fibers consistent with synaptic contacts. Electron microscopy of medial NTS found immunoreactive OT within synaptic boutons. Together, these findings suggest that OT released from PVN axons acts on a subset of second-order neurons within medial NTS to enhance visceral afferent transmission via presynaptic and postsynaptic mechanisms.
- Published
- 2008
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47. Paired assessment of volatile anesthetic concentrations with synaptic actions recorded in vitro.
- Author
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McDougall SJ, Peters JH, LaBrant L, Wang X, Koop DR, and Andresen MC
- Subjects
- Anesthetics, Inhalation analysis, Animals, Brain Stem chemistry, Brain Stem physiology, Gas Chromatography-Mass Spectrometry, Isoflurane analysis, Rats, Rats, Sprague-Dawley, Action Potentials drug effects, Anesthetics, Inhalation pharmacology, Isoflurane pharmacology, Synapses drug effects
- Abstract
The volatile anesthetic isoflurane poses a number of experimental challenges in the laboratory. Due to its rapid evaporation, the open conditions of most in vitro electrophysiological recording systems make the determination of actual isoflurane concentrations a challenge. Since the absolute anesthetic concentration in solution is directly related to efficacy, concentration measurements are important to allow comparisons between laboratory and clinical studies. In this study we quantify the sources of isoflurane loss during experimentation and describe a method for the measurement of isoflurane concentrations using gas chromatography and mass spectrometry simultaneous to in vitro electrophysiological measurements. Serial samples of perfused bath solution allowed correlation of isoflurane concentrations with ongoing biological effects. Saturated physiological solutions contained 13.4 +/- 0.2 mM isoflurane and were diluted to desired "nominal" concentrations for experiments. The perfusion system established stable isoflurane concentrations within the bath by 2 minutes. However, bath isoflurane concentrations varied substantially and unpredictably between experiments. The magnitudes of such discrepancies in isoflurane concentrations spanned clinically important levels. Our studies suggest that, despite countermeasures, solution handling significantly impacted the isoflurane content in the tissue bath. The magnitude of these discrepancies appears to necessitate systematic direct measurement of bath isoflurane concentrations during most in vitro conditions.
- Published
- 2008
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48. Isoflurane differentially modulates inhibitory and excitatory synaptic transmission to the solitary tract nucleus.
- Author
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Peters JH, McDougall SJ, Mendelowitz D, Koop DR, and Andresen MC
- Subjects
- Animals, Excitatory Postsynaptic Potentials physiology, Inhibitory Postsynaptic Potentials physiology, Male, Rats, Rats, Sprague-Dawley, Solitary Nucleus physiology, Synaptic Transmission physiology, Excitatory Postsynaptic Potentials drug effects, Inhibitory Postsynaptic Potentials drug effects, Isoflurane pharmacology, Solitary Nucleus drug effects, Synaptic Transmission drug effects
- Abstract
Background: Isoflurane anesthesia produces cardiovascular and respiratory depression, although the specific mechanisms are not fully understood. Cranial visceral afferents, which innervate the heart and lungs, synapse centrally onto neurons within the medial portion of the nucleus tractus solitarius (NTS). Isoflurane modulation of afferent to NTS synaptic communication may underlie compromised cardiorespiratory reflex function., Methods: Adult rat hindbrain slice preparations containing the solitary tract (ST) and NTS were used. Shocks to ST afferents evoked excitatory postsynaptic currents with low-variability (SEM <200 mus) latencies identifying neurons as second order. ST-evoked and miniature excitatory postsynaptic currents as well as miniature inhibitory postsynaptic currents were measured during isoflurane exposure. Perfusion bath samples were taken in each experiment to measure isoflurane concentrations by gas chromatography-mass spectrometry., Results: Isoflurane dose-dependently increased the decay-time constant of miniature inhibitory postsynaptic currents. At greater than 300 mum isoflurane, the amplitude of miniature inhibitory postsynaptic currents was decreased, but the frequency of events remained unaffected, whereas at equivalent isoflurane concentrations, the frequency of miniature excitatory postsynaptic currents was decreased. ST-evoked excitatory postsynaptic current amplitudes decreased without altering event kinetics. Isoflurane at greater than 300 mum increased the latency to onset and rate of synaptic failures of ST-evoked excitatory postsynaptic currents., Conclusions: In second-order NTS neurons, isoflurane enhances phasic inhibitory transmission via postsynaptic gamma-aminobutyric acid type A receptors while suppressing excitatory transmission through presynaptic mechanisms. These results suggest that isoflurane acts through multiple distinct mechanisms to inhibit neurotransmission within the NTS, which would underlie suppression of homeostatic reflexes.
- Published
- 2008
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49. Propofol enhances both tonic and phasic inhibitory currents in second-order neurons of the solitary tract nucleus (NTS).
- Author
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McDougall SJ, Bailey TW, Mendelowitz D, and Andresen MC
- Subjects
- 2-Amino-5-phosphonovalerate pharmacology, Animals, Dose-Response Relationship, Drug, Drug Interactions, Electric Stimulation methods, Excitatory Amino Acid Antagonists pharmacology, In Vitro Techniques, Neurons classification, Patch-Clamp Techniques methods, Quinoxalines pharmacology, Rats, Rats, Sprague-Dawley, Tetrodotoxin pharmacology, Anesthetics, Intravenous pharmacology, Inhibitory Postsynaptic Potentials drug effects, Neural Inhibition drug effects, Neurons drug effects, Propofol pharmacology, Solitary Nucleus cytology
- Abstract
The anesthetic propofol is thought to induce rapid hypnotic sedation by facilitating a GABAergic tonic current in forebrain neurons. The depression of cardiovascular and respiratory regulation often observed during propofol suggests potential additional actions within the brainstem. Here we determined the impacts of propofol on both GABAergic and glutamatergic synaptic mechanisms in a class of solitary tract nucleus (NTS) neurons common to brainstem reflex pathways. In horizontal brainstem slices, we recorded from NTS neurons directly activated by solitary tract (ST) axons. We identified these second-order NTS neurons by time-invariant ("jitter"<200 micros), "all-or-none" glutamatergic excitatory postsynaptic currents (EPSCs) in response to shocks to the ST. In order to assess propofol actions, we measured ST-evoked, spontaneous and miniature EPSCs and inhibitory postsynaptic currents (IPSCs) during propofol exposure. Propofol prolonged miniature IPSC decay time constants by 50% above control at 1.8 microM. Low concentrations of gabazine (SR-95531) blocked phasic GABA currents. At higher concentrations, propofol (30 microM) induced a gabazine-insensitive tonic current that was blocked by picrotoxin or bicuculline. In contrast, total propofol concentrations up to 30 microM had no effect on EPSCs. Thus, propofol enhanced phasic GABA events in NTS at lower concentrations than tonic current induction, opposite to the relative sensitivity observed in forebrain regions. These data suggest that therapeutic levels of propofol facilitate phasic (synaptic) inhibitory transmission in second-order NTS neurons which likely inhibits autonomic reflex pathways during anesthesia.
- Published
- 2008
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50. Icon identification in context: the changing role of icon characteristics with user experience.
- Author
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Isherwood SJ, McDougall SJ, and Curry MB
- Subjects
- Adult, Female, Humans, Male, Problem Solving, Psychomotor Performance, Reaction Time, Software, Time Factors, Communication, Mental Recall, Pattern Recognition, Visual, Symbolism
- Abstract
Objective: This research examined the relative importance of icon characteristics in determining the speed and accuracy of icon identification., Background: Studies to date have focused on the role of one or two icon characteristics when users first experience an icon set. This means that little is known about the relative importance of icon characteristics or how the role of icon characteristics might change as users gain experience with icons., Methods: Thirty participants carried out an icon identification task over a long series of trials to simulate learning through experience. Icon characteristics investigated included semantic distance, concreteness, familiarity, and visual complexity., Results: Icon characteristics were major determinants of performance, accounting for up to 69% of the variance observed in performance. However, the importance of icon characteristics changed with experience: Semantic distance is crucial initially while icon-function relationships are learned, but familiarity is important later because it has lasting effects on access to long-term memory representations., Conclusion: These findings suggest that icon concreteness may not be of primary importance when identifying icons and that semantic distance and familiarity may be more important., Application: Designers need to take into account icon characteristics other than concreteness when creating icons, particularly semantic distance and familiarity. The precise importance of the latter characteristics will vary depending on whether icons are rarely encountered or frequently used.
- Published
- 2007
- Full Text
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