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© 2015 The Authors.Neural stem cells in different locations of the postnatal mouse ventricular-subventricular zone (V-SVZ) generate different subtypes of olfactory bulb (OB) interneurons. High Sonic hedgehog (SHH) signaling in the ventral V-SVZ regulates t

The detection of mechanical qualities of foodstuffs is essential for nutrient acquisition, evaluation of food freshness, and bolus formation during mastication. However, the mechanisms through which mechanosensitive cells in the oral cavity transmit mechanical information from the periphery to the brain are not well defined. We hypothesized Merkel cells, which are epithelial mechanoreceptors and important for pressure and texture sensing in the skin, can be mechanically activated in the oral cavity. Using live-cell calcium imaging, we recorded Merkel cell activity in ex vivo gingival and palatal preparations from mice in response to mechanical stimulation. Merkel cells responded with distinct temporal patterns and activation thresholds in a region-specific manner, with Merkel cells in the hard palate having a higher mean activation threshold than those in the gingiva. Unexpectedly, we found that oral keratinocytes were also activated by mechanical stimulation, even in the absence of Merkel cells. This indicates that mechanical stimulation of oral mucosa independently activates at least two subpopulations of epithelial cells. Finally, we found that oral Merkel cells contribute to preference for consuming oily emulsion. To our knowledge, these data represent the first functional study of Merkel-cell physiology and its role in flavor detection in the oral cavity., (© 2024 The Authors. Physiological Reports published by Wiley Periodicals LLC on behalf of The Physiological Society and the American Physiological Society.)

Background: In early 2022, there was a sudden surge of patients infected by the Omicron variant of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) in Hong Kong (HK), resulting in 9,163 deaths as of 29 May 2022. Many of the local population had not been vaccinated before this wave. The number of patients who developed coronavirus disease 2019 (COVID-19) related respiratory failure outnumbered the capacity of intensive care unit (ICU) beds. Some of these patients had to be supported with high flow nasal cannula (HFNC) therapy outside ICU setting. HK was in crisis situation. The primary objective of this study is to assess the 28-day mortality of this group of patients. The secondary objective is to explore any predictors of non-survivors to help clinical decision-making in future crisis., Methods: This is a retrospective observational study of patients suffering from COVID-19 related respiratory failure who received HFNC therapy in general medical wards of two hospitals during the period of 17 Mar to 30 Apr 2022. Survival and risk factors were reviewed., Results: Forty-nine patients were recruited. Twenty-six patients (53%) survived at 28-day after initiation of HFNC support. Three clinical parameters were found to be significantly associated with mortality at 28-day: (I) SpO 2 /FiO 2 (SF) ratio <160 at 48 hours; (II) SF ratio <191 at 72 hours; (III) serial SF ratio at 48 or 72 hours showing no improvement over that at the time of initiation of HFNC therapy., Conclusions: Use of HFNC outside ICU setting showed benefit to patients suffering from COVID-19 related acute hypoxemic respiratory failure (AHRF). Serial SF ratio monitoring at 48 and 72 hours after therapy initiation might serve as predictors of outcome and thus guide clinical decision-making for medical resource allocation in outbreak situation., Competing Interests: Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://jtd.amegroups.com/article/view/10.21037/jtd-22-1507/coif). The authors have no conflicts of interest to declare., (2023 Journal of Thoracic Disease. All rights reserved.)

This study evaluates the association between antivirals (Molnupiravir and Nirmatrelvir-Ritonavir) and all-cause and respiratory mortality and organ dysfunction among high-risk COVID-19 patients during an Omicron outbreak. Two cohorts, Nirmatrelvir-Ritonavir versus control and Molnupiravir versus control, were constructed with inverse probability treatment weighting to balance baseline characteristics. Cox proportional hazards models evaluated the association of their use with all-cause mortality, respiratory mortality, and all-cause sepsis (a composite of circulatory shock, respiratory failure, acute liver injury, coagulopathy, and acute liver impairment). Patients recruited were hospitalized and diagnosed with the COVID-19 Omicron variant between February 22, 2022 and April 15, 2022, and followed up until May 15, 2022. The study included 17,704 patients. There were 4.67 and 22.7 total mortalities per 1000 person-days in the Nirmatrelvir-Ritonavir and control groups respectively before adjustment (weighted incidence rate ratio, - 18.1 [95% CI - 23.0 to - 13.2]; hazard ratio, 0.18 [95% CI, 0.11-0.29]). There were 6.64 and 25.9 total mortalities per 1000 person-days in the Molnupiravir and control groups respectively before adjustment (weighted incidence rate ratio per 1000 person-days, - 19.3 [95% CI - 22.6 to - 15.9]; hazard ratio, 0.23 [95% CI 0.18-0.30]). In all-cause sepsis, there were 13.7 and 35.4 organ dysfunction events per 1000 person-days in the Nirmatrelvir-Ritonavir and control groups respectively before adjustment (weighted incidence rate ratio per 1000 person-days, - 21.7 [95% CI - 26.3 to - 17.1]; hazard ratio, 0.44 [95% CI 0.38-0.52]). There were 23.7 and 40.8 organ dysfunction events in the Molnupiravir and control groups respectively before adjustment (weighted incidence ratio per 1000 person-days, - 17.1 [95% CI, - 20.6 to - 13.6]; hazard ratio, 0.63 [95% CI 0.58-0.69]). Among COVID-19 hospitalized patients, use of either Nirmatrelvir-Ritonavir or Molnupiravir compared with no antiviral use was associated with a significantly lower incidence of 28-days all-cause and respiratory mortality and sepsis., (© 2023. The Author(s).)

Background: Real-world data is currently limited on the association between oral antiviral therapy and healthcare system burden in patients with mild-to-moderate COVID-19. This study aims to evaluate the clinical and cost effectiveness of Molnupiravir and Nirmatrelvir-ritonavir use in reducing mortality in this population., Methods: This is a retrospective cohort study involving 54,355 COVID-19 patients during February 22-March 31,2022 in Hong Kong. Inverse probability of treatment weighting (IPTW) was used to adjust patient characteristics. Our exposure of interest was Molnupiravir/Nirmatrelvir-Ritonavir prescription, with all-cause mortality as the primary outcome. IPTW-adjusted multivariate regressions were used to estimate treatment impact on clinic re-attendance and unplanned admissions. Finally, attributed cost and incremental cost-effectiveness ratios (ICER) were estimated., Findings: In the outpatient cohort ( N = 33,217, 61.1%), 16.1% used Molnupiravir and 13.4% used Nirmatrelvir-Ritonavir, while in the inpatient cohort ( N = 21,138, 38.9%), 3.8% used Molnupiravir and 1.3% used Nirmatrelvir-Ritonavir. IPTW-adjusted Cox model estimated that Molnupiravir (hazard ratio (HR)(95%CI)=0.31 (0.24-0.40), P< 0.0001) and Nirmatrelvir-Ritonavir (HR=0.10 (95%CI 0.05-0.21), P< 0.0001) were significantly associated with a reduced mortality hazard. In the outpatient cohort, both antiviral prescriptions were associated with reduced odds for unplanned hospital admissions (Molnupiravir: odds ratio (OR) =0.72 (0.52-0.98), P=0.039; Nirmatrelvir-Ritonavir: OR=0.37 (0.23-0.60), P< 0.0001). Among hospitalised patients, both antiviral prescriptions were associated with significant reductions in the odds ratios for 28-days readmission (Molnupiravir: OR=0.71 (0.52-0.97), P= 0.031; Nirmatrelvir-Ritonavir: OR=0.47 (0.24-0.93), P= 0.030). ICERs for death averted for Molnupiravir stood at USD493,345.09 in outpatient settings and USD2,629.08 in inpatient settings. In outpatient settings, Nirmatrelvir-ritonavir cost USD331,105.27 to avert one death, but saved USD5,502.53 to avert one death in comparison with standard care., Interpretation: In high-risk patients in Hong Kong with mild-to-moderate COVID-19, Molnupiravir and Nirmatrelvir-Ritonavir prescriptions were associated with reduced all-cause mortality and significant cost savings., Funding: Centre for Health Systems & Policy Research is funded by The Tung's Foundation; and The Laboratory of Data Discovery for Health Limited(D24H) is funded the AIR@InnoHK platform administered by the Innovation and Technology Commission of Hong Kong. Funders did not have any role in study design, data collection, data analysis, interpretation and writing of this manuscript., Competing Interests: No conflict of interest existed for AKCW, SCLC, TTLL, OWKT, KWYC, SL, CKT, TY, THR. CYC, AWLC, KW, ELYW of Centre for Health Systems & Policy Research are supported by funding from The Tung's Foundation. LYFL, ETFY, JWKH of The Laboratory of Data Discovery for Health Limited (D24H) are supported by funding from the AIR@InnoHK platform administered by the Innovation and Technology Commission of Hong Kong., (© 2022 The Authors.)

Optogenetics has revolutionized the capability of controlling genetically modified neurons in vitro and in vivo and has become an indispensable neuroscience tool. Using light as a probe for selective neuronal activation or inhibition and as a means to read out neural activity has dramatically enhanced our understanding of complex neural circuits. However, a common limitation of optogenetic studies to date is their invasiveness and spatiotemporal range. Direct viral injections into the brain tissue along with implantation of optical fibers and recording electrodes can disrupt the neuronal circuitry and cause significant damage. Conventional approaches are spatially limited around the site of the direct injection and insufficient in examining large networks throughout the brain. Lastly, optogenetics is currently not easily scalable to large animals or humans. Here, we demonstrate that optogenetic excitation can be achieved entirely non-invasively through the intact skull in mice. Using a needle-free combination of focused ultrasound-mediated viral delivery and extracorporeal illumination with red light, we achieved selective neuronal activation at depths up to 4 mm in the murine brain, confirmed through cFos expression and electrophysiology measurements within the treated areas. Ultrasound treatment significantly reduced freezing time during recall in fear conditioning experiments, but remote light exposure had a moderate effect on the freezing behavior of mice treated with viral vectors. The proposed method has the potential to open new avenues of studying, but also stimulating, neuronal networks, in an effort to elucidate normal or dysfunctional brain activity and treat neurological diseases. Finally, the same non-invasive methodology could be combined with gene therapy and applied to other organs, such as the eye and the heart., Competing Interests: Declaration of competing interest The authors declare no competing financial interests., (Copyright © 2022 The Authors. Published by Elsevier Inc. All rights reserved.)

Neurons of the peripheral nervous system (PNS) are tasked with diverse roles, from encoding touch, pain, and itch to interoceptive control of inflammation and organ physiology. Thus, technologies that allow precise control of peripheral nerve activity have the potential to regulate a wide range of biological processes. Noninvasive modulation of neuronal activity is an important translational application of focused ultrasound (FUS). Recent studies have identified effective strategies to modulate brain circuits; however, reliable parameters to control the activity of the PNS are lacking. To develop robust noninvasive technologies for peripheral nerve modulation, we employed targeted FUS stimulation and electrophysiology in mouse ex vivo skin-saphenous nerve preparations to record the activity of individual mechanosensory neurons. Parameter space exploration showed that stimulating neuronal receptive fields with high-intensity, millisecond FUS pulses reliably and repeatedly evoked one-to-one action potentials in all peripheral neurons recorded. Interestingly, when neurons were classified based on neurophysiological properties, we identified a discrete range of FUS parameters capable of exciting all neuronal classes, including myelinated A fibers and unmyelinated C fibers. Peripheral neurons were excited by FUS stimulation targeted to either cutaneous receptive fields or peripheral nerves, a key finding that increases the therapeutic range of FUS-based peripheral neuromodulation. FUS elicited action potentials with millisecond latencies compared with electrical stimulation, suggesting ion channel–mediated mechanisms. Indeed, FUS thresholds were elevated in neurons lacking the mechanically gated channel PIEZO2. Together, these results demonstrate that transcutaneous FUS drives peripheral nerve activity by engaging intrinsic mechanotransduction mechanisms in neurons [B. U. Hoffman, PhD thesis, (2019)].

Neuropathic pain caused by lesions to somatosensory neurons due to injury or disease is a widespread public health problem that is inadequately managed by small-molecule therapeutics due to incomplete pain relief and devastating side effects. Genetically encoded molecules capable of interrupting nociception have the potential to confer long-lasting analgesia with minimal off-target effects. Here, we utilize a targeted ubiquitination approach to achieve a unique posttranslational functional knockdown of high-voltage-activated calcium channels (HVACCs) that are obligatory for neurotransmission in dorsal root ganglion (DRG) neurons. CaV-aβlator comprises a nanobody targeted to CaV channel cytosolic auxiliary β subunits fused to the catalytic HECT domain of the Nedd4-2 E3 ubiquitin ligase. Subcutaneous injection of adeno-associated virus serotype 9 encoding CaV-aβlator in the hind paw of mice resulted in the expression of the protein in a subset of DRG neurons that displayed a concomitant ablation of CaV currents and also led to an increase in the frequency of spontaneous inhibitory postsynaptic currents in the dorsal horn of the spinal cord. Mice subjected to spare nerve injury displayed a characteristic long-lasting mechanical, thermal, and cold hyperalgesia underlain by a dramatic increase in coordinated phasic firing of DRG neurons as reported by in vivo Ca2+ spike recordings. CaV-aβlator significantly dampened the integrated Ca2+ spike activity and the hyperalgesia in response to nerve injury. The results advance the principle of targeting HVACCs as a gene therapy for neuropathic pain and demonstrate the therapeutic potential of posttranslational functional knockdown of ion channels achieved by exploiting the ubiquitin-proteasome system.

Atopic dermatitis (AD), driven by interleukins (IL-4/IL-13), is a chronic inflammatory skin disease characterized by intensive pruritus. However, it is unclear how immune signaling and sensory response pathways cross talk with each other. We differentiated itch sensory neuron-like cells (ISNLCs) from iPSC lines. These ISNLCs displayed neural markers and action potentials and responded specifically to itch-specific stimuli. These ISNLCs expressed receptors specific for IL-4/IL-13 and were activated directly by the two cytokines. We successfully innervated these ISNLCs into full thickness human skin constructs. These innervated skin grafts can be used in clinical applications such as wound healing. Moreover, the availability of such innervated skin models will be valuable to develop drugs to treat skin diseases such as AD., (© 2021 The Authors. Bioengineering & Translational Medicine published by Wiley Periodicals LLC on behalf of American Institute of Chemical Engineers.)

This study explores the theoretical proposal that developmental dyslexia involves a failure to develop perceptual expertise with words despite adequate education. Among a group of Hong Kong Chinese children diagnosed with developmental dyslexia, we investigated the relationship between Chinese word reading and perceptual expertise with Chinese characters. In a perceptual fluency task, the time of visual exposure to Chinese characters was manipulated and limited such that the speed of discrimination of a short sequence of Chinese characters at an accuracy level of 80% was estimated. Pair-wise correlations showed that perceptual fluency for characters predicted speeded and non-speeded word reading performance. Exploratory hierarchical regressions showed that perceptual fluency for characters accounted for 5.3% and 9.6% variance in speeded and non-speeded reading respectively, in addition to age, non-verbal IQ, phonological awareness, morphological awareness, rapid automatized naming (RAN) and perceptual fluency for digits. The findings suggest that perceptual expertise with words plays an important role in Chinese reading performance in developmental dyslexia, and that perceptual training is a potential remediation direction., Competing Interests: The authors have declared that no competing interests exist.

Objective: Use next-generation sequencing (NGS) technology to improve our diagnostic yield in patients with suspected genetic disorders in the Asian setting., Design: A diagnostic study conducted between 2014 and 2019 (and ongoing) under the Singapore Undiagnosed Disease Program. Date of last analysis was 1 July 2019., Setting: Inpatient and outpatient genetics service at two large academic centres in Singapore., Patients: Inclusion criteria: patients suspected of genetic disorders, based on abnormal antenatal ultrasound, multiple congenital anomalies and developmental delay., Exclusion Criteria: patients with known genetic disorders, either after clinical assessment or investigations (such as karyotype or chromosomal microarray)., Interventions: Use of NGS technology-whole exome sequencing (WES) or whole genome sequencing (WGS)., Main Outcome Measures: (1) Diagnostic yield by sequencing type, (2) diagnostic yield by phenotypical categories, (3) reduction in time to diagnosis and (4) change in clinical outcomes and management., Results: We demonstrate a 37.8% diagnostic yield for WES (n=172) and a 33.3% yield for WGS (n=24). The yield was higher when sequencing was conducted on trios (40.2%), as well as for certain phenotypes (neuromuscular, 54%, and skeletal dysplasia, 50%). In addition to aiding genetic counselling in 100% of the families, a positive result led to a change in treatment in 27% of patients., Conclusion: Genomic sequencing is an effective method for diagnosing rare disease or previous 'undiagnosed' disease. The clinical utility of WES/WGS is seen in the shortened time to diagnosis and the discovery of novel variants. Additionally, reaching a diagnosis significantly impacts families and leads to alteration in management of these patients., Competing Interests: Competing interests: None declared., (© Author(s) (or their employer(s)) 2021. No commercial re-use. See rights and permissions. Published by BMJ.)

A 41-year-old man from the emergency department presented with fever for 2 weeks, sore throat, dry cough and generalized umbilicated skin lesions (face (Fig. 1), and chest (Fig. 2)). HIV antibody was positive, CD4+ count was 2/μL. His skin swab, sputum and blood culture all yielded Talaromyces ( Penicillium ) marneffei (Fig. 3). Talaromyces marneffei is an important cause of morbidity and mortality in HIV-infected and other immunosuppressed patients who live in or are from endemic areas especially Southeast Asia. Amphotericin B or Itraconazole should be initiated as soon as possible for patients with talaromycosis.

Peripheral nerve lesions provoke apoptosis in the dorsal horn of the spinal cord. The cause of cell death, the involvement of neurons, and the relevance for the processing of somatosensory information are controversial. Here, we demonstrate in a mouse model of sciatic nerve injury that glutamate-induced neurodegeneration and loss of γ-aminobutyric acid (GABA)ergic interneurons in the superficial dorsal horn promote the transition from acute to chronic neuropathic pain. Conditional deletion of Grin1, the essential subunit of N-methyl-d-aspartate-type glutamate receptors (NMDARs), protects dorsal horn neurons from excitotoxicity and preserves GABAergic inhibition. Mice deficient in functional NMDARs exhibit normal nociceptive responses and acute pain after nerve injury, but this initial increase in pain sensitivity is reversible. Eliminating NMDARs fully prevents persistent pain-like behavior. Reduced pain in mice lacking proapoptotic Bax confirmed the significance of neurodegeneration. We conclude that NMDAR-mediated neuron death contributes to the development of chronic neuropathic pain., (Copyright © 2018 The Authors. Published by Elsevier Inc. All rights reserved.)

The superficial dorsal horn is the synaptic termination site for many peripheral sensory fibers of the somatosensory system. A wide range of sensory modalities are represented by these fibers, including pain, itch, and temperature. Because the involvement of local inhibition in the dorsal horn, specifically that mediated by the inhibitory amino acids GABA and glycine, is so important in signal processing, we investigated regional inhibitory control of excitatory interneurons under control conditions and peripheral inflammation-induced mechanical allodynia. We found that excitatory interneurons and projection neurons in lamina I and IIo are dominantly inhibited by GABA while those in lamina IIi and III are dominantly inhibited by glycine. This was true of identified neuronal subpopulations: neurokinin 1 receptor-expressing (NK1R+) neurons in lamina I were GABA-dominant while protein kinase C gamma-expressing (PKCγ+) neurons at the lamina IIi-III border were glycine-dominant. We found this pattern of synaptic inhibition to be consistent with the distribution of GABAergic and glycinergic neurons identified by immunohistochemistry. Following complete Freund's adjuvant injection into mouse hindpaw, the frequency of spontaneous excitatory synaptic activity increased and inhibitory synaptic activity decreased. Surprisingly, these changes were accompanied by an increase in GABA dominance in lamina IIi. Because this shift in inhibitory dominance was not accompanied by a change in the number of inhibitory synapses or the overall postsynaptic expression of glycine receptor α1 subunits, we propose that the dominance shift is due to glycine receptor modulation and the depressed function of glycine receptors is partially compensated by GABAergic inhibition. SIGNIFICANCE STATEMENT Pain associated with inflammation is a sensation we would all like to minimize. Persistent inflammation leads to cellular and molecular changes in the spinal cord dorsal horn, including diminished inhibition, which may be responsible for enhance excitability. Investigating inhibition in the dorsal horn following peripheral inflammation is essential for development of improved ways to control the associated pain. In this study, we have elucidated regional differences in inhibition of excitatory interneurons in mouse dorsal horn. We have also discovered that the dominating inhibitory neurotransmission within specific regions of dorsal horn switches following peripheral inflammation and the accompanying hypersensitivity to thermal and mechanical stimuli. Our novel findings contribute to a more complete understanding of inflammatory pain., (Copyright © 2017 the authors 0270-6474/17/372337-13$15.00/0.)

Background Aims: Mesenchymal stromal cells (MSCs) have been identified as pan-immunosuppressant in various in vitro and in vivo inflammatory models. Although the immunosuppressive activity of MSCs has been explored in various contexts, the precise molecular signaling pathways that govern inhibitory functions remain poorly elucidated., Methods: By using a microarray-based global gene expression profiling system, this study aimed to decipher the underlying molecular pathways that may mediate the immunosuppressive activity of umbilical cord-derived MSCs (UC-MSCs) on activated T cells., Results: In the presence of UC-MSCs, the proliferation of activated T cells was suppressed in a dose-depended manner by cell-to-cell contact mode via an active cell-cycle arrest at the G0/G1 phase of the cell cycle. The microarray analysis revealed that particularly, IFNG, CXCL9, IL2, IL2RA and CCND3 genes were down-regulated, whereas IL11, VSIG4, GFA1, TIMP3 and BBC3 genes were up-regulated by UC-MSCs. The dysregulated gene clusters associated with immune-response-related ontologies, namely, lymphocyte proliferation or activation, apoptosis and cell cycle, were further analyzed., Conclusions: Among the nine canonical pathways identified, three pathways (namely T-helper cell differentiation, cyclins and cell cycle regulation, and gap/tight junction signalling pathways) were highly enriched with these dysregulated genes. The pathways represent putative molecular pathways through which UC-MSCs elicit immunosuppressive activity toward activated T cells. This study provides a global snapshot of gene networks and pathways that contribute to the ability of UC-MSCs to suppress activated T cells., (Copyright © 2016 International Society for Cellular Therapy. Published by Elsevier Inc. All rights reserved.)

Microglia begin colonizing the developing brain as early as embryonic day 9, prior to the emergence of neurons and other glia. Their ontogeny is also distinct from other central nervous system cells, as they derive from yolk sac hematopoietic progenitors and not neural progenitors. In this review, we feature these unique characteristics of microglia and assess the spatiotemporal similarities between microglia colonization of the central nervous system and embryonic neurogenesis. We also infer to existing evidence for microglia function from embryonic through to postnatal neurodevelopment to postulate roles for microglia in neurogenesis., (© 2016 by the Society for Experimental Biology and Medicine.)

Microglia are resident macrophages of the central nervous system (CNS). Apart from playing vital roles as sentinel cells, they are crucial in physiological processes such as synaptic pruning during brain development. CNS disorders require an understanding of the contribution of each cellular compartment to the pathogenesis. Elucidating the role of microglia in disease development and progression in the intricate CNS environment is technically challenging and requires the establishment of reliable, reproducible techniques to isolate and culture microglia. A number of different protocols have been developed for isolation of neonatal microglia and here we compare two widely used methods, namely, mild trypsinization and EasySep® magnetic separation. EasySep® magnetic separation provided higher microglia yield, and flow cytometric evaluation of CD11b and F4/80 markers revealed that EasySep® separation method also produced significantly higher purity compared to mild trypsinization. Microglia isolated using EasySep® separation method were functional, as demonstrated by the generation of nitric oxide, IL-6, TNF-α, and MCP-1 in response to lipopolysaccharide stimulation. In summary, this study has revealed that magnetic separation is superior to mild trypsinization in terms of yield and purity of microglia., (© 2015 International Federation for Cell Biology.)

Neural stem cells in different locations of the postnatal mouse ventricular-subventricular zone (V-SVZ) generate different subtypes of olfactory bulb (OB) interneurons. High Sonic hedgehog (SHH) signaling in the ventral V-SVZ regulates the production of specific subtypes of neurons destined for the OB. Here we found a transient territory of high SHH signaling in the dorsal V-SVZ beneath the corpus callosum (CC). Using intersectional lineage tracing in neonates to label dorsal radial glial cells (RGCs) expressing the SHH target gene Gli1, we demonstrate that this region produces many CC cells in the oligodendroglial lineage and specific subtypes of neurons in the OB. The number of oligodendroglial cells generated correlated with the levels of SHH signaling. This work identifies a dorsal domain of SHH signaling, which is an important source of oligodendroglial cells for the postnatal mammalian forebrain., (Copyright © 2015 The Authors. Published by Elsevier Inc. All rights reserved.)

The apical domain of embryonic (radial glia) and adult (B1 cells) neural stem cells (NSCs) contains a primary cilium. This organelle has been suggested to function as an antenna for the detection of morphogens or growth factors. In particular, primary cilia are essential for Hedgehog (Hh) signaling, which plays key roles in brain development. Their unique location facing the ventricular lumen suggests that primary cilia in NSCs could play an important role in reception of signals within the cerebrospinal fluid. Surprisingly, ablation of primary cilia using conditional alleles for genes essential for intraflagellar transport [kinesin family member 3A (Kif3a) and intraflagellar transport 88 (Ift88)] and Cre drivers that are activated at early [Nestin; embryonic day 10.5 (E10.5)] and late [human glial fibrillary acidic protein (hGFAP); E13.5] stages of mouse neural development resulted in no apparent developmental defects. Neurogenesis in the ventricular-subventricular zone (V-SVZ) shortly after birth was also largely unaffected, except for a restricted ventral domain previously known to be regulated by Hh signaling. However, Kif3a and Ift88 genetic ablation also disrupts ependymal cilia, resulting in hydrocephalus by postnatal day 4. To directly study the role of B1 cells' primary cilia without the confounding effects of hydrocephalus, we stereotaxically targeted elimination of Kif3a from a subpopulation of radial glia, which resulted in ablation of primary cilia in a subset of B1 cells. Again, this experiment resulted in decreased neurogenesis only in the ventral V-SVZ. Primary cilia ablation led to disruption of Hh signaling in this subdomain. We conclude that primary cilia are required in a specific Hh-regulated subregion of the postnatal V-SVZ.

NMDA receptors are important elements in pain signaling in the spinal cord dorsal horn. They are heterotetramers, typically composed of two GluN1 and two of four GluN2 subunits: GluN2A-2D. Mice lacking some of the GluN2 subunits show deficits in pain transmission yet functional synaptic localization of these receptor subtypes in the dorsal horn has not been fully resolved. In this study, we have investigated the composition of synaptic NMDA receptors expressed in monosynaptic and polysynaptic pathways from peripheral sensory fibers to lamina I neurons in rats. We focused on substance P receptor-expressing (NK1R+) projection neurons, critical for expression of hyperalgesia and allodynia. EAB-318 and (R)-CPP, GluN2A/B antagonists, blocked both monosynaptic and polysynaptic NMDA EPSCs initiated by primary afferent activation by ∼90%. Physiological measurements exploiting the voltage dependence of monosynaptic EPSCs similarly indicated dominant expression of GluN2A/B types of synaptic NMDA receptors. In addition, at synapses between C fibers and NK1R+ neurons, NMDA receptor activation initiated a secondary, depolarizing current. Ifenprodil, a GluN2B antagonist, caused modest suppression of monosynaptic NMDA EPSC amplitudes, but had a widely variable, sometimes powerful, effect on polysynaptic responses following primary afferent stimulation when inhibitory inputs were blocked to mimic neuropathic pain. We conclude that GluN2B subunits are moderately expressed at primary afferent synapses on lamina I NK1R+ neurons, but play more important roles for polysynaptic NMDA EPSCs driven by primary afferents following disinhibition, supporting the view that the analgesic effect of the GluN2B antagonist on neuropathic pain is at least in part, within the spinal cord., (Copyright © 2014 the authors 0270-6474/14/3410808-13$15.00/0.)

Background: We report a novel method of culturing microglia in three dimension (3D) using collagen as a substrate. By culturing microglia within a matrix, we aim to emulate the physical state of microglia embedded within parenchyma., Methods: BV2 microglia cell suspensions were prepared with type I collagen and cast into culture plates. To characterise the BV2 microglia cultured in 3D, the cultures were evaluated for their viability, cell morphology and response to lipopolysaccharide (LPS) activation. Conventional monolayer cultures (grown on uncoated and collagen-coated polystyrene) were set up concurrently for comparison., Results: BV2 microglia in 3D collagen matrices were viable at 48 hrs of culture and exhibit a ramified morphology with multiplanar cytoplasmic projections. Following stimulation with 1 μg/ml LPS, microglia cultured in 3D collagen gels increase their expression of nitric oxide (NO) and CD40, indicating their capacity to become activated within the matrix. Up to 97.8% of BV2 microglia grown in 3D cultures gained CD40 positivity in response to LPS, compared to approximately 60% of cells grown in a monolayer (P<.05). BV2 microglia in 3D collagen gels also showed increased mRNA and protein expression of inflammatory cytokines IL-6, TNF-α and the chemoattractant MCP-1 following LPS stimulation., Conclusions: In summary, BV2 microglia cultured in 3D collagen hydrogels exhibit multiplanar cytoplasmic projections and undergo a characteristic and robust activation response to LPS. This culture system is accessible to a wide range of analyses and provides a useful new in vitro tool for research into microglial activation.

Neural stem cells (NSCs) in the walls of the lateral ventricles continue to produce new neurons and oligodendrocytes throughout life. The identification of NSCs, long-range neuronal migration, and the integration of new neurons into fully formed mature neural circuits-all in the juvenile or adult brain-has dramatically changed concepts in neurodevelopment and suggests new strategies for brain repair. Yet, the latter has to be seen in perspective: NSCs in the adult are heterogeneous and highly regionally specified; young neurons derived from these primary progenitors migrate and integrate in specific brain regions. Neurogenesis appears to have a function in brain plasticity rather than brain repair. If similar processes could be induced in regions of the brain that are normally not a target of new neurons, therapeutic neuronal replacement may one day reinstate neural circuit plasticity and possibly repair broken neural circuits.

In the walls of the lateral ventricles of the adult mammalian brain, neural stem cells (NSCs) and ependymal (E1) cells share the apical surface of the ventricular-subventricular zone (V-SVZ). In a recent article, we show that supraependymal serotonergic (5HT) axons originating from the raphe nuclei in mice form an extensive plexus on the walls of the lateral ventricles where they contact E1 cells and NSCs. Here we further characterize the contacts between 5HT supraependymal axons and E1 cells in mice, and show that suprependymal axons tightly associated to E1 cells are also present in the walls of the human lateral ventricles. These observations raise interesting questions about the function of supraependymal axons in the regulation of E1 cells.

Sensory information transmitted to the spinal cord dorsal horn is modulated by a complex network of excitatory and inhibitory interneurons. The two main inhibitory transmitters, GABA and glycine, control the flow of sensory information mainly by regulating the excitability of dorsal horn neurons. A presynaptic action of GABA has also been proposed as an important modulatory mechanism of transmitter release from sensory primary afferent terminals. By inhibiting the release of glutamate from primary afferent terminals, activation of presynaptic GABA receptors could play an important role in nociceptive and tactile sensory coding, while changes in their expression or function could be involved in pathological pain conditions, such as allodynia., (© 2013 New York Academy of Sciences.)

Introduction: Cavum velum interpositum (CVI) is commonly an incidental asymptomatic finding on imaging studies. Encystment can occur and, in most situations, is also asymptomatic. Clinical symptoms occurring in patients with CVI cysts have been reported infrequently with the result that the relationship of these symptoms and the cyst are usually unclear. This report contributes to the knowledge base of symptoms that can occur in patients with CVI and the response of symptoms to effective treatment., Patients and Methods: We report the clinical outcomes of a 3-year-old male patient and a 13-year-old female patient with symptoms and CVI cysts on imaging who were treated successfully with endoscopic fenestration., Results: The developmental delay and occasional headache present in the 3-year-old male patient resolved after endoscopic fenestration; however, the 13-year-old patient who had neuropsychiatric symptoms did not improve., Conclusions: Our cases add to the literature describing the response to cyst treatment in symptomatic patients harboring CVI cysts. Symptoms due to CSF pathway obstruction may respond to cyst fenestration, while the response of symptoms in patents who do not have clear CSF circulation disorders is less predictable.

OBJECTIVE. A significant number of critically ill mechanically ventilated patients are not admitted to the Intensive Care Unit but are cared for on general wards. This study looked at the outcome of these patients. DESIGN. Case series. SETTING. A 1100-bed tertiary hospital in Hong Kong. PATIENTS. All adult patients admitted in a 2.5-year period who received invasive mechanical ventilation on general medical wards without admission to Intensive Care Unit or other special care areas. INTERVENTIONS. Invasive mechanical ventilation. MAIN OUTCOME MEASURES. The observed number of deaths, the expected number of deaths as derived from the Mortality Probability Model II system admission model, and other morbidity measures. RESULTS. Among 755 patients studied, the observed number of deaths was 673, which amounts to a mortality of 89.1%. The expected number of deaths was 570. The risk-standardised mortality ratio was 1.18 (95% confidence interval, 1.09-1.28; P<0.0005). Patients with chronic obstructive pulmonary disease had the lowest mortality rate of 70.8% (P<0.005). The post-cardiac arrest subgroup had the highest mortality of 99.0%. CONCLUSIONS. There was a worse-than-predicted survival in the absence of Intensive Care Unit care for the critically ill patients who received mechanical ventilation on general wards. Patients with chronic obstructive pulmonary disease warranted more Intensive Care Unit admissions. Early discontinuation of invasive support should be seriously considered in the post-cardiac arrest patients.

Morquio syndrome, or mucopolysaccharidosis type IV, is a rare enzyme deficiency disorder and results in skeletal dysplasia. Odontoid dysplasia is common among affected patients, resulting in atlantoaxial instability and spinal cord compression. Surgical treatments include decompression and prophylactic fusion, during which intraoperative neuromonitoring is important to alert the surgical team to changes in cord function so that they can prevent or mitigate spinal cord injury. This report describes a 16-year-old girl with Morquio syndrome who developed paraplegia due to thoracic spinal cord infarction during foramen magnum and atlantal decompression. This tragic event demonstrates the following: 1) that patients with Morquio syndrome are at risk for ischemic spinal cord injury at levels remote from areas of maximal anatomical compression while under anesthesia in the prone position, possibly due to impaired cardiac output; 2) the significance of absent motor evoked potential responses in the lower limbs with preserved upper-limb responses in an ambulatory patient; 3) the importance of establishing intraoperative neuromonitoring baseline assessments prior to turning patients to the prone position following induction of anesthesia; and 4) the importance of monitoring cardiac output during prone positioning in patients with chest wall deformity.

Background: Mesenchymal stem cells (MSC) have great potential in regenerative medicine, immunotherapy and gene therapy due to their unique properties of self-renewal, high plasticity, immune modulation and ease for genetic modification. However, production of MSC at sufficient clinical scale remains an issue as in vitro generation of MSC inadequately fulfils the demand with respect to patients., Objectives: This study has aimed to establish optimum conditions to generate and characterize MSC from human umbilical cord (UC-MSC)., Materials and Methods: To optimize MSC population growth, basic fibroblast growth factor (bFGF) was utilized in culture media. Effects of bFGF on expansion kinetics, cell cycle, survival of UC-MSC, cytokine secretion, expression of early stem-cell markers and immunomodulation were investigated., Results: bFGF supplementation profoundly enhanced UC-MSC proliferation by reducing population doubling time without altering immunophenotype and immunomodulatory function of UC-MSC. However, cell cycle studies revealed that bFGF drove the cells into the cell cycle, as a higher proportion of cells resided in S phase and progressed into M phase. Consistent with this, bFGF was shown to promote expression of cyclin D proteins and their relevant kinases to drive UC-MSC to transverse cell cycle check points, thus, committing the cells to DNA synthesis. Furthermore, supplementation with bFGF changed the cytokine profiles of the cells and reduced their apoptotic level., Conclusion: Our study showed that bFGF supplementation of UC-MSC culture enhanced the cells' growth kinetics without compromising their nature., (© 2012 Blackwell Publishing Ltd.)

MSCs (mesenchymal stem cells) promise a great potential for regenerative medicine due to their unique properties of self-renewal, high plasticity, modulation of immune response and the flexibility for genetic modification. Therefore, the increasing demand for cellular therapy necessitates a larger-scale production of MSC; however, the technical and ethical issues had put a halt on it. To date, studies have shown that MSC could be derived from human UC (umbilical cord), which is once considered as clinical waste. We have compared the two conventional methods which are classic enzymatic digestion and explant method with our newly tailored enzymatic-mechanical disassociation method to generate UC-MSC. The generated UC-MSCs from the methods above were characterized based on their immunophenotyping, early embryonic transcription factors expression and mesodermal differentiation ability. Our results show that enzymatic-mechanical disassociation method increase the initial nucleated cell yield greatly (approximately 160-fold) and maximized the successful rate of UC-MSC generation. Enzymatic-mechanical disassociation-derived UC-MSC exhibited fibroblastic morphology and surface markers expression of CD105, CD73, CD29, CD90 and MHC class I. Furthermore, these cells constitutively express early embryonic transcription factors (Nanog, Oct-4, Sox-2 and Rex-1), as confirmed by RT-PCR, indicating their multipotency and high self-renewal capacity. They are also capable of differentiating into osteoblasts and adipocytes when given an appropriate induction. The present study demonstrates a new and efficient approach in generating MSC from UC, hence serving as ideal alternative source of mesenchymal stem cell for clinical and research use.

The immunomodulatory activity of Cassia auriculata (CA)-derived polyphenols was tested on aged rats. Rats (24-26 months old) were given CA polyphenols supplementation at doses of 25, 50, and 100 mg/kg for 28 days. Flow cytometry analysis of CA polyphenols-treated aged rats showed increased T and B cells percentage along with enhanced proliferation of splenocytes in both resting and LPS-stimulated cells. Increased percentage of pan T cells is further supported by an elevation of CD4+, CD8+, and CD4+CD25+ regulatory cells. In terms of innate immune cell activity, CA polyphenol supplementation reduced the oxidative burst activity of neutrophils in response to PMA and Escherichia coli activation. Our results collectively show that polyphenols derived from CA boost T cell immunity by increasing the number of T cells and its sensitivity towards stimulants and decreasing ROS production by neutrophils that could potentially harm multiple biological systems in aged individuals., (Copyright © 2011 Elsevier Inc. All rights reserved.)

We have previously shown that mesenchymal stem cells (MSC) inhibit tumour cell proliferation, thus promising a novel therapy for treating cancers. In this study, MSC were generated from human bone marrow samples and characterised based on standard immunophenotyping. When MSC were co-cultured with BV173 and Jurkat tumour cells, the proliferation of tumour cells were profoundly inhibited in a dose dependent manner mainly via cell to cell contact interaction. Further cell cycle analysis reveals that MSC arrest tumour cell proliferation in G0/G1 phase of cell cycle thus preventing the entry of tumour cells into S phase of cell cycle.

Background: NMDA receptors expressed by spinal cord neurons in the superficial dorsal horn are involved in the development of chronic pain associated with inflammation and nerve injury. The superficial dorsal horn has a complex and still poorly understood circuitry that is mainly populated by inhibitory and excitatory interneurons. Little is known about how NMDA receptor subunit composition, and therefore pharmacology and voltage dependence, varies with neuronal cell type. NMDA receptors are typically composed of two NR1 subunits and two of four NR2 subunits, NR2A-2D. We took advantage of the differences in Mg2+ sensitivity of the NMDA receptor subtypes together with subtype preferring antagonists to identify the NR2 subunit composition of NMDA receptors expressed on lamina II inhibitory and excitatory interneurons. To distinguish between excitatory and inhibitory interneurons, we used transgenic mice expressing enhanced green fluorescent protein driven by the GAD67 promoter., Results: Analysis of conductance ratio and selective antagonists showed that lamina II GABAergic interneurons express both the NR2A/B containing Mg2+ sensitive receptors and the NR2C/D containing NMDA receptors with less Mg2+ sensitivity. In contrast, excitatory lamina II interneurons express primarily NR2A/B containing receptors. Despite this clear difference in NMDA receptor subunit expression in the two neuronal populations, focally stimulated synaptic input is mediated exclusively by NR2A and 2B containing receptors in both neuronal populations., Conclusions: Stronger expression of NMDA receptors with NR2C/D subunits by inhibitory interneurons compared to excitatory interneurons may provide a mechanism to selectively increase activity of inhibitory neurons during intense excitatory drive that can provide inhibitory feedback.

Bisphosphonates are a common treatment for osteoporosis. Osteonecrosis of the jaw has been associated with the use of bisphosphonates, usually when they have been used parenterally to treat malignancies. Cases associated with oral bisphosphonate as a treatment for osteoporosis are less frequent. We describe two patients exhibiting the clinical manifestations of bisphosphonate-associated osteonecrosis of the jaw. A brief review of the literature on the incidence, possible risk factors, and practice guidelines is also presented.

Dact1 (Dapper/Frodo), an intracellular phosphoprotein that binds Dishevelled, catenins, and other signaling proteins, is expressed in the developing and mature mammalian CNS, but its function there is unknown. Dact1 colocalized with synaptic markers and partitioned to postsynaptic fractions from cultured mouse forebrain neurons. Hippocampal neurons from Dact1 knock-out mice had simpler dendritic arbors and fewer spines than hippocampal neurons from wild-type littermates. This correlated with reductions in excitatory synapses and miniature EPSCs, whereas inhibitory synapses were not affected. Loss of Dact1 resulted in a decrease in activated Rac, and recombinant expression of either Dact1 or constitutively active Rac, but not Rho or Cdc42, rescued dendrite and spine phenotypes in Dact1 mutant neurons. Our findings suggest that, during neuronal differentiation, Dact1 plays a critical role in a molecular pathway promoting Rac activity underlying the elaboration of dendrites and the establishment of spines and excitatory synapses.

NMDA receptors are important elements in pain signaling in the spinal cord dorsal horn. They are heterotetramers typically composed of two NR1 and two of four NR2 subunits: NR2A-2D. Mice lacking specific NR2 subunits show deficits in pain transmission yet subunit location in the spinal cord remains unclear. We have combined electrophysiological and pharmacological approaches to investigate the composition of functional NMDA receptors expressed by lamina I, substance P receptor-expressing (NK1R+) neurons, as well as NK1R- neurons. Under low Mg2+ conditions (100 microM), the conductance of NMDA receptors at -90 mV (g(-90 mV)) with NR2A or NR2B subunits (NR2A/B) is low compared to conductance measured at the membrane potential where the inward current is maximal or maximal inward current (MIC) (ratio of approximately 0.07 calculated from Kuner and Schoepfer, 1996). For NR2C or NR2D subunits (NR2C/D), the ratio is higher (ratio approximately 0.4). NK1R+ and NK1R- neurons express NMDA receptors that give ratios approximately 0.28 and 0.16, respectively, suggesting both types of subunits are present in both populations of neurons, with NK1R+ neurons expressing a higher percentage of NR2C/D type NMDA receptors. This was confirmed using EAB318, an NR2A/B preferring antagonist, and UBP141, a mildly selective NR2C/D antagonist to increase and decrease the g(-90 mV)/g(MIC) ratios in both subpopulations of neurons.

The immune modulatory properties of mesenchymal stem cell (MSC) had brought a new insight in cell-based neotherapy. However, recent works of MSC are focused exclusively on bone marrow-derived MSC. We evaluated the immunogenicity of cord blood-derived MSC (CB-MSC) on T lymphocytes. Human peripheral blood mononuclear cells (PBMC) were prepared by density gradient separation and culture with the presence or absence of CB-MSC. PBMC were collected for activation analysis by flow cytometry at 24-, 48-, and 72- hours. The results showed that, CB-MSC does not stimulate nor inhibit T lymphocyte activation.

Electrolyte disturbances are known to cause acquired Long QT syndrome (LQTS) and Brugada syndrome. While a reduction in INa due to SCN5A mutation is implicated as the underlying mechanism in Brugada syndrome, hyponatremia, which can give rise to a reduced INa, has never been reported in literature as a cause or precipitating factor in this syndrome. We detailed a case in which concomitant-acquired LQTS and Brugada syndrome were associated with severe hypokalemia and hyponatremia following indapamide use for treatment of hypertension and highlighted the potential role of hyponatremia in the pathogenesis of the acquired form of Brugada syndrome.

Mesenchymal stem cells (MSC) are non-haematopoietic stem cells that are capable of differentiating into tissues of mesodermal origin. MSC play an important role in supporting the development of fetal and adult haematopoiesis. More recently, MSC have also been found to exhibit inhibitory effect on T cell responses. However, there is little information on the mechanism of this immunosuppression and our study addresses this issue by targeting T cell functions at various level of immune responses. We have generated MSC from human adult bone marrow (BM) and investigated their immunoregulatory function at different phases of T cell responses. MSC showed the ability to inhibit mitogen (CD3/CD28 microbeads)-activated T cell proliferation in a dose-dependent manner. In order to evaluate the specificity of this immunosuppression, the proliferation of CD4(+) and CD8(+) cells were measured. MSC equally inhibit CD4(+) and CD8(+) subpopulations of T cells in response to PHA stimulation. However, the antiproliferative effect of MSC is not due to the inhibition of T cell activation. The expression of early activation markers of T cells, namely CD25 and CD69 were not significantly altered by MSC at 24, 48 and 72h. Furthermore, the immunosuppressive effect of MSC mainly targets T cell proliferation rather than their effector function since cytotoxicity of T cells is not affected. This work demonstrates that the immunosuppressive effect of MSC is exclusively a consequence of an anti-proliferative activity, which targets T cells of different subpopulations. For this reason, they have the potential to be exploited in the control of unwanted immune responses such as graft versus host disease (GVHD) and autoimmunity.

Blockade of Ca2+-permeable AMPA receptors in the rat spinal cord diminishes the development of hyperalgesia and allodynia associated with peripheral injury. Cobalt uptake studies reveal that Ca2+-permeable AMPA receptors are expressed by some substance P receptor-expressing (NK1R+) neurons in lamina I, as well as other neurons throughout the superficial dorsal horn. Selective elimination of NK1R+ neurons in lamina I and lamina III/IV of the dorsal horn also suppresses development of hyperalgesia and allodynia. These observations raise the possibility that Ca2+-permeable AMPA receptors contribute to excitatory synaptic drive onto the NK1R+ neurons associated with allodynia and hyperalgesia. The first synapse in the pain pathway is the glutamatergic excitatory drive from the primary afferent fibres onto dorsal horn neurons. Therefore, we tested whether Ca2+-permeable AMPA receptors are located on lamina I and lamina III/IV NK1R+ neurons postsynaptic to primary afferent fibres, using inward rectification and polyamine toxins for receptor identification. We examined three different populations of dorsal horn neurons; lamina I NK1R+ neurons, including projection neurons, and non-NK1R+ (NK1R-) neurons including interneurons, and lamina III/IV NK1R+ neurons, believed to contribute to the low-threshold mechanosensory pathway. The majority of synapses in all three groups had rectification indices less than 1.0 and greater than 0.4, indicating that the AMPA receptors at these synapses are a mixture of Ca2+-permeable and -impermeable forms. Lamina III/IV NK1R+ neurons and lamina I NK1R- neurons have a significantly higher proportion of postsynaptic Ca2+-permeable AMPA receptors than lamina I NK1R+ neurons. Thus synaptically positioned Ca2+-permeable AMPA receptors directly contribute to low-threshold sensory afferent drive into the dorsal horn, and can mediate afferent input onto interneurons such as GABAergic neurons. These receptors also contribute to high-threshold primary afferent drive onto NK1R+ neurons in the superficial dorsal horn, but do so less consistently.

The kinetics of activity-dependent, extracellular alkaline transients, and the buffering of extracellular pH (pH(e)), were studied in rat hippocampal slices using a fluorescein-dextran probe. Orthodromic stimuli generated alkaline transients < or = 0.05 pH units that peaked in 273 +/- 26 ms and decayed with a half-time of 508 +/- 43 ms. Inhibition of extracellular carbonic anhydrase (ECA) with benzolamide increased the rate of rise by 25%, doubled peak amplitude, and prolonged the decay three- to fourfold. The slow decay in benzolamide allowed marked temporal summation, resulting in a severalfold increase in amplitude during long stimulus trains. Addition of exogenous carbonic anhydrase reduced the rate of rise, halved the peak amplitude, but had no effect on the normalized decay. A simulation of extracellular buffering kinetics generated recoveries from a base load consistent with the observed decay of the alkaline transient in the presence of benzolamide. Under control conditions, the model approximated the observed decays with an acceleration of the CO2 hydration-dehydration reactions by a factor of 2.5. These data suggest low endogenous ECA activity, insufficient to maintain equilibrium during the alkaline transients. Disequilibrium implies a time-dependent buffering capacity, with a CO2/HCO3- contribution that is small shortly after a base load. It is suggested that within 100 ms, extracellular buffering capacity is about 1% of the value at equilibrium and is provided mainly by phosphate. Accordingly, in the time frame of synaptic transmission, small base loads would generate relatively large changes in interstitial pH.

NMDA receptors have the potential to produce complex activity-dependent regulation of transmitter release when localized presynaptically. In the somatosensory system, NMDA receptors have been immunocytochemically detected on presynaptic terminals of primary afferents, and these have been proposed to drive release of substance P from central terminals of a subset of nociceptors in the spinal cord dorsal horn. Here we report that functional NMDA receptors are indeed present at or near the central terminals of primary afferent fibers. Furthermore, we show that activation of these presynaptic receptors results in an inhibition of glutamate release from the terminals. Some of these NMDA receptors may be expressed in the preterminal axon and regulate the extent to which action potentials invade the extensive central arborizations of primary sensory neurons.

The role of endogenous GABA and ATP in regulating transmitter release from primary afferent terminals in the superficial dorsal horn of the spinal cord is still controversial. ATP is co-released with GABA from some inhibitory dorsal horn neurons raising the possibility that ATP could act in concert with GABA to regulate transmitter release from primary afferent terminals if receptors to both transmitters are expressed there. Using electrophysiology together with immunocytochemistry, we have investigated the expression of ATP-gated P2X and GABAA receptors by identified subpopulations of dorsal root ganglion (DRG) neurons known to project primarily to the superficial dorsal horn. Expression of the heat-sensitive vanilloid receptor 1 (VR1) and sensitivity to capsaicin were used to characterize DRG neurons sensitive to noxious heat. Both P2X and GABAA receptors were expressed on the majority of DRG neurons examined. Recording compound action potentials (CAPs) from dorsal roots in the presence of muscimol, alpha,beta-methylene-ATP (alpha,beta-meATP) or capsaicin resulted in depression of CAP in the slow and medium conducting fibres, indicating cognate receptor expression on the small diameter axons. Dorsal root-evoked dorsal root potentials (DR-DRPs), reflecting depolarization of primary afferent terminals by endogenously released substances, were depressed by the GABAA receptor antagonist SR95531 and alpha,beta-meATP. These results suggest that GABAA and P2X receptors are expressed on DRG cell bodies and slow fibre axons, many of which are heat-nociceptive. These fibres project to the superficial lamina of the dorsal horn where the receptors may function to modulate transmitter release near their central terminals.

This randomised, crossover study compared patient-controlled sedation using boluses of propofol and patient-maintained sedation using a target-controlled infusion of propofol. Twenty-three patients aged 18-35 years having surgical removal of bilateral third molar teeth under local anaesthesia during two separate visits were studied. In the majority of patients, both techniques provided moderate sedation, good operating conditions, stable physiological parameters and a high degree of patient satisfaction. Two patients became over-sedated during patient-controlled sedation. The time taken for titration to adequate sedation was longer with patient-maintained sedation than with patient-controlled sedation [mean (SD) = 8.6 (3.7) min vs. 5.7 (3.1) min, p < 0.005]. The mean overall propofol consumption was similar with both techniques. The majority of patients preferred patient-maintained sedation to patient-controlled sedation, p < 0.05.

No direct evidence has been found for expression of functional AMPA receptors by dorsal root ganglion neurons despite immunocytochemical evidence suggesting they are present. Here we report evidence for expression of functional AMPA receptors by a subpopulation of dorsal root ganglion neurons. The AMPA receptors are most prominently located near central terminals of primary afferent fibers. AMPA and kainate receptors were detected by recording receptor-mediated depolarization of the central terminals under selective pharmacological conditions. We demonstrate that activation of presynaptic AMPA receptors by exogenous agonists causes inhibition of glutamate release from the terminals, possibly via primary afferent depolarization (PAD). These results challenge the traditional view that GABA and GABA(A) receptors exclusively mediate PAD, and indicate that PAD is also mediated by glutamate acting on presynaptically localized AMPA and kainate receptors.