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Sudden unexpected environmental changes capture attention and, when perceived as potentially dangerous, evoke defensive behavioral states. Perturbations of the lateral septum (LS) can produce extreme hyperdefensiveness even to innocuous stimuli, but how this structure influences stimulus-evoked defensive responses and threat perception remains unclear. Here, we show that Crhr2-expressing neurons in mouse LS exhibit phasic activation upon detection of threatening but not rewarding stimuli. Threat-stimulus-driven activity predicts the probability but not vigor or type of defensive behavior evoked. Although necessary for and sufficient to potentiate stimulus-triggered defensive responses, LSCrhr2 neurons do not promote specific behaviors. Rather, their stimulation elicits negative valence and physiological arousal. Moreover, LSCrhr2 activity tracks brain state fluctuations and drives cortical activation and rapid awakening in the absence of threat. Together, our findings suggest that LS directs bottom-up modulation of cortical function to evoke preparatory defensive internal states and selectively enhance responsivity to threat-related stimuli.

The histaminergic neurons of the tuberomammillary nucleus (TMNHDC) of the posterior hypothalamus have long been implicated in promoting arousal. More recently, a role for GABAergic signaling by the TMNHDCneurons in arousal control has been proposed. Here, we investigated the effects of selective chronic disruption of GABA synthesis (via genetic deletion of the GABA synthesis enzyme, glutamic acid decarboxylase 67) or GABAergic transmission (via genetic deletion of the vesicular GABA transporter (VGAT)) in the TMNHDCneurons on sleep–wake in male mice. We also examined the effects of acute chemogenetic activation and optogenetic inhibition of TMNHDCneurons upon arousal in male mice. Unexpectedly, we found that neither disruption of GABA synthesis nor GABAergic transmission altered hourly sleep–wake quantities, perhaps because very few TMNHDCneurons coexpressed VGAT. Acute chemogenetic activation of TMNHDCneurons did not increase arousal levels above baseline but did enhance vigilance when the mice were exposed to a behavioral cage change challenge. Similarly, acute optogenetic inhibition had little effect upon baseline levels of arousal. In conclusion, we could not identify a role for GABA release by TMNHDCneurons in arousal control. Further, if TMNHDCneurons do release GABA, the mechanism by which they do so remains unclear. Our findings support the view that TMNHDCneurons may be important for enhancing arousal under certain conditions, such as exposure to a novel environment, but play only a minor role in behavioral and EEG arousal under baseline conditions.SIGNIFICANCE STATEMENTThe histaminergic neurons of the tuberomammillary nucleus of the hypothalamus (TMNHDC) have long been thought to promote arousal. Additionally, TMNHDCneurons may counter-regulate the wake-promoting effects of histamine through co-release of the inhibitory neurotransmitter, GABA. Here, we show that impairing GABA signaling from TMNHDCneurons does not impact sleep–wake amounts and that few TMNHDCneurons contain the vesicular GABA transporter, which is presumably required to release GABA. We further show that acute activation or inhibition of TMNHDCneurons has limited effects upon baseline arousal levels and that activation enhances vigilance during a behavioral challenge. Counter to general belief, our findings support the view that TMNHDCneurons are neither necessary nor sufficient for the initiation and maintenance of arousal under baseline conditions.

The hypothalamic suprachiasmatic (SCN) clock contains several neurochemically defined cell groups that contribute to the genesis of circadian rhythms. Using cell-specific and genetically targeted approaches we have confirmed an indispensable role for vasoactive intestinal polypeptide-expressing SCN (SCNVIP) neurons, including their molecular clock, in generating the mammalian locomotor activity (LMA) circadian rhythm. Optogenetic-assisted circuit mapping revealed functional, di-synaptic connectivity between SCNVIP neurons and dorsomedial hypothalamic neurons, providing a circuit substrate by which SCNVIP neurons may regulate LMA rhythms. In vivo photometry revealed that while SCNVIP neurons are acutely responsive to light, their activity is otherwise behavioral state invariant. Single-nuclei RNA-sequencing revealed that SCNVIP neurons comprise two transcriptionally distinct subtypes, including putative pacemaker and non-pacemaker populations. Altogether, our work establishes necessity of SCNVIP neurons for the LMA circadian rhythm, elucidates organization of circadian outflow from and modulatory input to SCNVIP cells, and demonstrates a subpopulation-level molecular heterogeneity that suggests distinct functions for specific SCNVIP subtypes., Cell groups in the hypothalamic suprachiasmatic clock contribute to the genesis of circadian rhythms. The authors identified two populations of vasoactive intestinal polypeptide-expressing neurons in the suprachiasmatic nucleus which regulate locomotor circadian rhythm in mice.

During obstructive sleep apnea, elevation of CO2 during apneas contributes to awakening and restoring airway patency. We previously found that glutamatergic neurons in the external lateral parabrachial nucleus (PBel) containing calcitonin gene related peptide (PBelCGRP neurons) are critical for causing arousal during hypercapnia. However, others found that genetic deletion of serotonin (5HT) neurons in the brainstem also prevented arousal from hypercapnia. To examine interactions between the two systems, we showed that dorsal raphe (DR) 5HT neurons selectively targeted the PBel. Either genetically directed deletion or acute optogenetic silencing of DRSert neurons dramatically increased the latency of mice to arouse during hypercapnia, as did silencing DRSert terminals in the PBel. This effect was mediated by 5HT2a receptors which are expressed by PBelCGRP neurons. Our results indicate that the serotonergic input from the DR to the PBel via 5HT2a receptors is critical for modulating the sensitivity of the PBelCGRP neurons that cause arousal to rising levels of blood CO2., Dorsal raphe 5HT(DRSert) neurons regulate arousal from hypercapnia by their projections to the neurons in the external lateral parabrachial nucleus (PBel) that are glutamatergic and also express calcitonin gene related peptide (PBelCGRP). The DRSert input to the PBel modulates the arousal system to rising levels of blood CO2, and may be mediated by 5HT2a receptors on the PBelCGRP neurons.

'Sundowning' in dementia and Alzheimer's disease is characterized by early-evening agitation and aggression. While such periodicity suggests a circadian origin, whether the circadian clock directly regulates aggressive behavior is unknown. We demonstrate that a daily rhythm in aggression propensity in male mice is gated by GABAergic subparaventricular zone (SPZGABA) neurons, the major postsynaptic targets of the central circadian clock, the suprachiasmatic nucleus. Optogenetic mapping revealed that SPZGABA neurons receive input from vasoactive intestinal polypeptide suprachiasmatic nucleus neurons and innervate neurons in the ventrolateral part of the ventromedial hypothalamus (VMH), which is known to regulate aggression. Additionally, VMH-projecting dorsal SPZ neurons are more active during early day than early night, and acute chemogenetic inhibition of SPZGABA transmission phase-dependently increases aggression. Finally, SPZGABA-recipient central VMH neurons directly innervate ventrolateral VMH neurons, and activation of this intra-VMH circuit drove attack behavior. Altogether, we reveal a functional polysynaptic circuit by which the suprachiasmatic nucleus clock regulates aggression.

Basic and clinical observations suggest that the caudal hypothalamus comprises a key node of the ascending arousal system, but the cell types underlying this are not fully understood. Here we report that glutamate-releasing neurons of the supramammillary region (SuMvglut2) produce sustained behavioral and EEG arousal when chemogenetically activated. This effect is nearly abolished following selective genetic disruption of glutamate release from SuMvglut2 neurons. Inhibition of SuMvglut2 neurons decreases and fragments wake, also suppressing theta and gamma frequency EEG activity. SuMvglut2 neurons include a subpopulation containing both glutamate and GABA (SuMvgat/vglut2) and another also expressing nitric oxide synthase (SuMNos1/Vglut2). Activation of SuMvgat/vglut2 neurons produces minimal wake and optogenetic stimulation of SuMvgat/vglut2 terminals elicits monosynaptic release of both glutamate and GABA onto dentate granule cells. Activation of SuMNos1/Vglut2 neurons potently drives wakefulness, whereas inhibition reduces REM sleep theta activity. These results identify SuMvglut2 neurons as a key node of the wake−sleep regulatory system., Supramammillary nucleus (SuM) neurons have been studied in the context of REM sleep but their possible role in mediating wakefulness is not known. Here the authors elucidate the distinct functional contributions of three subpopulations in the SuM on electrographical and behavioral arousal in mice using genetically targeted approaches.

Introduction Optogenetic and chemogenetic studies have shown that activation of basal forebrain (BF) GABAergic neurons rapidly wakes up mice from non-REM (NREM) sleep. These wake-promoting responses have been attributed to BF GABAergic neurons projecting to the cerebral cortex and more specifically to the inhibition of cortical fast-spiking interneurons. Tracing studies have however found that BF GABAergic neurons also densely innervate the lateral hypothalamus (LH) perifornical area, although the role of this pathway in behavioral state control remains mostly unexplored. Methods We conducted in vivo and in vitro optogenetic studies. We selectively expressed channelrhodopsin-2 (ChR2) in BF GABAergic neurons by injecting a cre-dependent viral vector encoding for ChR2 into the BF of VGAT-cre mice. We photostimulated the BF GABAergic input to the LH with optical fibers placed into the LH of EEG instrumented mice. For in vitro recordings we expressed ChR2 in BF GABAergic neurons and we fluorescently labeled orexin or LH GABAergic neurons. We recorded in brain slices from identified orexin neurons or GABA neurons while photostimulating the BF GABAergic input. Results Optogenetic stimulation of the BF GABAergic fibers in the LH produced rapid arousals from NREM sleep. The same stimulation however did not wake up the mice if they were in REM sleep. We conducted additional studies in brain slices to identify the postsynaptic neurons in the LH targeted by the BF GABAergic input. We found that while optogenetic stimulation of the BF GABAergic input did not produce opto-evoked synaptic responses in the orexin neurons, it produced short-latency opto-evoked inhibitory postsynaptic currents (IPSCs) in LH GABAergic neurons. These opto-evoked IPSCs were GABAA receptor-mediated and were maintained in tetrodotoxin (TTX) indicating monosynaptic connectivity. We have previously found that orexin neurons are inhibited by local LH GABAergic neurons. Our hypothesis is that these local GABAergic interneurons are the target of the BF GABAergic arousal input. Conclusion BF GABAergic neurons drive arousal through projections to the LH. We propose that this arousal response is due to the inhibition of local GABAergic interneurons which in turn disinhibit the LH wake-promoting neurons including the orexin neurons. Support (if any) NS091126 and HL149630

A role for the brain’s serotoninergic (5HT) system in the regulation of sleep and wakefulness has been long suggested. Yet, previous studies employing pharmacological, lesion and genetically driven approaches have produced inconsistent findings, leaving 5HT’s role in sleep-wake regulation incompletely understood. Here we sought to define the specific contribution of 5HT neurons within the dorsal raphe nucleus (DRN5HT) to sleep and arousal control. To do this, we employed a chemogenetic strategy to selectively and acutely activate DRN5HT neurons and monitored sleep-wake using electroencephalogram recordings. We additionally assessed indices of anxiety using the open field and elevated plus maze behavioral tests and employed telemetric-based recordings to test effects of acute DRN5HT activation on body temperature and locomotor activity. Our findings indicate that the DRN5HT cell population may not modulate sleep-wake per se, but rather that its activation has apparent anxiolytic properties, suggesting the more nuanced view that DRN5HT neurons are sleep permissive under circumstances that produce anxiety or stress.

Lower urinary tract symptoms (LUTS) are exceptionally common and debilitating, and are likely caused or exacerbated by dysfunction of neural circuits controlling bladder function. An incomplete understanding of neural control of bladder function limits our ability to clinically address LUTS. Barrington’s nucleus (Bar) provides descending control of bladder and sphincter function, and its glutamatergic neurons expressing corticotropin releasing hormone (Bar(Crh/Vglut2)) are implicated in bladder control. However, it remains unclear whether this subset of Bar neurons are necessary for voiding, and the broader circuitry providing input to this control center remains largely unknown. Here we examine the contribution to micturition behavior of Bar(Crh/Vglut2) neurons relative to the overall Bar(Vglut2) population. First, we identify robust, excitatory synaptic input to Bar. Glutamatergic axons from the periaqueductal gray (PAG) and lateral hypothalamic area (LHA) intensely innervate and are functionally connected to Bar, and optogenetic stimulation of these axon terminals reliably provokes voiding. Similarly, optogenetic stimulation of Bar(Vglut2) neurons triggers voiding, whereas stimulating the Bar(Crh/Vglut2) subpopulation causes bladder contraction, typically without voiding. Next, we genetically ablate either Bar(Vglut2) or Bar(Crh/Vglut2) neurons and found that only Bar(Vglut2) ablation replicates the profound urinary retention produced by conventional lesions in this region. Fiber photometry recordings reveal that Bar(Vglut2) neuron activity precedes increased bladder pressure, while activity of Bar(Crh/Vglut2) is phase-delayed. Finally, deleting Crh from Bar neurons has no effect on voiding and related bladder physiology. Our results help identify the circuitry that modulates Bar neuron activity, and identify subtypes that may serve different roles in micturition.

Summary Among the neuronal populations implicated in sleep-wake control, the ventrolateral preoptic (VLPO) nucleus has emerged as a key sleep-promoting center. However, the synaptic drives that regulate the VLPO to control arousal levels in vivo have not to date been identified. Here, we show that sleep-promoting galaninergic neurons within the VLPO nucleus, defined pharmacologically and by single-cell transcript analysis, are postsynaptic targets of lateral hypothalamic GABAergic (LHGABA) neurons and that activation of this pathway in vivo rapidly drives wakefulness. Ca2+ imaging from LHGABA neurons indicate that they are both wake and rapid eye movement (REM)-sleep active. Consistent with the potent arousal-promoting property of the LHGABA → VLPO pathway, presynaptic inputs to LHGABA neurons originate from several canonical stress- and arousal-related network nodes. This work represents the first demonstration that direct synaptic inhibition of the VLPO area can suppress sleep-promoting neurons to rapidly promote arousal.

Optogenetics and chemogenetics are powerful tools, allowing the specific activation or inhibition of targeted neuronal subpopulations. Application of these techniques to sleep and circadian research has resulted in the unveiling of several neuronal populations that are involved in sleep–wake control, and allowed a comprehensive interrogation of the circuitry through which these nodes are coordinated to orchestrate the sleep–wake cycle. In this review, we discuss six recently described sleep–wake and circadian circuits that show promise as therapeutic targets for sleep medicine. The parafacial zone (PZ) and the ventral tegmental area (VTA) are potential druggable targets for the treatment of insomnia. The brainstem circuit underlying rapid eye movement sleep behavior disorder (RBD) offers new possibilities for treating RBD and neurodegenerative synucleinopathies, whereas the parabrachial nucleus, as a nexus linking arousal state control and breathing, is a promising target for developing treatments for sleep apnea. Therapies that act upon the hypothalamic circuitry underlying the circadian regulation of aggression or the photic regulation of arousal and mood pathway carry enormous potential for helping to reduce the socioeconomic burden of neuropsychiatric and neurodegenerative disorders on society. Intriguingly, the development of chemogenetics as a therapeutic strategy is now well underway and such an approach has the capacity to lead to more focused and less invasive therapies for treating sleep–wake disorders and related comorbidities.

The largest synaptic input to the sleep-promoting ventrolateral preoptic area (VLPO) [1] arises from the lateral hypothalamus [2], a brain area associated with arousal [3-5]. However, the neurochemical identity of the majority of these VLPO-projecting neurons within the lateral hypothalamus (LH), as well as their function in the arousal network, remains unknown. Herein we describe a population of VLPO-projecting neurons in the LH that express the vesicular GABA transporter (VGAT; a marker for GABA-releasing neurons). In addition to the VLPO, these neurons also project to several other established sleep and arousal nodes, including the tuberomammillary nucleus, ventral periaqueductal gray, and locus coeruleus. Selective and acute chemogenetic activation of LH VGAT(+) neurons was profoundly wake promoting, whereas acute inhibition increased sleep. Because of its direct and massive inputs to the VLPO, this population may play a particularly important role in sleep-wake switching.

Introduction A role for vasoactive intestinal peptide (VIP) in promoting rapid eye movement (REM) sleep has been suggested, but the anatomical location of the neurons that release VIP to promote REM sleep has not been identified. Here, we investigated the role of VIP-containing cell groups in the ventromedial preoptic area (VMPOVIP) in sleep-wake regulation. The VMPO has also previously been implicated in thermoregulation and the febrile response. Methods We first investigated the native firing activity of VMPOVIP neurons, over repeated sleep-wake cycles, using in vivo fiber photometry in VIP-ires-Cre mice. We next examined the afferent and efferent profile of this cell group using conditional retrograde (pseudotyped modified rabies) and anterograde (adeno-associated viral vector-based) tracers. We finally utilized a chemogenetic strategy to selectively activate VMPOVIP neurons cells while monitoring electroencephalogram/electromyogram activity and core body temperature, in order to determine their role in sleep-wake and thermoregulatory control. Results We found that VMPOVIP cells were predominantly and strikingly REM-active, that they received many synaptic inputs from surrounding hypothalamic regions (including the ventromedial hypothalamus, dorsomedial hypothalamus and the arcuate nucleus), and that they targeted established sleep-wake nodes, such as the ventrolateral preoptic nucleus, tuberomammillary nucleus, lateral hypothalamus and ventrolateral periaqueductal gray area. To our surprise, chemogenetic activation of the VMPOVIP cell population had little effect upon all measures of sleep-wake analysed and no effect upon core body temperature. Conclusion We conclude that VMPOVIP neurons do not promote REM sleep per se. However, their REM-active profile and anatomical connectivity suggest that these neurons may play a functional role in generating certain cardinal features of REM sleep, which is an active focus of on-going research in our laboratory. Support SRSF CDA #016-JP-17 to A.V. and NS073613, NS092652 and NS103161 to P.M.

Patients with Sickle Cell Disease (SCD) frequently present for emergency care with pain or fever. The rate of emergency visits/year is between 2-4 per patient every year with 12% of patients visiting the emergency 4 or more times/year1. National medical organizations in Canada and the United States recommend pain therapy within 30 minutes of arriving to the emergency department2,3. Feedback from patients in Canada reflected a lack of awareness of the medical community regarding the disease and optimal management. As a response Canadian Haemoglobinopathy Association2 (CanHaem), created the "Sickle Cell Disease Emergency Wallet Cards" which were inspired from the successful Hemophilia "Factor First Card4". The goal of the cards was to provide simple care instructions to an emergency responder and facilitate timely care for patients in crisis. These wallet cards have recommendations for treatment of pain and fever within 30 minutes, patient's diagnosis, program contact details, and patient's individual pain plan. The cards have been in circulation for 4 years. The purpose of this study was to determine if the cards are used by parents and patients as intended. Research Questions: 1.Are the CanHaem Cards used by patients and families? 2. Do patients find the card helpful in facilitating their care delivery? Methods: The surveys were administered to patients and/or proxies. Prior to survey distribution three parents/patients have verified the utility of the questions, the content and the readability of the survey. The survey was translated into French/Arabic by two independent translators per language. It was distributed in Alberta and British Columbia, Canada in specialty clinics known to use the cards. The University of Alberta Ethics Board deemed the project a quality improvement initiative and the ARECCI tool: A pRoject Ethics Community Consensus Initiative was completed prior to quality improvement project start. Results: 140/184 participants completed the survey. The response rate: 76%. Demographics: 91% province of Alberta. Proxy: 49%; Patients: 51%. The majority of respondents were female: 54%, median age: 37 years (range 16-84 years). See graphs 1-4 below: 72.3% felt the card was helpful in their care. 78.6% carry the physical card (purse, wallet, and diaper bag), while 10.7% have a picture on their phone, 9.3% don't carry the card, 7.1% state they never received a card. The majority (63.6%) show the card at first contact in emergency, 48.9% felt staff read the card. Total of 68 comments. 67.6% of comments were positive: "Sense of security"; "Get us in to see the doctor faster..." Neutral comments (22%) ranged from requests for lamination to provider response to the card being variable "sometimes it is faster and sometime(s) doesn't really change anything". Finally, 10% were negative reflecting long wait times "Good concept, the idea itself is great. Execution... could be improved greatly", and requests for more information on the card. Conclusion: In Canada, SCD is an uncommon disease and many healthcare providers may not be aware of national and international guidelines regarding acute presentations. To help facilitate knowledge transfer and to aid communication with emergency services, CanHaem created wallet cards as a Canada-wide initiative. This survey demonstrates the patient/parent perspective of the emergency cards. Eighty-nine percent of patients/proxies carried the card (either digitally or physically) and 63% showed the card in the acute care setting. The discrepancy between those who carry the card and those who show it may reflect that numerous respondents stated they had not required emergency care since receiving the card as well some respondents were "carried away by the pain and forget to use the card". Comments revealed a sense of security and patient's appreciation for having the card available to them indicating the value of card to patients. The card demonstrates a simple and low cost intervention to facilitate emergency care for hemoglobinopathy patients. References: 1. Paulukonis ST et al. Emergency department utilization by Californians with sickle cell disease. Ped Blood and Ca 2017. doi: 1002/pbc.26390 2. CanHaem https://www.canhaem.org/healthcare-professionals/ 3. Evidence-Based Management of Sickle Cell Disease: Expert Panel, 2014. 4. Canadian Hemophilia Society. Stop the Bleeding. https://www.hemophilia.ca/files/ER%20CARD%20E_%20Jan%2009.pdf Figure Disclosures Ezzat: Novartis: Honoraria, Speakers Bureau; ApoPharma: Research Funding.

Recent studies have identified an especially important role for basal forebrain GABAergic (BFVGAT) neurons in the regulation of behavioral waking and fast cortical rhythms associated with cognition. However, BFVGATneurons comprise several neurochemically and anatomically distinct subpopulations, including parvalbumin-containing BFVGATneurons and somatostatin-containing BFVGATneurons (BFSOMneurons), and it was recently reported that optogenetic activation of BFSOMneurons increases the probability of a wakefulness to non-rapid-eye movement (NREM) sleep transition when stimulated during the rest period of the animal. This finding was unexpected given that most BFSOMneurons are not NREM sleep active and that central administration of the synthetic somatostatin analog, octreotide, suppresses NREM sleep or increases REM sleep. Here we used a combination of genetically driven chemogenetic and optogenetic activation, chemogenetic inhibition, and ablation approaches to further explore thein vivorole of BFSOMneurons in arousal control. Our findings indicate that acute activation or inhibition of BFSOMneurons is neither wakefulness nor NREM sleep promoting and is without significant effect on the EEG, and that chronic loss of these neurons is without effect on total 24 h sleep amounts, although a small but significant increase in waking was observed in the lesioned mice during the early active period. Ourin vitrocell recordings further reveal electrophysiological heterogeneity in BFSOMneurons, specifically suggesting at least two distinct subpopulations. Together, our data support the more nuanced view that BFSOMneurons are electrically heterogeneous and are not NREM sleep or wake promoting per se, but may exert, in particular during the early active period, a modest inhibitory influence on arousal circuitry.SIGNIFICANCE STATEMENTThe cellular basal forebrain (BF) is a highly complex area of the brain that is implicated in a wide range of higher-level neurobiological processes, including regulating and maintaining normal levels of electrocortical and behavioral arousal. The respectivein vivoroles of BF cell populations and their neurotransmitter systems in the regulation of electrocortical and behavioral arousal remains incompletely understood. Here we seek to define the neurobiological contribution of GABAergic somatostatin-containing BF neurons to arousal control. Understanding the respective contribution of BF cell populations to arousal control may provide critical insight into the pathogenesis of a host of neuropsychiatric and neurodegenerative disorders, including Alzheimer's disease, Parkinson's disease, schizophrenia, and the cognitive impairments of normal aging.

Wakefulness, along with fast cortical rhythms and associated cognition, depend on the basal forebrain (BF). BF cholinergic cell loss in dementia and the sedative effect of anti-cholinergic drugs have long implicated these neurons as important for cognition and wakefulness. The BF also contains intermingled inhibitory GABAergic and excitatory glutamatergic cell groups whose exact neurobiological roles are unclear. Here we show that genetically targeted chemogenetic activation of BF cholinergic or glutamatergic neurons in behaving mice produced significant effects on state consolidation and/or the electroencephalogram but had no effect on total wake. Similar activation of BF GABAergic neurons produced sustained wakefulness and high-frequency cortical rhythms, whereas chemogenetic inhibition increased sleep. Our findings reveal a major contribution of BF GABAergic neurons to wakefulness and the fast cortical rhythms associated with cognition. These findings may be clinically applicable to manipulations aimed at increasing forebrain activation in dementia and the minimally conscious state., The mammalian basal forebrain controls cortical rhythm and wake-sleep. Anaclet et al. use genetically-targeted chemogenetic systems to activate or inhibit cholinergic, glutamatergic or GABAergic neurons in this region, and reveal their contributions to behavioral and electrocortical arousal in behaving mice.

Hypothalamic hypocretin/orexin (Hcrt/Orx) neurons recently emerged as critical regulators of sleep–wake cycles, reward seeking and body energy balance. However, at the level of cellular and network properties, it remains unclear whether Hcrt/Orx neurons are one homogeneous population, or whether there are several distinct types of Hcrt/Orx cells. Here, we collated diverse structural and functional information about individual Hcrt/Orx neurons in mouse brain slices, by combining patch-clamp analysis of spike firing, membrane currents and synaptic inputs with confocal imaging of cell shape and subsequent 3-dimensional Sholl analysis of dendritic architecture. Statistical cluster analysis of intrinsic firing properties revealed that Hcrt/Orx neurons fall into two distinct types. These two cell types also differ in the complexity of their dendritic arbour, the strength of AMPA and GABAA receptor-mediated synaptic drive that they receive, and the density of low-threshold, 4-aminopyridine-sensitive, transient K+ current. Our results provide quantitative evidence that, at the cellular level, the mouse Hcrt/Orx system is composed of two classes of neurons with different firing properties, morphologies and synaptic input organization.

Hypothalamic hypocretin/orexin (hcrt/orx) neurons promote arousal and reward seeking, while reduction in their activity has been linked to narcolepsy, obesity and depression. However, the mechanisms influencing the activity of hcrt/orx networks in situ are not fully understood. Here we show that glycine, a neurotransmitter best known for its actions in the brainstem and spinal cord, elicits dose dependent postsynaptic Cl⁻ currents in hcrt/orx cells in acute mouse brain slices. The effect was blocked by the glycine receptor (GLyR) antagonist strychnine and mimicked by the GlyR agonist alanine. Postsynaptic GlyRs on hcrt/orx cells remained functional during both early postnatal and adult periods, and gramicidin-perforated patch-clamp recordings revealed that they progressively switch from excitatory to inhibitory during the first two postnatal weeks. The pharmacological profile of the glycine response suggested that developed hcrt/orx neurons contain α/β-heteromeric GlyRs that lack α2-subunits, whereas α2-subunits, whereas α2-subunits are present in early postnatal hcrt/orx neurons. All postsynaptic currents (PSCs) in developed hcrt/orx cells were blocked by inhibitors of GABA and glutamate receptors, with no evidence of GlyR-mediated PSCs. However, the frequency but not amplitude of miniature PSCs was reduced by strychnine and increased by glycine in ~50% of hcrt/orx neurons. Together, these results provide the first evidence for functional GlyRs in identified hcrt/orx circuits and suggest that the activity of developed hcrt/orx cells is regulated by two GlyR pools: inhibitory extrasynaptic GlyRs located on all hcrt/orx cells and excitatory GlyRs located on presynaptic terminals contacting some hcrt/orx cells.

The precise neural circuitry that mediates arousal during sleep apnea is not known. We previously found that glutamatergic neurons in the external lateral parabrachial nucleus (PBel) play a critical role in arousal to elevated CO2 or hypoxia. Because many of the PBel neurons that respond to CO2 express calcitonin gene-related peptide (CGRP), we hypothesized that CGRP may provide a molecular identifier of the CO2 arousal circuit. Here, we report that selective chemogenetic and optogenetic activation of PBelCGRP neurons caused wakefulness, whereas optogenetic inhibition of PBelCGRP neurons prevented arousal to CO2, but not to an acoustic tone or shaking. Optogenetic inhibition of PBelCGRP terminals identified a network of forebrain sites under the control of a PBelCGRP switch that is necessary to arouse animals from hypercapnia. Our findings define a novel cellular target for interventions that may prevent sleep fragmentation and the attendant cardiovascular and cognitive consequences seen in obstructive sleep apnea. VIDEO ABSTRACT.

INTRODUCTION: New immigrant families from continental Africa account for an increasing proportion of pediatric patients with Sickle Cell Disease (SCD) in Canada and North America. As families enter the western medical system they face a myriad of tests and medications as well they encounter language barriers, endless forms and large teams. Previous experiences with healthcare also influence families' expectations and adjustment.There is no published data exploring the experiences of these families to help guide practice. Resources such as the Canadian Pediatric Society guide on immigrant health are not specific to SCD. We set out to examine cultural sensitivity methodologically in order to improve delivery of care. Research Questions: What are newcomer families' experiences with SCD in Canada and their home country?What are the prevailing values and beliefs related to SCD that shape the attitude and behaviors of newcomer families?How do newcomer families perceivethe current delivery of medical care (the barriers and the facilitators)? METHODS: Focused ethnography was used to understand the socio-cultural context in which newcomer families from Africa experience their child's SCD; to explore their perspectives, beliefs, how they manage daily life and experience the western medical system. A sample size of12-15 participants was selected to reach saturation.Participants were selected using purposeful and convenience sampling and semi-structured interviews were held with the primary caregiver(s) with use of aninterpreter if needed. Research Ethics Board approved. RESULTS: Saturation was reached at 10 families and 12 were interviewed due to recruiting methods. Demographics:12 caregivers (N=8 females; N=4 males); most were in their forties and from Congo, Nigeria or Liberia. The majority had 3 or more children, were married and employed. The majority did not have extended family within the region. Languages spoken at home were English, French, Yoruba, Swahili orMoorie. They immigrated to Canada between 2002 and 2015 For themes see table 1. CONCLUSIONS: Participants' attitude, perception and knowledge about SCD were profoundly affected by their experiences in their countries of origin. These mostly negative experiences (seeing children suffering without appropriate medical care; observing social stigma, etc.) were deeply embedded and determined their response to SCD in their children. 1. Practice guideline: Allow for sufficient time and provision oftranslation services to explore the families' experience with stigma within country of residence and origin as well as embedded in the healthcare system and the community. Despite the prevalence of SCD in their home countries the diagnosis was a surprise. The path towards acceptance was slow, emotionally convoluted and not linear. Acceptance of the diagnosis is a process and devastating in the context of previous experiences. 2. Practice guideline: Review diagnostic information early and have easily accessible information about SCD available for parents/family network. This information will also need to be reviewed with the child at key developmental time periods. SCD has a dominant impact on life causing renegotiation of all relationships: spousal, family, community, co-workers and school staff. Managing SCD influenced daily routines imposing structure which was disrupted for hospitalizations. Families were reluctant to leave children unattended in the hospital and thus sacrificed personal and employment goals. Social support is limited and families cope alone.Families tend to seek practical support and deny the desire for emotional support. 3. Practice guideline: 3a)Screen for potential isolation and explore whether other caretakers are aware of diagnosis and disease specific care 3b) Given the tendency to deny emotional support needs, lack of nearby extended family and the stigma in the community setting up networks that provide both practical and instrumental support could be meaningful and more likely utilized resources. The life-long complexity of SCD creates anxiety for the child's life expectancy. Families trust in medical expertise, improvements in medical treatments and their faith/religious beliefs are foundations for hope. 4. Practice guideline: HCP working with families should ensure awareness of clinical advances and develop means to easily share knowledge as it will strengthen hope for the future. Table 1 Table 1. Disclosures Bruce: Novartis: Consultancy, Honoraria; Apopharma: Consultancy.

Central orexin/hypocretin neurons promote wakefulness, feeding and reward-seeking, and control blood glucose levels by regulating sympathetic outflow to the periphery. Glucose itself directly suppresses the electrical activity and cytosolic calcium levels of orexin cells. Recent in vitro studies suggested that glucose inhibition of orexin cells may be mechanistically unusual, because it persists under conditions where glucose metabolism is unlikely. To investigate this further, and to clarify whether background metabolic state regulates orexin cell glucosensing, here we analysed glucose responses of orexin cells in mouse brain slices, in the presence and absence of metabolic inhibitors and physiological energy substrates. Consistent with their documented insensitivity to glucokinase inhibitors, the glucose responses of orexin cells persisted in the presence of the mitochondrial poison oligomycin or the glial toxin fluoroacetate. Unexpectedly, in the presence of oligomycin, the magnitude of the glucose response was significantly enhanced. In turn, 2-deoxyglucose, a non-metabolizable glucose analogue, elicited larger responses than glucose. Conversely, intracellular pyruvate dose-dependently suppressed the glucose responses, an effect that was blocked by oligomycin. The glucose responses were also suppressed by intracellular lactate and ATP. Our new data suggest that other energy substrates not only fail to mimic the orexin glucose response, but paradoxically suppress it in a metabolism-dependent manner. We propose that this unexpected intrinsic property of orexin cells allows them to act as 'conditional glucosensors' that preferentially respond to glucose during reduced background energy levels.

Hypothalamic hypocretin/orexin (hcrt/orx) neurons promote arousal and reward seeking, while reduction in their activity has been linked to narcolepsy, obesity and depression. However, the mechanisms influencing the activity of hcrt/orx networks in situ are not fully understood. Here we show that glycine, a neurotransmitter best known for its actions in the brainstem and spinal cord, elicits dose dependent postsynaptic Cl⁻ currents in hcrt/orx cells in acute mouse brain slices. The effect was blocked by the glycine receptor (GLyR) antagonist strychnine and mimicked by the GlyR agonist alanine. Postsynaptic GlyRs on hcrt/orx cells remained functional during both early postnatal and adult periods, and gramicidin-perforated patch-clamp recordings revealed that they progressively switch from excitatory to inhibitory during the first two postnatal weeks. The pharmacological profile of the glycine response suggested that developed hcrt/orx neurons contain α/β-heteromeric GlyRs that lack α2-subunits, whereas α2-subunits, whereas α2-subunits are present in early postnatal hcrt/orx neurons. All postsynaptic currents (PSCs) in developed hcrt/orx cells were blocked by inhibitors of GABA and glutamate receptors, with no evidence of GlyR-mediated PSCs. However, the frequency but not amplitude of miniature PSCs was reduced by strychnine and increased by glycine in ~50% of hcrt/orx neurons. Together, these results provide the first evidence for functional GlyRs in identified hcrt/orx circuits and suggest that the activity of developed hcrt/orx cells is regulated by two GlyR pools: inhibitory extrasynaptic GlyRs located on all hcrt/orx cells and excitatory GlyRs located on presynaptic terminals contacting some hcrt/orx cells.