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1.
Res Sq ; 2024 Jul 12.
Article in English | MEDLINE | ID: mdl-39041039

ABSTRACT

The secretion of cortisol in humans and corticosterone (Cort) in rodents follows a daily rhythm which is important in readying the individual for the daily active cycle and is impaired in chronic depression. This rhythm is orchestrated by the suprachiasmatic nucleus (SCN) which governs the activity of neurons in the paraventricular nucleus of the hypothalamus that produce the corticotropin-releasing hormone (PVHCRH neurons). The dorsomedial nucleus of the hypothalamus (DMH) serves as a crucial intermediary, being innervated by the SCN both directly and via relays in the subparaventricular zone, and projecting axons to the PVH, thereby exerting influence over the cortisol/corticosterone rhythm. However, the role and synaptic mechanisms by which DMH neurons regulate the daily rhythm of Cort secretion has not been explored. We found that either ablating or acutely inhibiting the DMH glutamatergic (DMHVglut2) neurons resulted in a 40-70% reduction in the daily peak of Cort. Deletion of the Vglut2 gene within the DMH produced a similar effect, highlighting the indispensable role of glutamatergic signaling. Chemogenetic stimulation of DMHVglut2 neurons led to an increase of Cort levels, and optogenetic activation of their terminals in the PVH in hypothalamic slices directly activated PVHCRH neurons through glutamate release (the DMHVglut2 → PVHCRH pathway). Similarly, ablating, inhibiting, or disrupting GABA transmission by DMH GABAergic (DMHVgat) neurons diminished the circadian peak of Cort, particularly under constant darkness conditions. Chemogenetic stimulation of DMHVgat neurons increased Cort, although with a lower magnitude compared to DMHVglut2 neuron stimulation, suggesting a role in disinhibiting PVHCRH neurons. Supporting this hypothesis, we found that rostral DMHVgat neurons project directly to GABAergic neurons in the caudal ventral part of the PVH and adjacent peri-PVH area (cvPVH), which directly inhibit PVHCRH neurons, and that activating the DMHVgat terminals in the cvPVH in brain slices reduced GABAergic afferent input onto the PVHCRH neurons. Finally, ablation of cvPVHVgat neurons resulted in increased Cort release at the onset of the active phase, affirming the pivotal role of the DMHVgat → cvPVHVgat → PVHCRH pathway in Cort secretion. In summary, our study delineates two parallel pathways transmitting temporal information to PVHCRH neurons, collectively orchestrating the daily surge in Cort in anticipation of the active phase. These findings are crucial to understand the neural circuits regulating Cort secretion, shedding light on the mechanisms governing this physiological process and the coordinated interplay between SCN, DMH, and PVH.

2.
bioRxiv ; 2024 May 08.
Article in English | MEDLINE | ID: mdl-38766214

ABSTRACT

The parabrachial nucleus (PB), located in the dorsolateral pons, contains primarily glutamatergic neurons which regulate responses to a variety of interoceptive and cutaneous sensory signals. The lateral PB subpopulation expressing the Calca gene which produces the neuropeptide calcitonin gene-related peptide (CGRP) relays signals related to threatening stimuli such as hypercarbia, pain, and nausea, yet the afferents to these neurons are only partially understood. We mapped the afferent projections to the lateral part of the PB in mice using conventional cholera toxin B subunit (CTb) retrograde tracing, and then used conditional rabies virus retrograde tracing to map monosynaptic inputs specifically targeting the PB Calca /CGRP neurons. Using vesicular GABA (vGAT) and glutamate (vGLUT2) transporter reporter mice, we found that lateral PB neurons receive GABAergic afferents from regions such as the lateral part of the central nucleus of the amygdala, lateral dorsal subnucleus of the bed nucleus of the stria terminalis, substantia innominata, and the ventrolateral periaqueductal gray. Additionally, they receive glutamatergic afferents from the infralimbic and insular cortex, paraventricular nucleus, parasubthalamic nucleus, trigeminal complex, medullary reticular nucleus, and nucleus of the solitary tract. Using anterograde tracing and confocal microscopy, we then identified close axonal appositions between these afferents and PB Calca /CGRP neurons. Finally, we used channelrhodopsin-assisted circuit mapping to test whether some of these inputs directly synapse upon the PB Calca /CGRP neurons. These findings provide a comprehensive neuroanatomical framework for understanding the afferent projections regulating the PB Calca /CGRP neurons.

3.
Nat Commun ; 15(1): 1966, 2024 Mar 04.
Article in English | MEDLINE | ID: mdl-38438345

ABSTRACT

The "dorsal pons", or "dorsal pontine tegmentum" (dPnTg), is part of the brainstem. It is a complex, densely packed region whose nuclei are involved in regulating many vital functions. Notable among them are the parabrachial nucleus, the Kölliker Fuse, the Barrington nucleus, the locus coeruleus, and the dorsal, laterodorsal, and ventral tegmental nuclei. In this study, we applied single-nucleus RNA-seq (snRNA-seq) to resolve neuronal subtypes based on their unique transcriptional profiles and then used multiplexed error robust fluorescence in situ hybridization (MERFISH) to map them spatially. We sampled ~1 million cells across the dPnTg and defined the spatial distribution of over 120 neuronal subtypes. Our analysis identified an unpredicted high transcriptional diversity in this region and pinpointed the unique marker genes of many neuronal subtypes. We also demonstrated that many neuronal subtypes are transcriptionally similar between humans and mice, enhancing this study's translational value. Finally, we developed a freely accessible, GPU and CPU-powered dashboard ( http://harvard.heavy.ai:6273/ ) that combines interactive visual analytics and hardware-accelerated SQL into a data science framework to allow the scientific community to query and gain insights into the data.


Subject(s)
Ascomycota , Parabrachial Nucleus , Pontine Tegmentum , Humans , Animals , Mice , In Situ Hybridization, Fluorescence , Brain Stem , Locus Coeruleus
4.
bioRxiv ; 2023 Nov 17.
Article in English | MEDLINE | ID: mdl-38014113

ABSTRACT

The "dorsal pons", or "dorsal pontine tegmentum" (dPnTg), is part of the brainstem. It is a complex, densely packed region whose nuclei are involved in regulating many vital functions. Notable among them are the parabrachial nucleus, the Kölliker Fuse, the Barrington nucleus, the locus coeruleus, and the dorsal, laterodorsal, and ventral tegmental nuclei. In this study, we applied single-nucleus RNA-seq (snRNA-seq) to resolve neuronal subtypes based on their unique transcriptional profiles and then used multiplexed error robust fluorescence in situ hybridization (MERFISH) to map them spatially. We sampled ~1 million cells across the dPnTg and defined the spatial distribution of over 120 neuronal subtypes. Our analysis identified an unpredicted high transcriptional diversity in this region and pinpointed many neuronal subtypes' unique marker genes. We also demonstrated that many neuronal subtypes are transcriptionally similar between humans and mice, enhancing this study's translational value. Finally, we developed a freely accessible, GPU and CPU-powered dashboard (http://harvard.heavy.ai:6273/) that combines interactive visual analytics and hardware-accelerated SQL into a data science framework to allow the scientific community to query and gain insights into the data.

5.
Res Sq ; 2023 May 02.
Article in English | MEDLINE | ID: mdl-37205518

ABSTRACT

Many species use a temporary drop in body temperature and metabolic rate (torpor) as a strategy to survive food scarcity. A similar profound hypothermia is observed with activation of preoptic neurons that express the neuropeptides Pituitary Adenylate-Cyclase-Activating Polypeptide (PACAP)1, Brain Derived Neurotrophic Factor (BDNF)2, or Pyroglutamylated RFamide Peptide (QRFP)3, the vesicular glutamate transporter, Vglut24,5 or the leptin receptor6 (LepR), estrogen 1 receptor (Esr1)7 or prostaglandin E receptor 3 (EP3R) in mice8. However, most of these genetic markers are found on multiple populations of preoptic neurons and only partially overlap with one another. We report here that expression of the EP3R marks a unique population of median preoptic (MnPO) neurons that are required both for lipopolysaccharide (LPS)-induced fever9 and for torpor. These MnPOEP3R neurons produce persistent fever responses when inhibited and prolonged hypothermic responses when activated either chemo- or opto-genetically even for brief periods of time. The mechanism for these prolonged responses appears to involve increases in intracellular calcium in individual EP3R-expressing preoptic neurons that persist for many minutes up to hours beyond the termination of a brief stimulus. These properties endow MnPOEP3R neurons with the ability to act as a two-way master switch for thermoregulation.

6.
Sleep ; 45(12)2022 Dec 12.
Article in English | MEDLINE | ID: mdl-36170177

ABSTRACT

STUDY OBJECTIVES: The pedunculopontine tegmental (PPT) nucleus is implicated in many brain functions, ranging from sleep/wake control and locomotion, to reward mechanisms and learning. The PPT contains cholinergic, GABAergic, and glutamatergic neurons with extensive ascending and descending axonal projections. Glutamatergic PPT (PPTvGlut2) neurons are thought to promote wakefulness, but the mechanisms through which this occurs are unknown. In addition, some researchers propose that PPTvGlut2 neurons promote locomotion, yet even though the PPT is a target for deep brain stimulation in Parkinson's disease, the role of the PPT in locomotion is debated. We hypothesized that PPTvGluT2 neurons drive arousal and specific waking behaviors via certain projections and modulate locomotion via others. METHODS: We mapped the axonal projections of PPTvGlut2 neurons using conditional anterograde tracing and then photostimulated PPTvGlut2 soma or their axon terminal fields across sleep/wake states and analyzed sleep/wake behavior, muscle activity, and locomotion in transgenic mice. RESULTS: We found that stimulation of PPTvGlut2 soma and their axon terminals rapidly triggered arousals from non-rapid eye movement sleep, especially with activation of terminals in the basal forebrain (BF) and lateral hypothalamus (LH). With photoactivation of PPTvGlut2 terminals in the BF and LH, this wakefulness was accompanied by locomotion and other active behaviors, but stimulation of PPTvGlut2 soma and terminals in the substantia nigra triggered only quiet wakefulness without locomotion. CONCLUSIONS: These findings demonstrate the importance of the PPTvGluT2 neurons in driving various aspects of arousal and show that heterogeneous brain nuclei, such as the PPT, can promote a variety of behaviors via distinct axonal projections.


Subject(s)
Basal Forebrain , Wakefulness , Animals , Mice , Wakefulness/physiology , Neurons/physiology , Sleep/physiology , Axons
7.
Nat Commun ; 13(1): 4163, 2022 07 18.
Article in English | MEDLINE | ID: mdl-35851580

ABSTRACT

Humans and animals lacking orexin neurons exhibit daytime sleepiness, sleep attacks, and state instability. While the circuit basis by which orexin neurons contribute to consolidated wakefulness remains unclear, existing models posit that orexin neurons provide their wake-stabilizing influence by exerting excitatory tone on other brain arousal nodes. Here we show using in vivo optogenetics, in vitro optogenetic-based circuit mapping, and single-cell transcriptomics that orexin neurons also contribute to arousal maintenance through indirect inhibition of sleep-promoting neurons of the ventrolateral preoptic nucleus. Activation of this subcortical circuit rapidly drives wakefulness from sleep by differentially modulating the activity of ventrolateral preoptic neurons. We further identify and characterize a feedforward circuit through which orexin (and co-released glutamate) acts to indirectly target and inhibit sleep-promoting ventrolateral preoptic neurons to produce arousal. This revealed circuitry provides an alternate framework for understanding how orexin neurons contribute to the maintenance of consolidated wakefulness and stabilize behavioral state.


Subject(s)
Arousal , Sleep , Animals , Arousal/physiology , Humans , Neurons/physiology , Orexins , Sleep/physiology , Wakefulness/physiology
8.
Int J Mol Sci ; 23(6)2022 Mar 08.
Article in English | MEDLINE | ID: mdl-35328326

ABSTRACT

For over a century, the role of the preoptic hypothalamus and adjacent basal forebrain in sleep-wake regulation has been recognized. However, for years, the identity and location of sleep- and wake-promoting neurons in this region remained largely unresolved. Twenty-five years ago, Saper and colleagues uncovered a small collection of sleep-active neurons in the ventrolateral preoptic nucleus (VLPO) of the preoptic hypothalamus, and since this seminal discovery the VLPO has been intensively investigated by labs around the world, including our own. Herein, we first review the history of the preoptic area, with an emphasis on the VLPO in sleep-wake control. We then attempt to synthesize our current understanding of the circuit, cellular and synaptic bases by which the VLPO both regulates and is itself regulated, in order to exert a powerful control over behavioral state, as well as examining data suggesting an involvement of the VLPO in other physiological processes.


Subject(s)
Preoptic Area , Sleep , Hypothalamus , Learning , Neurons/physiology , Sleep/physiology
9.
Science ; 375(6584): 972-973, 2022 03 04.
Article in English | MEDLINE | ID: mdl-35239395

ABSTRACT

How does dopamine, the brain's pleasure signal, regulate the dream stage of sleep?


Subject(s)
Dreams , Sleep, REM , Dopamine , Dreams/physiology , Sleep , Sleep, REM/physiology
10.
Curr Top Behav Neurosci ; 59: 447-468, 2022.
Article in English | MEDLINE | ID: mdl-34595740

ABSTRACT

Histamine is a small monoamine signaling molecule that plays a role in many peripheral and central physiological processes, including the regulation of wakefulness. The tuberomammillary nucleus is the sole neuronal source of histamine in the brain, and histamine neurons are thought to promote wakefulness and vigilance maintenance - under certain environmental and/or behavioral contexts - through their diffuse innervation of the cortex and other wake-promoting brain circuits. Histamine neurons also contain a number of other putative neurotransmitters, although the functional role of these co-transmitters remains incompletely understood. Within the brain histamine operates through three receptor subtypes that are located on pre- and post-synaptic membranes. Some histamine receptors exhibit constitutive activity, and hence exist in an activated state even in the absence of histamine. Newer medications used to reduce sleepiness in narcolepsy patients in fact enhance histamine signaling by blunting the constitutive activity of these histamine receptors. In this chapter, we provide an overview of the central histamine system with an emphasis on its role in behavioral state regulation and how drugs targeting histamine receptors are used clinically to treat a wide range of sleep-wake disorders.


Subject(s)
Histamine , Sleep , Histamine/physiology , Humans , Hypothalamic Area, Lateral/physiology , Receptors, Histamine , Sleep/physiology , Wakefulness/physiology
11.
Nat Commun ; 11(1): 4410, 2020 09 02.
Article in English | MEDLINE | ID: mdl-32879310

ABSTRACT

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.


Subject(s)
Circadian Rhythm/physiology , Neurons/metabolism , Suprachiasmatic Nucleus , Animals , Brain Mapping , Circadian Clocks/physiology , Locomotion/physiology , Mice , Optogenetics/methods , Suprachiasmatic Nucleus/cytology , Suprachiasmatic Nucleus/metabolism
12.
Nat Commun ; 11(1): 2769, 2020 06 02.
Article in English | MEDLINE | ID: mdl-32488015

ABSTRACT

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.


Subject(s)
Arousal/physiology , Dorsal Raphe Nucleus/metabolism , Hypercapnia/metabolism , Serotonergic Neurons/metabolism , Animals , Brain Stem/metabolism , Calcitonin Gene-Related Peptide/metabolism , Carbon Dioxide , Disease Models, Animal , Male , Mice , Mice, Transgenic , Optogenetics , Parabrachial Nucleus , Serotonin/genetics , Serotonin Plasma Membrane Transport Proteins/genetics
13.
Curr Biol ; 29(24): 4155-4168.e5, 2019 12 16.
Article in English | MEDLINE | ID: mdl-31761703

ABSTRACT

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.


Subject(s)
Preoptic Area/metabolism , Sleep/physiology , Wakefulness/physiology , Animals , Arousal/physiology , Brain/physiology , Electroencephalography/methods , Female , GABAergic Neurons/metabolism , Hypothalamic Area, Lateral/physiology , Hypothalamus/physiology , Male , Mice , Neurons/physiology , Preoptic Area/physiology , Sleep Disorders, Circadian Rhythm/physiopathology
14.
J Neurosci ; 39(45): 8929-8939, 2019 11 06.
Article in English | MEDLINE | ID: mdl-31548232

ABSTRACT

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 TMNHDC neurons 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 TMNHDC neurons on sleep-wake in male mice. We also examined the effects of acute chemogenetic activation and optogenetic inhibition of TMNHDC neurons 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 TMNHDC neurons coexpressed VGAT. Acute chemogenetic activation of TMNHDC neurons 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 TMNHDC neurons in arousal control. Further, if TMNHDC neurons do release GABA, the mechanism by which they do so remains unclear. Our findings support the view that TMNHDC neurons 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 STATEMENT The histaminergic neurons of the tuberomammillary nucleus of the hypothalamus (TMNHDC) have long been thought to promote arousal. Additionally, TMNHDC neurons 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 TMNHDC neurons does not impact sleep-wake amounts and that few TMNHDC neurons contain the vesicular GABA transporter, which is presumably required to release GABA. We further show that acute activation or inhibition of TMNHDC neurons 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 TMNHDC neurons are neither necessary nor sufficient for the initiation and maintenance of arousal under baseline conditions.


Subject(s)
Arousal , Histamine/metabolism , Hypothalamic Area, Lateral/physiology , Neurons/metabolism , gamma-Aminobutyric Acid/metabolism , Action Potentials , Animals , Glutamate Decarboxylase/genetics , Glutamate Decarboxylase/metabolism , Hypothalamic Area, Lateral/cytology , Hypothalamic Area, Lateral/metabolism , Male , Mice , Mice, Inbred C57BL , Neurons/physiology , Sleep , Vesicular Inhibitory Amino Acid Transport Proteins/genetics , Vesicular Inhibitory Amino Acid Transport Proteins/metabolism
15.
Curr Biol ; 29(17): 2775-2789.e7, 2019 09 09.
Article in English | MEDLINE | ID: mdl-31422881

ABSTRACT

Lower urinary tract symptoms (LUTS) are exceptionally common and debilitating, and they 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 (BarCrh/Vglut2) are implicated in bladder control. However, it remains unclear whether this subset of Bar neurons is 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 BarCrh/Vglut2 neurons relative to the overall BarVglut2 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 BarVglut2 neurons triggers voiding, whereas stimulating the BarCrh/Vglut2 subpopulation causes bladder contraction, typically without voiding. Next, we genetically ablate either BarVglut2 or BarCrh/Vglut2 neurons and found that only BarVglut2 ablation replicates the profound urinary retention produced by conventional lesions in this region. Fiber photometry recordings reveal that BarVglut2 neuron activity precedes increased bladder pressure, while activity of BarCrh/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.


Subject(s)
Barrington's Nucleus/physiology , Hypothalamus/metabolism , Mesencephalon/metabolism , Neurons/physiology , Urination/physiology , Animals , Corticotropin-Releasing Hormone/metabolism , Female , Male , Mice , Neurons, Afferent
16.
J Neurosci ; 39(40): 7910-7919, 2019 10 02.
Article in English | MEDLINE | ID: mdl-31420456

ABSTRACT

Proper function of pharyngeal dilator muscles, including the genioglossus muscle of the tongue, is required to maintain upper airway patency. During sleep, the activity of these muscles is suppressed, and as a result individuals with obstructive sleep apnea experience repeated episodes of upper airway closure when they are asleep, in particular during rapid-eye-movement (REM) sleep. Blocking cholinergic transmission in the hypoglossal motor nucleus (MoXII) restores REM sleep genioglossus activity, highlighting the importance of cholinergic transmission in the inhibition of hypoglossal motor neurons (HMNs) during REM sleep. Glutamatergic afferent input from neurons in the parahypoglossal (PH) region to the HMNs is critical for MoXII respiratory motor output. We hypothesized that state-dependent cholinergic regulation may be mediated by this pathway. Here we studied the effects of cholinergic transmission in HMNs in adult male and female mice using patch-clamp recordings in brain slices. Using channelrhodopsin-2-assisted circuit mapping, we first demonstrated that PH glutamatergic neurons directly and robustly activate HMNs (PHGlut → HMNs). We then show that carbachol consistently depresses this input and that this effect is presynaptic. Additionally, carbachol directly affects HMNs by a variable combination of muscarinic-mediated excitatory and inhibitory responses. Altogether, our results suggest that cholinergic signaling impairs upper airway dilator muscle activity by suppressing glutamatergic input from PH premotoneurons to HMNs and by directly inhibiting HMNs. Our findings highlight the complexity of cholinergic control of HMNs at both the presynaptic and postsynaptic levels and provide a possible mechanism for REM sleep suppression of upper airway muscle activity.SIGNIFICANCE STATEMENT Individuals with obstructive sleep apnea can breathe adequately when awake but experience repeated episodes of upper airway closure when asleep, in particular during REM sleep. Similar to skeletal postural muscles, pharyngeal dilator muscles responsible for maintaining an open upper airway become hypotonic during REM sleep. Unlike spinal motoneurons controlling postural muscles that are inhibited by glycinergic transmission during REM sleep, hypoglossal motoneurons that control the upper airway muscles are inhibited in REM sleep by the combination of monoaminergic disfacilitation and cholinergic inhibition. In this study, we demonstrated how cholinergic signaling inhibits hypoglossal motoneurons through presynaptic and postsynaptic muscarinic receptors. Our results provide a potential mechanism for upper airway hypotonia during REM sleep.


Subject(s)
Hypoglossal Nerve/physiopathology , Motor Neurons , Muscle Hypotonia/physiopathology , Parasympathetic Nervous System/physiopathology , Respiratory Muscles/physiopathology , Sleep, REM , Animals , Carbachol/pharmacology , Channelrhodopsins , Female , Glutamates/physiology , Hypoglossal Nerve/drug effects , Male , Mice , Muscarinic Agonists/pharmacology , Neurons, Afferent/drug effects , Neurons, Afferent/physiology , Optogenetics , Parasympathetic Nervous System/drug effects , Patch-Clamp Techniques , Synapses/drug effects
17.
Neuropharmacology ; 154: 34-49, 2019 08.
Article in English | MEDLINE | ID: mdl-30503993

ABSTRACT

The lateral hypothalamus (LH) is a functionally and anatomically complex brain region that is involved in the regulation of many behavioral and physiological processes including feeding, arousal, energy balance, stress, reward and motivated behaviors, pain perception, body temperature regulation, digestive functions and blood pressure. Despite noteworthy experimental efforts over the past decades, the circuit, cellular and synaptic bases by which these different processes are regulated by the LH remains incompletely understood. This knowledge gap links in large part to the high cellular heterogeneity of the LH. Fortunately, the rapid evolution of newer genetic and electrophysiological tools is now permitting the selective manipulation, typically genetically-driven, of discrete LH cell populations. This, in turn, permits not only assignment of function to discrete cell groups, but also reveals that considerable synergistic and antagonistic interactions exist between key LH cell populations that regulate feeding and arousal. For example, we now know that while LH melanin-concentrating hormone (MCH) and orexin/hypocretin neurons both function as sensors of the internal metabolic environment, their roles regulating sleep and arousal are actually opposing. Additional studies have uncovered similarly important roles for subpopulations of LH GABAergic cells in the regulation of both feeding and arousal. Herein we review the role of LH MCH, orexin/hypocretin and GABAergic cell populations in the regulation of energy homeostasis (including feeding) and sleep-wake and discuss how these three cell populations, and their subpopulations, may interact to optimize and coordinate metabolism, sleep and arousal. This article is part of the Special Issue entitled 'Hypothalamic Control of Homeostasis'.


Subject(s)
Eating/physiology , Energy Metabolism/physiology , Hypothalamic Area, Lateral/metabolism , Sleep/physiology , Wakefulness/physiology , Animals , Humans , Neural Pathways/metabolism , Orexins/metabolism
18.
Nat Commun ; 9(1): 4129, 2018 10 08.
Article in English | MEDLINE | ID: mdl-30297727

ABSTRACT

The preoptic area (POA) is necessary for sleep, but the fundamental POA circuits have remained elusive. Previous studies showed that galanin (GAL)- and GABA-producing neurons in the ventrolateral preoptic nucleus (VLPO) express cFos after periods of increased sleep and innervate key wake-promoting regions. Although lesions in this region can produce insomnia, high frequency photostimulation of the POAGAL neurons was shown to paradoxically cause waking, not sleep. Here we report that photostimulation of VLPOGAL neurons in mice promotes sleep with low frequency stimulation (1-4 Hz), but causes conduction block and waking at frequencies above 8 Hz. Further, optogenetic inhibition reduces sleep. Chemogenetic activation of VLPOGAL neurons confirms the increase in sleep, and also reduces body temperature. In addition, chemogenetic activation of VLPOGAL neurons induces short-latency sleep in an animal model of insomnia. Collectively, these findings establish a causal role of VLPOGAL neurons in both sleep induction and heat loss.


Subject(s)
Body Temperature Regulation/physiology , Galanin/metabolism , Neurons/metabolism , Preoptic Area/metabolism , Sleep/physiology , Animals , Body Temperature Regulation/genetics , Electroencephalography , Electromyography , Galanin/genetics , Gene Expression Profiling , Male , Mice, Transgenic , Preoptic Area/cytology , Sleep/genetics , Sleep Initiation and Maintenance Disorders/genetics , Sleep Initiation and Maintenance Disorders/metabolism , Sleep Initiation and Maintenance Disorders/physiopathology
19.
Curr Biol ; 28(14): 2291-2301.e5, 2018 07 23.
Article in English | MEDLINE | ID: mdl-30017482

ABSTRACT

Stress elicits a variety of autonomic responses, including hyperthermia (stress fever) in humans and animals. In this present study, we investigated the circuit basis for thermogenesis and heat conservation during this response. We first demonstrated the glutamatergic identity of the dorsal hypothalamic area (DHAVglut2) neurons that innervate the raphe pallidus nucleus (RPa) to regulate core temperature (Tc) and mediate stress-induced hyperthermia. Then, using chemogenetic and optogenetic methods to manipulate this hypothalamomedullary circuit, we found that activation of DHAVglut2 neurons potently drove an increase in Tc, but surprisingly, stress-induced hyperthermia was only reduced by about one-third when they were inhibited. Further investigation showed that DHAVglut2 neurons activate brown adipose tissue (BAT) but do not cause vasoconstriction, instead allowing reflex tail artery vasodilation as a response to BAT-induced hyperthermia. Retrograde rabies virus tracing revealed projections from DHAVglut2 neurons to RPaVglut3, but not to RPaGABA neurons, and identified a set of inputs to DHAVglut2 → RPa neurons that are likely to mediate BAT activation. The dissociation of the DHAVglut2 thermogenic pathway from the thermoregulatory vasoconstriction (heat-conserving) pathway may explain stress flushing (skin vasodilation but a feeling of being too hot) during stressful times.


Subject(s)
Body Temperature Regulation/physiology , Fever/physiopathology , Hypothalamus/metabolism , Neurons/physiology , Thermogenesis , Animals , Female , Male , Mice , Nucleus Raphe Pallidus/physiology , Optogenetics , Stress, Physiological
20.
J Neurosci ; 38(22): 5168-5181, 2018 05 30.
Article in English | MEDLINE | ID: mdl-29735555

ABSTRACT

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, BFVGAT neurons comprise several neurochemically and anatomically distinct subpopulations, including parvalbumin-containing BFVGAT neurons and somatostatin-containing BFVGAT neurons (BFSOM neurons), and it was recently reported that optogenetic activation of BFSOM neurons 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 BFSOM neurons 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 the in vivo role of BFSOM neurons in arousal control. Our findings indicate that acute activation or inhibition of BFSOM neurons 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. Our in vitro cell recordings further reveal electrophysiological heterogeneity in BFSOM neurons, specifically suggesting at least two distinct subpopulations. Together, our data support the more nuanced view that BFSOM neurons 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 STATEMENT The 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 respective in vivo roles 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.


Subject(s)
Basal Forebrain/physiology , Behavior, Animal/physiology , Neurons/physiology , Somatostatin/physiology , Animals , Basal Forebrain/cytology , Electroencephalography , Electrophysiological Phenomena/physiology , Female , Gene Deletion , Genotype , Male , Mice , Optogenetics , Sleep, Slow-Wave/physiology , Somatostatin/metabolism , Transcriptional Activation , Vesicular Inhibitory Amino Acid Transport Proteins/genetics , Vesicular Inhibitory Amino Acid Transport Proteins/physiology , Wakefulness/physiology
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