Lateral hypothalamic neurotensin neurons promote arousal and hyperthermia

Serum levels of neurotensin, pannexin-1, and sestrin-2 and the correlations with sleep quality or/and cognitive function in the patients with chronic insomnia disorder

Objectives

To examine serum concentrations of neurotensin, pannexin-1 and sestrin-2, and their correlations with subjective and objective sleep quality and cognitive function in the patients with chronic insomnia disorder (CID).

Methods

Sixty-five CID patients were enrolled continuously and fifty-six good sleepers in the same period were served as healthy controls (HCs). Serum levels of neurotensin, pannexin-1 and sestrin-2 were measured by enzyme-linked immunosorbent assays. Sleep quality was assessed with the Pittsburgh Sleep Quality Index (PSQI) and polysomnography, and mood was evaluated by 17-item Hamilton Depression Rating Scale. General cognitive function was assessed with the Chinese-Beijing Version of Montreal Cognitive Assessment and spatial memory was evaluated by Blue Velvet Arena Test (BVAT).

Results

Relative to the HCs, the CID sufferers had higher levels of neurotensin (t=5.210, p<0.001) and pannexin-1 (Z=-4.169, p<0.001), and lower level of sestrin-2 (Z=-2.438, p=0.015). In terms of objective sleep measures, pannexin-1 was positively associated with total sleep time (r=0.562, p=0.002) and sleep efficiency (r=0.588, p=0.001), and negatively with wake time after sleep onset (r=-0.590, p=0.001) and wake time (r=-0.590, p=0.001); sestrin-2 was positively associated with percentage of rapid eye movement sleep (r=0.442, p=0.016) and negatively with non-rapid eye movement sleep stage 2 in the percentage (r=-0.394, p=0.034). Adjusted for sex, age and HAMD, pannexin-1 was still associated with the above objective sleep measures, but sestrin-2 was only negatively with wake time (r=-0.446, p=0.022). However, these biomarkers showed no significant correlations with subjective sleep quality (PSQI score). Serum concentrations of neurotensin and pannexin-1 were positively associated with the mean erroneous distance in the BVAT. Adjusted for sex, age and depression, neurotensin was negatively associated with MoCA score (r=-0.257, p=0.044), pannexin-1 was positively associated with the mean erroneous distance in the BVAT (r=0.270, p=0.033).

Conclusions

The CID patients had increased neurotensin and pannexin-1 and decreased sestrin-2 in the serum levels, indicating neuron dysfunction, which could be related to poor sleep quality and cognitive dysfunction measured objectively.

Distinct lateral hypothalamic CaMKIIα neuronal populations regulate wakefulness and locomotor activity

For nearly a century, evidence has accumulated indicating that the lateral hypothalamus (LH) contains neurons essential to sustain wakefulness. While lesion or inactivation of LH neurons produces a profound increase in sleep, stimulation of inhibitory LH neurons promotes wakefulness. To date, the primary wake-promoting cells that have been identified in the LH are the hypocretin/orexin (Hcrt) neurons, yet these neurons have little impact on total sleep or wake duration across the 24-h period. Recently, we and others have identified other LH populations that increase wakefulness. In the present study, we conducted microendoscopic calcium imaging in the LH concomitant with EEG and locomotor activity (LMA) recordings and found that a subset of LH neurons that express Ca2+/calmodulin-dependent protein kinase IIα (CaMKIIα) are preferentially active during wakefulness. Chemogenetic activation of these neurons induced sustained wakefulness and greatly increased LMA even in the absence of Hcrt signaling. Few LH CaMKIIα-expressing neurons are hypocretinergic or histaminergic while a small but significant proportion are GABAergic. Ablation of LH inhibitory neurons followed by activation of the remaining LH CaMKIIα neurons induced similar levels of wakefulness but blunted the LMA increase. Ablated animals showed no significant changes in sleep architecture but both spontaneous LMA and high theta (8 to 10 Hz) power during wakefulness were reduced. Together, these findings indicate the existence of two subpopulations of LH CaMKIIα neurons: an inhibitory population that promotes locomotion without affecting sleep architecture and an excitatory population that promotes prolonged wakefulness even in the absence of Hcrt signaling.

β-arrestin-biased Allosteric Modulator of Neurotensin Receptor 1 Reduces Ethanol Drinking and Responses to Ethanol Administration in Rodents

Alcohol use disorders (AUDs) impose an enormous societal and financial burden, and world-wide, alcohol misuse is the 7th leading cause of premature death1. Despite this, there are currently only 3 FDA approved pharmacological treatments for the treatment of AUDs in the United States. The neurotensin (Nts) system has long been implicated in modulating behaviors associated with alcohol misuse. Recently, a novel compound, SBI-553, that biases the action of Nts receptor 1 (NTSR1) activation, has shown promise in preclinical models of psychostimulant misuse. Here we investigate the efficacy of this compound to alter ethanol-mediated behaviors in a comprehensive battery of experiments assessing ethanol consumption, behavioral responses to ethanol, sensitivity to ethanol, and ethanol metabolism. Additionally, we investigated behavior in avoidance and cognitive assays to monitor potential side effects of SBI-553. We find that SBI-553 reduces binge-like ethanol consumption in mice without altering avoidance behavior or novel object recognition. We also observe sex-dependent differences in physiological responses to sequential ethanol injections in mice. In rats, we show that SBI-553 attenuates sensitivity to the interoceptive effects of ethanol (using a Pavlovian drug discrimination task). Our data suggest that targeting NTSR1 signaling may be promising to attenuate alcohol misuse, and adds to a body of literature that suggests NTSR1 may be a common downstream target involved in the psychoactive effects of multiple reinforcing substances.

Neurotensin and Neurotensin Receptors in Stress-related Disorders: Pathophysiology & Novel Drug Targets

Neurotensin (NT) is a 13-amino acid neuropeptide widely distributed in the CNS that has been involved in the pathophysiology of many neural and psychiatric disorders. There are three known neurotensin receptors (NTSRs), which mediate multiple actions, and form the neurotensinergic system in conjunction with NT. NTSR1 is the main mediator of NT, displaying effects in both the CNS and the periphery, while NTSR2 is mainly expressed in the brain and NTSR3 has a broader expression pattern. In this review, we bring together up-to-date studies showing an involvement of the neurotensinergic system in different aspects of the stress response and the main stress-related disorders, such as depression and anxiety, post-traumatic stress disorder (PTSD) and its associated symptoms, such as fear memory and maternal separation, ethanol addiction, and substance abuse. Emphasis is put on gene, mRNA, and protein alterations of NT and NTSRs, as well as behavioral and pharmacological studies, leading to evidence-based suggestions on the implicated regulating mechanisms as well as their therapeutic exploitation. Stress responses and anxiety involve mainly NTSR1, but also NTSR2 and NTSR3. NTSR1 and NTSR3 are primarily implicated in depression, while NTSR2 and secondarily NTSR1 in PTSD. NTSR1 is interrelated with substance and drug abuse and NTSR2 with fear memory, while all NTSRs seem to be implicated in ethanol consumption. Some of the actions of NT and NTSRs in these pathological settings may be driven through interactions between NT and corticotrophin releasing factor (CRF) in their regulatory contribution, as well as by NT's pro-inflammatory mediating actions.

Neural Control of REM Sleep and Motor Atonia: Current Perspectives

PURPOSE OF REVIEW

Since the formal discovery of rapid eye movement (REM) sleep in 1953, we have gained a vast amount of knowledge regarding the specific populations of neurons, their connections, and synaptic mechanisms regulating this stage of sleep and its accompanying features. This article discusses REM sleep circuits and their dysfunction, specifically emphasizing recent studies using conditional genetic tools.

RECENT FINDINGS

Sublaterodorsal nucleus (SLD) in the dorsolateral pons, especially the glutamatergic subpopulation in this region (SLDGlut), are shown to be indispensable for REM sleep. These neurons appear to be single REM generators in the rodent brain and may initiate and orchestrate all REM sleep events, including cortical and hippocampal activation and muscle atonia through distinct pathways. However, several cell groups in the brainstem and hypothalamus may influence SLDGlut neuron activity, thereby modulating REM sleep timing, amounts, and architecture. Damage to SLDGlut neurons or their projections involved in muscle atonia leads to REM behavior disorder, whereas the abnormal activation of this pathway during wakefulness may underlie cataplexy in narcolepsy. Despite some opposing views, it has become evident that SLDGlut neurons are the sole generators of REM sleep and its associated characteristics. Further research should prioritize a deeper understanding of their cellular, synaptic, and molecular properties, as well as the mechanisms that trigger their activation during cataplexy and make them susceptible in RBD.

Characterization of TRPM8-expressing neurons in the adult mouse hypothalamus

Transient receptor potential melastatin 8 (TRPM8) is a menthol receptor that detects cold temperatures and influences behaviors and autonomic functions under cold stimuli. Despite the well-documented peripheral roles of TRPM8, the evaluation of its central functions is still of great interest. The present study clarifies the nature of a subpopulation of TRPM8-expressing neurons in the adult mice. Combined in situ hybridization and immunohistochemistry revealed that TRPM8-expressing neurons are exclusively positive for glutamate decarboxylase 67 mRNA signals in the lateral septal nucleus (LS) and preoptic area (POA) but produced no positive signal for vesicular glutamate transporter 2. Double labeling immunohistochemistry showed the colocalization of TRPM8 with vesicular GABA transporter at axonal terminals. Immunohistochemistry further revealed that TRPM8-expressing neurons frequently expressed calbindin and calretinin in the LS, but not in the POA. TRPM8-expressing neurons in the POA expressed a prostaglandin E2 receptor, EP3, and neurotensin, whereas expression in the LS was minimal. These results indicate that hypothalamic TRPM8-expressing neurons are inhibitory GABAergic, while the expression profile of calcium-binding proteins, neurotensin, and EP3 differs between the POA and LS.

Control of energy homeostasis by the lateral hypothalamic area

The lateral hypothalamic area (LHA) is a subcortical brain region that exerts control over motivated behavior, feeding, and energy balance across species. Recent single-cell sequencing studies have defined at least 30 distinct LHA neuron types. Some of these influence specific aspects of energy homeostasis; however, the functions of many LHA cell types remain unclear. This review addresses the rapidly emerging evidence from cell-type-specific investigations that the LHA leverages distinct neuron populations to regulate energy balance through complex connections with other brain regions. It will highlight recent findings demonstrating that LHA control of energy balance extends beyond mere food intake and propose outstanding questions to be addressed by future research.

A common neuronal ensemble in nucleus accumbens regulates pain-like behaviour and sleep

A comorbidity of chronic pain is sleep disturbance. Here, we identify a dual-functional ensemble that regulates both pain-like behaviour induced by chronic constrictive injury or complete Freund's adjuvant, and sleep wakefulness, in the nucleus accumbens (NAc) in mice. Specifically, a select population of NAc neurons exhibits increased activity either upon nociceptive stimulation or during wakefulness. Experimental activation of the ensemble neurons exacerbates pain-like (nociceptive) responses and reduces NREM sleep, while inactivation of these neurons produces the opposite effects. Furthermore, NAc ensemble primarily consists of D1 neurons and projects divergently to the ventral tegmental area (VTA) and preoptic area (POA). Silencing an ensemble innervating VTA neurons selectively increases nociceptive responses without affecting sleep, whereas inhibiting ensemble-innervating POA neurons decreases NREM sleep without affecting nociception. These results suggest a common NAc ensemble that encodes chronic pain and controls sleep, and achieves the modality specificity through its divergent downstream circuit targets.

Structure and Function of Neuronal Circuits Linking Ventrolateral Preoptic Nucleus and Lateral Hypothalamic Area

To understand how sleep-wakefulness cycles are regulated, it is essential to disentangle structural and functional relationships between the preoptic area (POA) and lateral hypothalamic area (LHA), since these regions play important yet opposing roles in the sleep-wakefulness regulation. GABA- and galanin (GAL)-producing neurons in the ventrolateral preoptic nucleus (VLPO) of the POA (VLPOGABA and VLPOGAL neurons) are responsible for the maintenance of sleep, while the LHA contains orexin-producing neurons (orexin neurons) that are crucial for maintenance of wakefulness. Through the use of rabies virus-mediated neural tracing combined with in situ hybridization (ISH) in male and female orexin-iCre mice, we revealed that the vesicular GABA transporter (Vgat, Slc32a1)- and galanin (Gal)-expressing neurons in the VLPO directly synapse with orexin neurons in the LHA. A majority (56.3 ± 8.1%) of all VLPO input neurons connecting to orexin neurons were double-positive for Vgat and Gal Using projection-specific rabies virus-mediated tracing in male and female Vgat-ires-Cre and Gal-Cre mice, we discovered that VLPOGABA and VLPOGAL neurons that send projections to the LHA received innervations from similarly distributed input neurons in many brain regions, with the POA and LHA being among the main upstream areas. Additionally, we found that acute optogenetic excitation of axons of VLPOGABA neurons, but not VLPOGAL neurons, in the LHA of male Vgat-ires-Cre mice induced wakefulness. This study deciphers the connectivity between the VLPO and LHA, provides a large-scale map of upstream neuronal populations of VLPO→LHA neurons, and reveals a previously uncovered function of the VLPOGABA→LHA pathway in the regulation of sleep and wakefulness.SIGNIFICANCE STATEMENT We identified neurons in the ventrolateral preoptic nucleus (VLPO) that are positive for vesicular GABA transporter (Vgat) and/or galanin (Gal) and serve as presynaptic partners of orexin-producing neurons in the lateral hypothalamic area (LHA). We depicted monosynaptic input neurons of GABA- and galanin-producing neurons in the VLPO that send projections to the LHA throughout the entire brain. Their input neurons largely overlap, suggesting that they comprise a common neuronal population. However, acute excitatory optogenetic manipulation of the VLPOGABA→LHA pathway, but not the VLPOGAL→LHA pathway, evoked wakefulness. This study shows the connectivity of major components of the sleep/wake circuitry in the hypothalamus and unveils a previously unrecognized function of the VLPOGABA→LHA pathway in sleep-wakefulness regulation. Furthermore, we suggest the existence of subpopulations of VLPOGABA neurons that innervate LHA.

Control of Emotion and Wakefulness by Neurotensinergic Neurons in the Parabrachial Nucleus

The parabrachial nucleus (PBN) integrates interoceptive and exteroceptive information to control various behavioral and physiological processes including breathing, emotion, and sleep/wake regulation through the neural circuits that connect to the forebrain and the brainstem. However, the precise identity and function of distinct PBN subpopulations are still largely unknown. Here, we leveraged molecular characterization, retrograde tracing, optogenetics, chemogenetics, and electrocortical recording approaches to identify a small subpopulation of neurotensin-expressing neurons in the PBN that largely project to the emotional control regions in the forebrain, rather than the medulla. Their activation induces freezing and anxiety-like behaviors, which in turn result in tachypnea. In addition, optogenetic and chemogenetic manipulations of these neurons revealed their function in promoting wakefulness and maintaining sleep architecture. We propose that these neurons comprise a PBN subpopulation with specific gene expression, connectivity, and function, which play essential roles in behavioral and physiological regulation.

To sleep or not to sleep - Effects on memory in normal aging and disease

Sleep behavior undergoes significant changes across the lifespan, and aging is associated with marked alterations in sleep amounts and quality. The primary sleep changes in healthy older adults include a shift in sleep timing, reduced slow-wave sleep, and impaired sleep maintenance. However, neurodegenerative and psychiatric disorders are more common among the elderly, which further worsen their sleep health. Irrespective of the cause, insufficient sleep adversely affects various bodily functions including energy metabolism, mood, and cognition. In this review, we will focus on the cognitive changes associated with inadequate sleep during normal aging and the underlying neural mechanisms.

Dorsoventral Arrangement of Lateral Hypothalamus Populations in the Mouse Hypothalamus: a Prosomeric Genoarchitectonic Analysis

The lateral hypothalamus (LH) has a heterogeneous cytoarchitectonic organization that has not been elucidated in detail. In this work, we analyzed within the framework of the prosomeric model the differential expression pattern of 59 molecular markers along the ventrodorsal dimension of the medial forebrain bundle in the mouse, considering basal and alar plate subregions of the LH. We found five basal (LH1-LH5) and four alar (LH6-LH9) molecularly distinct sectors of the LH with neuronal cell groups that correlate in topography with previously postulated alar and basal hypothalamic progenitor domains. Most peptidergic populations were restricted to one of these LH sectors though some may have dispersed into a neighboring sector. For instance, histaminergic Hdc-positive neurons were mostly contained within the basal LH3, Nts (neurotensin)- and Tac2 (tachykinin 2)-expressing cells lie strictly within LH4, Hcrt (hypocretin/orexin)-positive and Pmch (pro-melanin-concentrating hormone)-positive neurons appeared within separate LH5 subdivisions, Pnoc (prepronociceptin)-expressing cells were mainly restricted to LH6, and Sst (somatostatin)-positive cells were identified within the LH7 sector. The alar LH9 sector, a component of the Foxg1-positive telencephalo-opto-hypothalamic border region, selectively contained Satb2-expressing cells. Published studies of rodent LH subdivisions have not described the observed pattern. Our genoarchitectonic map should aid in systematic approaches to elucidate LH connectivity and function.

Glutamatergic pedunculopontine tegmental neurons control wakefulness and locomotion via distinct axonal projections

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.

Reactogenic sleepiness after COVID-19 vaccination. A hypothesis involving orexinergic system linked to inflammatory signals

Coronavirus disease 2019 (COVID-19) represents a global healthcare crisis that has led to morbidity and mortality on an unprecedented scale. While studies on COVID-19 vaccines are ongoing, the knowledge about the reactogenic symptoms that can occur after vaccination and its generator mechanisms can be critical for healthcare professionals to improve compliance with the future vaccination campaign. Because sleep and immunity are bidirectionally linked, sleepiness or sleep disturbance side effects reported after some of the COVID-19 vaccines advise an academic research line in the context of physiological or pathological neuroimmune interactions. On the recognized basis of inflammatory regulation of hypothalamic neurons in sickness behavior, we hypothesized that IL-1β, INF-γ and TNF-α pro-inflammatory cytokines inhibit orexinergic neurons promoting sleepiness after peripheral activation of the innate immune system induced by the novel COVID-19 vaccines. In addition, based on knowledge of previous vaccines and disease manifestations of SARS-CoV-2 infection, it also suggests that narcolepsy must be included as potential adverse events of particular interest to consider in pharmacovigilance studies.

Vasopressin neurons in the paraventricular hypothalamus promote wakefulness via lateral hypothalamic orexin neurons

The sleep-wakefulness cycle is regulated by complicated neural networks that include many different populations of neurons throughout the brain. Arginine vasopressin neurons in the paraventricular nucleus of the hypothalamus (PVH^AVP) regulate various physiological events and behaviors, such as body-fluid homeostasis, blood pressure, stress response, social interaction, and feeding. Changes in arousal level often accompany these PVH^AVP-mediated adaptive responses. However, the contribution of PVH^AVP neurons to sleep-wakefulness regulation has remained unknown. Here, we report the involvement of PVH^AVP neurons in arousal promotion. Optogenetic stimulation of PVH^AVP neurons rapidly induced transitions to wakefulness from both NREM and REM sleep. This arousal effect was dependent on AVP expression in these neurons. Similarly, chemogenetic activation of PVH^AVP neurons increased wakefulness and reduced NREM and REM sleep, whereas chemogenetic inhibition of these neurons significantly reduced wakefulness and increased NREM sleep. We observed dense projections of PVH^AVP neurons in the lateral hypothalamus with potential connections to orexin/hypocretin (LH^Orx) neurons. Optogenetic stimulation of PVH^AVP neuronal fibers in the LH immediately induced wakefulness, whereas blocking orexin receptors attenuated the arousal effect of PVH^AVP neuronal activation drastically. Monosynaptic rabies-virus tracing revealed that PVH^AVP neurons receive inputs from multiple brain regions involved in sleep-wakefulness regulation, as well as those involved in stress response and energy metabolism. Moreover, PVH^AVP neurons mediated the arousal induced by novelty stress and a melanocortin receptor agonist melanotan-II. Thus, our data suggested that PVH^AVP neurons promote wakefulness via LH^Orx neurons in the basal sleep-wakefulness and some stressful conditions.

Time to drink: Activating lateral hypothalamic area neurotensin neurons promotes intake of fluid over food in a time-dependent manner

The lateral hypothalamic area (LHA) is essential for ingestive behavior but has primarily been studied in modulating feeding, with comparatively scant attention on drinking. This is partly because most LHA neurons simultaneously promote feeding and drinking, suggesting that ingestive behaviors track together. A notable exception are LHA neurons expressing neurotensin (LHANts neurons): activating these neurons promotes water intake but modestly restrains feeding. Here we investigated the connectivity of LHANts neurons, their necessity and sufficiency for drinking and feeding, and how timing and resource availability influence their modulation of these behaviors. LHANts neurons project broadly throughout the brain, including to the lateral preoptic area (LPO), a brain region implicated in modulating drinking behavior. LHANts neurons also receive inputs from brain regions implicated in sensing hydration and energy status. While activation of LHANts neurons is not required to maintain homeostatic water or food intake, it selectively promotes drinking during the light cycle, when ingestive drive is low. Activating LHANts neurons during this period also increases willingness to work for water or palatable fluids, regardless of their caloric content. By contrast, LHANts neuronal activation during the dark cycle does not promote drinking, but suppresses feeding during this time. Finally, we demonstrate that the activation of the LHANts → LPO projection is sufficient to mediate drinking behavior, but does not suppress feeding as observed after generally activating all LHANts neurons. Overall, our work suggests how and when LHANts neurons oppositely modulate ingestive behaviors.

Hyperexcitable arousal circuits drive sleep instability during aging

Sleep quality declines with age; however, the underlying mechanisms remain elusive. We found that hyperexcitable hypocretin/orexin (Hcrt/OX) neurons drive sleep fragmentation during aging. In aged mice, Hcrt neurons exhibited more frequent neuronal activity epochs driving wake bouts, and optogenetic activation of Hcrt neurons elicited more prolonged wakefulness. Aged Hcrt neurons showed hyperexcitability with lower KCNQ2 expression and impaired M-current, mediated by KCNQ2/3 channels. Single-nucleus RNA-sequencing revealed adaptive changes to Hcrt neuron loss in the aging brain. Disruption of Kcnq2/3 genes in Hcrt neurons of young mice destabilized sleep, mimicking aging-associated sleep fragmentation, whereas the KCNQ-selective activator flupirtine hyperpolarized Hcrt neurons and rejuvenated sleep architecture in aged mice. Our findings demonstrate a mechanism underlying sleep instability during aging and a strategy to improve sleep continuity.

How REM sleep shapes hypothalamic computations for feeding behavior

The electrical activity of diverse brain cells is modulated across states of vigilance, namely wakefulness, non-rapid eye movement (NREM) sleep, and rapid eye movement (REM) sleep. Enhanced activity of neuronal circuits during NREM sleep impacts on subsequent awake behaviors, yet the significance of their activation, or lack thereof, during REM sleep remains unclear. This review focuses on feeding-promoting cells in the lateral hypothalamus (LH) that express the vesicular GABA and glycine transporter (vgat) as a model to further understand the impact of REM sleep on neural encoding of goal-directed behavior. It emphasizes both spatial and temporal aspects of hypothalamic cell dynamics across awake behaviors and REM sleep, and discusses a role for REM sleep in brain plasticity underlying energy homeostasis and behavioral optimization.

Dim light in the evening causes coordinated realignment of circadian rhythms, sleep, and short-term memory

In modern societies, people are regularly exposed to artificial light (e.g., light-emitting electronic devices). Dim light in the evening (DLE) imposes an artificial extension of the solar day, increasing our alertness before bedtime, delaying melatonin timing and sleep onset, and increasing sleepiness in the next morning. Using laboratory mice as a model organism, we show that 2 wk of 4-h, 20-lux DLE postpones rest–activity rhythms, delays molecular rhythms in the brain and body, and reverses the diurnal pattern of short-term memory performance. These results highlight the biological impact of DLE and emphasize the need to optimize our evening light exposure if we are to avoid shifting our biological clocks.

Light provides the primary signal for entraining circadian rhythms to the day/night cycle. In addition to rods and cones, the retina contains a small population of photosensitive retinal ganglion cells (pRGCs) expressing the photopigment melanopsin (OPN4). Concerns have been raised that exposure to dim artificial lighting in the evening (DLE) may perturb circadian rhythms and sleep patterns, and OPN4 is presumed to mediate these effects. Here, we examine the effects of 4-h, 20-lux DLE on circadian physiology and behavior in mice and the role of OPN4 in these responses. We show that 2 wk of DLE induces a phase delay of ∼2 to 3 h in mice, comparable to that reported in humans. DLE-induced phase shifts are unaffected in Opn4^−/− mice, indicating that rods and cones are capable of driving these responses in the absence of melanopsin. DLE delays molecular clock rhythms in the heart, liver, adrenal gland, and dorsal hippocampus. It also reverses short-term recognition memory performance, which is associated with changes in preceding sleep history. In addition, DLE modifies patterns of hypothalamic and cortical cFos signals, a molecular correlate of recent neuronal activity. Together, our data show that DLE causes coordinated realignment of circadian rhythms, sleep patterns, and short-term memory process in mice. These effects are particularly relevant as DLE conditions―due to artificial light exposure―are experienced by the majority of the populace on a daily basis.

Chemogenetic modulation of histaminergic neurons in the tuberomamillary nucleus alters territorial aggression and wakefulness

Designer receptor activated by designer drugs (DREADDs) techniques are widely used to modulate the activities of specific neuronal populations during behavioural tasks. However, DREADDs-induced modulation of histaminergic neurons in the tuberomamillary nucleus (HA^TMN neurons) has produced inconsistent effects on the sleep–wake cycle, possibly due to the use of Hdc-Cre mice driving Cre recombinase and DREADDs activity outside the targeted region. Moreover, previous DREADDs studies have not examined locomotor activity and aggressive behaviours, which are also regulated by brain histamine levels. In the present study, we investigated the effects of HA^TMN activation and inhibition on the locomotor activity, aggressive behaviours and sleep–wake cycle of Hdc-Cre mice with minimal non-target expression of Cre-recombinase. Chemoactivation of HA^TMN moderately enhanced locomotor activity in a novel open field. Activation of HA^TMN neurons significantly enhanced aggressive behaviour in the resident–intruder test. Wakefulness was increased and non-rapid eye movement (NREM) sleep decreased for an hour by HA^TMN chemoactivation. Conversely HA^TMN chemoinhibition decreased wakefulness and increased NREM sleep for 6 h. These changes in wakefulness induced by HA^TMN modulation were related to the maintenance of vigilance state. These results indicate the influences of HA^TMN neurons on exploratory activity, territorial aggression, and wake maintenance.

GABAergic Neurons in the Dorsal-Intermediate Lateral Septum Regulate Sleep-Wakefulness and Anesthesia in Mice

BACKGROUND

The γ-aminobutyric acid-mediated (GABAergic) inhibitory system in the brain is critical for regulation of sleep-wake and general anesthesia. The lateral septum contains mainly GABAergic neurons, being cytoarchitectonically divided into the dorsal, intermediate, and ventral parts. This study hypothesized that GABAergic neurons of the lateral septum participate in the control of wakefulness and promote recovery from anesthesia.

METHODS

By employing fiber photometry, chemogenetic and optogenetic neuronal manipulations, anterograde tracing, in vivo electrophysiology, and electroencephalogram/electromyography recordings in adult male mice, the authors measured the role of lateral septum GABAergic neurons to the control of sleep-wake transition and anesthesia emergence and the corresponding neuron circuits in arousal and emergence control.

RESULTS

The GABAergic neurons of the lateral septum exhibited high activities during the awake state by in vivo fiber photometry recordings (awake vs. non-rapid eye movement sleep: 3.3 ± 1.4% vs. -1.3 ± 1.2%, P < 0.001, n = 7 mice/group; awake vs. anesthesia: 2.6 ± 1.2% vs. -1.3 ± 0.8%, P < 0.001, n = 7 mice/group). Using chemogenetic stimulation of lateral septum GABAergic neurons resulted in a 100.5% increase in wakefulness and a 51.2% reduction in non-rapid eye movement sleep. Optogenetic activation of these GABAergic neurons promoted wakefulness from sleep (median [25th, 75th percentiles]: 153.0 [115.9, 179.7] s to 4.0 [3.4, 4.6] s, P = 0.009, n = 5 mice/group) and accelerated emergence from isoflurane anesthesia (514.4 ± 122.2 s vs. 226.5 ± 53.3 s, P < 0.001, n = 8 mice/group). Furthermore, the authors demonstrated that the lateral septum GABAergic neurons send 70.7% (228 of 323 cells) of monosynaptic projections to the ventral tegmental area GABAergic neurons, preferentially inhibiting their activities and thus regulating wakefulness and isoflurane anesthesia depth.

CONCLUSIONS

The results uncover a fundamental role of the lateral septum GABAergic neurons and their circuit in maintaining awake state and promoting general anesthesia emergence time.

EDITOR’S PERSPECTIVE

Assessing the treatment of cannabidiolic acid methyl ester: a stable synthetic analogue of cannabidiolic acid on c-Fos and NeuN expression in the hypothalamus of rats

BACKGROUND

Cannabidiol (CBD), the non-psychotropic compound from Cannabis sativa, shows positive results on controlling several health disturbances; however, comparable data regarding additional chemical from C. sativa, such as cannabidiolic acid (CBDA), is scarce due to its instability. To address this limitation, a stable CBDA analogue, CBDA methyl ester (HU-580), was synthetized and showed CBDA-like effects. Recently, we described that HU-580 increased wakefulness and wake-related neurochemicals.

OBJECTIVE

To extend the comprehension of HU-580´s properties on waking, the c-Fos and NeuN expression in a wake-linked brain area, the hypothalamus was evaluated.

METHODS

c-Fos and NeuN expression in hypothalamic sections were analyzed after the injections of HU-580 (0.1 or 100 μg/kg, i.p.).

RESULTS

Systemic administrations of HU-580 increased c-Fos and neuronal nuclei (NeuN) expression in hypothalamic nuclei, including the dorsomedial hypothalamic nucleus dorsal part, dorsomedial hypothalamic nucleus compact part, and dorsomedial hypothalamic nucleus ventral part.

CONCLUSION

HU-580 increased c-Fos and NeuN immunoreactivity in hypothalamus nuclei suggesting that this drug might modulate the sleep-wake cycle by engaging the hypothalamus.

The Role of Central Neurotensin in Regulating Feeding and Body Weight

The small peptide neurotensin (Nts) is implicated in myriad processes including analgesia, thermoregulation, reward, arousal, blood pressure, and modulation of feeding and body weight. Alterations in Nts have recently been described in individuals with obesity or eating disorders, suggesting that disrupted Nts signaling may contribute to body weight disturbance. Curiously, Nts mediates seemingly opposing regulation of body weight via different tissues. Peripherally acting Nts promotes fat absorption and weight gain, whereas central Nts signaling suppresses feeding and weight gain. Thus, because Nts is pleiotropic, a location-based approach must be used to understand its contributions to disordered body weight and whether the Nts system might be leveraged to improve metabolic health. Here we review the role of Nts signaling in the brain to understand the sites, receptors, and mechanisms by which Nts can promote behaviors that modify body weight. New techniques permitting site-specific modulation of Nts and Nts receptor-expressing cells suggest that, even in the brain, not all Nts circuitry exerts the same function. Intriguingly, there may be dedicated brain regions and circuits via which Nts specifically suppresses feeding behavior and weight gain vs other Nts-attributed physiology. Defining the central mechanisms by which Nts signaling modifies body weight may suggest strategies to correct disrupted energy balance, as needed to address overweight, obesity, and eating disorders.

Two waves of transcriptomic changes in periovulatory human granulosa cells

STUDY QUESTION

How does the human granulosa cell (GC) transcriptome change during ovulation?

SUMMARY ANSWER

Two transcriptional peaks were observed at 12 h and at 36 h after induction of ovulation, both dominated by genes and pathways known from the inflammatory system.

WHAT IS KNOWN ALREADY

The crosstalk between GCs and the oocyte, which is essential for ovulation and oocyte maturation, can be assessed through transcriptomic profiling of GCs. Detailed transcriptional changes during ovulation have not previously been assessed in humans.

STUDY DESIGN, SIZE, DURATION

This prospective cohort study comprised 50 women undergoing fertility treatment in a standard antagonist protocol at a university hospital-affiliated fertility clinic in 2016-2018.

PARTICIPANTS/MATERIALS, SETTING, METHODS

From each woman, one sample of GCs was collected by transvaginal ultrasound-guided follicle aspiration either before or 12 h, 17 h or 32 h after ovulation induction (OI). A second sample was collected at oocyte retrieval, 36 h after OI. Total RNA was isolated from GCs and analyzed by microarray. Gene expression differences between the five time points were assessed by ANOVA with a random factor accounting for the pairing of samples, and seven clusters of protein-coding genes representing distinct expression profiles were identified. These were used as input for subsequent bioinformatic analyses to identify enriched pathways and suggest upstream regulators. Subsets of genes were assessed to explore specific ovulatory functions.

MAIN RESULTS AND THE ROLE OF CHANCE

We identified 13 345 differentially expressed transcripts across the five time points (false discovery rate, <0.01) of which 58% were protein-coding genes. Two clusters of mainly downregulated genes represented cell cycle pathways and DNA repair. Upregulated genes showed one peak at 12 h that resembled the initiation of an inflammatory response, and one peak at 36 h that resembled the effector functions of inflammation such as vasodilation, angiogenesis, coagulation, chemotaxis and tissue remodelling. Genes involved in cell-matrix interactions as a part of cytoskeletal rearrangement and cell motility were also upregulated at 36 h. Predicted activated upstream regulators of ovulation included FSH, LH, transforming growth factor B1, tumour necrosis factor, nuclear factor kappa-light-chain-enhancer of activated B cells, coagulation factor 2, fibroblast growth factor 2, interleukin 1 and cortisol, among others. The results confirmed early regulation of several previously described factors in a cascade inducing meiotic resumption and suggested new factors involved in cumulus expansion and follicle rupture through co-regulation with previously described factors.

LARGE SCALE DATA

The microarray data were deposited to the Gene Expression Omnibus (www.ncbi.nlm.nih.gov/gds/, accession number: GSE133868).

LIMITATIONS, REASONS FOR CAUTION

The study included women undergoing ovarian stimulation and the findings may therefore differ from a natural cycle. However, the results confirm significant regulation of many well-established ovulatory genes from a series of previous studies such as amphiregulin, epiregulin, tumour necrosis factor alfa induced protein 6, tissue inhibitor of metallopeptidases 1 and plasminogen activator inhibitor 1, which support the relevance of the results.

WIDER IMPLICATIONS OF THE FINDINGS

The study increases our understanding of human ovarian function during ovulation, and the publicly available dataset is a valuable resource for future investigations. Suggested upstream regulators and highly differentially expressed genes may be potential pharmaceutical targets in fertility treatment and gynaecology.

STUDY FUNDING/COMPETING INTEREST(S)

The study was funded by EU Interreg ÔKS V through ReproUnion (www.reprounion.eu) and by a grant from the Region Zealand Research Foundation. None of the authors have any conflicts of interest to declare.

Central Neural Circuits Orchestrating Thermogenesis, Sleep-Wakefulness States and General Anesthesia States

Great progress has been made in specifically identifying the central neural circuits (CNCs) of the core body temperature (Tcore), sleep-wakefulness states (SWs), and general anesthesia states (GAs), mainly utilizing optogenetic or chemogenetic manipulations. We summarize the neuronal populations and neural pathways of these three CNCs, which gives evidence for the orchestration within these three CNCs, and the integrative regulation of these three CNCs by different environmental light signals. We also outline some transient receptor potential (TRP) channels that function in the CNCs-Tcore and are modulated by some general anesthetics, which makes TRP channels possible targets for addressing the general-anesthetics-induced-hypothermia (GAIH). We suggest this review will provide new orientations for further consummating these CNCs and elucidating the central mechanisms of GAIH.

Sleep-Wake Control by Melanin-Concentrating Hormone (MCH) Neurons: a Review of Recent Findings

PURPOSE OF THE REVIEW

Melanin-concentrating hormone (MCH)-expressing neurons located in the lateral hypothalamus are considered as an integral component of sleep-wake circuitry. However, the precise role of MCH neurons in sleep-wake regulation has remained unclear, despite several years of research employing a wide range of techniques. We review recent data on this aspect, which are mostly inconsistent, and propose a novel role for MCH neurons in sleep regulation.

RECENT FINDINGS

While almost all studies using "gain-of-function" approaches show an increase in rapid eye movement sleep (or paradoxical sleep; PS), loss-of-function approaches have not shown reductions in PS. Similarly, the reported changes in wakefulness or non-rapid eye movement sleep (slow-wave sleep; SWS) with manipulation of the MCH system using conditional genetic methods are inconsistent. Currently available data do not support a role for MCH neurons in spontaneous sleep-wake but imply a crucial role for them in orchestrating sleep-wake responses to changes in external and internal environments.

Hypothalamic circuitry underlying stress-induced insomnia and peripheral immunosuppression

The neural substrates of insomnia/hyperarousal induced by stress remain unknown. Here, we show that restraint stress leads to hyperarousal associated with strong activation of corticotropin-releasing hormone neurons in the paraventricular nucleus of hypothalamus (CRH^PVN) and hypocretin neurons in the lateral hypothalamus (Hcrt^LH). CRH^PVN neurons directly innervate Hcrt^LH neurons, and optogenetic stimulation of LH-projecting CRH^PVN neurons elicits hyperarousal. CRISPR-Cas9-mediated knockdown of the crh gene in CRH^PVN neurons abolishes hyperarousal induced by stimulating LH-projecting CRH^PVN neurons. Genetic ablation of Hcrt neurons or crh gene knockdown significantly counteracts restraint stress-induced hyperarousal. Single-cell mass cytometry by time of flight (CyTOF) revealed extensive changes to immune cell distribution and functional responses in peripheral blood during hyperarousal upon optogenetic stimulation of CRH^PVN neurons simulating stress-induced insomnia. Our findings suggest both central and peripheral systems are synergistically engaged in the response to stress via CRH^PVN circuitry.

Cellular and molecular properties of neural progenitors in the developing mammalian hypothalamus

The neuroendocrine hypothalamus is the central regulator of vital physiological homeostasis and behavior. However, the cellular and molecular properties of hypothalamic neural progenitors remain unexplored. Here, hypothalamic radial glial (hRG) and hypothalamic mantle zone radial glial (hmRG) cells are found to be neural progenitors in the developing mammalian hypothalamus. The hmRG cells originate from hRG cells and produce neurons. During the early development of hypothalamus, neurogenesis occurs in radial columns and is initiated from hRG cells. The radial glial fibers are oriented toward the locations of hypothalamic subregions which act as a scaffold for neuronal migration. Furthermore, we use single-cell RNA sequencing to reveal progenitor subtypes in human developing hypothalamus and characterize specific progenitor genes, such as TTYH1, HMGA2, and FAM107A. We also demonstrate that HMGA2 is involved in E2F1 pathway, regulating the proliferation of progenitor cells by targeting on the downstream MYBL2. Different neuronal subtypes start to differentiate and express specific genes of hypothalamic nucleus at gestational week 10. Finally, we reveal the developmental conservation of nuclear structures and marker genes in mouse and human hypothalamus. Our identification of cellular and molecular properties of neural progenitors provides a basic understanding of neurogenesis and regional formation of the non-laminated hypothalamus.

Basal Forebrain Parvalbumin Neurons Mediate Arousals from Sleep Induced by Hypercarbia or Auditory Stimuli

The ability to rapidly arouse from sleep is important for survival. However, increased arousals in patients with sleep apnea and other disorders prevent restful sleep and contribute to cognitive, metabolic, and physiologic dysfunction [1, 2]. Little is currently known about which neural systems mediate these brief arousals, hindering the development of treatments that restore normal sleep. The basal forebrain (BF) receives inputs from many nuclei of the ascending arousal system, including the brainstem parabrachial neurons, which promote arousal in response to elevated blood carbon dioxide levels, as seen in sleep apnea [3]. Optical inhibition of the terminals of parabrachial neurons in the BF impairs cortical arousals to hypercarbia [4], but which BF cell types mediate cortical arousals in response to hypercarbia or other sensory stimuli is unknown. Here, we tested the role of BF parvalbumin (PV) neurons in arousal using optogenetic techniques in mice. Optical stimulation of BF-PV neurons produced rapid transitions to wakefulness from non-rapid eye movement (NREM) sleep but did not affect REM-wakefulness transitions. Unlike previous studies of BF glutamatergic and cholinergic neurons, arousals induced by stimulation of BF-PV neurons were brief and only slightly increased total wake time, reminiscent of clinical findings in sleep apnea [5, 6]. Bilateral optical inhibition of BF-PV neurons increased the latency to arousal produced by exposure to hypercarbia or auditory stimuli. Thus, BF-PV neurons are an important component of the brain circuitry that generates brief arousals from sleep in response to stimuli, which may indicate physiological dysfunction or danger to the organism.

The Lateral Hypothalamus: An Uncharted Territory for Processing Peripheral Neurogenic Inflammation

The roles of the hypothalamus and particularly the lateral hypothalamus (LH) in the regulation of inflammation and pain have been widely studied. The LH consists of a parasympathetic area that has connections with all the major parts of the brain. It controls the autonomic nervous system (ANS), regulates feeding behavior and wakeful cycles, and is a part of the reward system. In addition, it contains different types of neurons, most importantly the orexin neurons. These neurons, though few in number, perform critical functions such as inhibiting pain transmission and interfering with the reward system, feeding behavior and the hypothalamic pituitary axis (HPA). Recent evidence has identified a new role for orexin neurons in the modulation of pain transmission associated with several inflammatory diseases, including rheumatoid arthritis and ulcerative colitis. Here, we review recent findings on the various physiological functions of the LH with special emphasis on the orexin/receptor system and its role in mediating inflammatory pain.

Neurotensin in reward processes

Neurotensin (NTS) is a neuropeptide neurotransmitter expressed in the central and peripheral nervous systems. Many studies over the years have revealed a number of roles for this neuropeptide in body temperature regulation, feeding, analgesia, ethanol sensitivity, psychosis, substance use, and pain. This review provides a general survey of the role of neurotensin with a focus on modalities that we believe to be particularly relevant to the study of reward. We focus on NTS signaling in the ventral tegmental area, nucleus accumbens, lateral hypothalamus, bed nucleus of the stria terminalis, and central amygdala. Studies on the role of NTS outside of the ventral tegmental area are still in their relative infancy, yet they reveal a complex role for neurotensinergic signaling in reward-related behaviors that merits further study. This article is part of the special issue on 'Neuropeptides'.

The hypocretin (orexin) system: from a neural circuitry perspective

Hypocretin/orexin neurons are distributed restrictively in the hypothalamus, a brain region known to orchestrate diverse functions including sleep, reward processing, food intake, thermogenesis, and mood. Since the hypocretins/orexins were discovered more than two decades ago, extensive studies have accumulated concrete evidence showing the pivotal role of hypocretin/orexin in diverse neural modulation. New method of viral-mediated tracing system offers the possibility to map the monosynaptic inputs and detailed anatomical connectivity of Hcrt neurons. With the development of powerful research techniques including optogenetics, fiber-photometry, cell-type/pathway specific manipulation and neuronal activity monitoring, as well as single-cell RNA sequencing, the details of how hypocretinergic system execute functional modulation of various behaviors are coming to light. In this review, we focus on the function of neural pathways from hypocretin neurons to target brain regions. Anatomical and functional inputs to hypocretin neurons are also discussed. We further briefly summarize the development of pharmaceutical compounds targeting hypocretin signaling. This article is part of the special issue on Neuropeptides.

A subpopulation of Bdnf-e1-expressing glutamatergic neurons in the lateral hypothalamus critical for thermogenesis control

Objective

Brown adipose tissue (BAT)–mediated thermogenesis plays a key role in energy homeostasis and the maintenance of body temperature. Previous work suggests that brain-derived neurotrophic factor (BDNF) is involved in BAT thermogenesis, but the underlying neural circuits and molecular mechanism remain largely unknown. This is in part due to the difficulties in manipulating BDNF expression in different brain regions through different promoters and the lack of tools to identify neurons in the brain specifically involved in BAT thermogenesis.

Methods

We have created several lines of mutant mice in which BDNF transcription from a specific promoter was selectively disrupted by replacing Bdnf with green fluorescent protein (GFP; Bdnf-e1, -e4, and -e6^−/− mice). As such, cells expressing Bdnf-e1, -e4, or -e6 were labeled with GFP. To identify BAT-connected thermogenesis neurons in brain, we applied the retrograde pseudorabies virus labeling method from BAT. We also used chemogenetic tools to manipulate specific neurons coupled with BAT temperature recording. Moreover, we developed a new TrkB agonist antibody to rescue the BAT thermogenesis deficits.

Results

We show that selective disruption of Bdnf expression from promoter 1 (Bdnf-e1) resulted in severe obesity and deficits of BAT-mediated thermogenesis. Body temperature response to cold was impaired in Bdnf-e1^−/− mice. BAT expression of Ucp1 and Pcg1a, genes known to regulate thermogenesis, was also reduced, accompanying a decrease in the sympathetic activity of BAT. Staining of cells expressing Bdnf-e1 transcript, combined with transsynaptic, retrograde-tracing labeling of BAT-connected neurons, identified a group of excitatory neurons in lateral hypothalamus (LH) critical for thermogenesis regulation. Moreover, an adaptive thermogenesis defect in Bdnf-e1^−/− mice was rescued by injecting an agonistic antibody for TrkB, the BDNF receptor, into LH. Remarkably, activation of the excitatory neurons (VGLUT2+) in LH through chemogenetic tools resulted in a rise of BAT temperature.

Conclusions

These results reveal a specific role of BDNF promoter I in thermogenesis regulation and define a small subset of neurons in LH that contribute to such regulation.

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Only Bdnf-e1^−/−, but not Bdnf-e4^−/− or Bdnf-e6^−/−, mutant mice exhibited deficiencies of BAT thermogenesis.

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Neurons that are both Bdnf-e1 expressing and BAT-connected were found only in LH.

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BAT-connected neurons in LH are glutamatergic.

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Activation of the LH glutamatergic neurons resulted in an increase in BAT temperature.

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Administration of TrkB agonist antibody in LH rescued thermogenesis deficits.

Control of Non-REM Sleep by Midbrain Neurotensinergic Neurons

The periaqueductal gray (PAG) in the midbrain is known to coordinate behavioral and autonomic responses to threat and injury through its descending projections to the brainstem. Here, we show that neurotensin (NTS)-expressing glutamatergic neurons in the ventrolateral PAG (vlPAG) powerfully promote non-rapid eye movement (NREM) sleep partly through their projection to the caudal medulla. Optogenetic and chemogenetic activation of vlPAG NTS neurons strongly enhanced NREM sleep, whereas their inactivation increased wakefulness. Calcium imaging and optrode recording showed that they are preferentially active during NREM sleep. The NREM-promoting effect of vlPAG NTS neurons is partly mediated by their projection to the caudal ventromedial medulla, where they excite GABAergic neurons. Bidirectional optogenetic and chemogenetic manipulations showed that the medullary GABAergic neurons also promote NREM sleep, and they innervate multiple monoaminergic populations. Together, these findings reveal a novel pathway for NREM sleep generation, in which glutamatergic neurons drive broad GABAergic inhibition of wake-promoting neuronal populations.

[Not Available]

Neurotensin (Nts) is a neuropeptide implicated in the regulation of many facets of physiology, including cardiovascular tone, pain processing, ingestive behaviors, locomotor drive, sleep, addiction and social behaviors. Yet, there is incomplete understanding about how the various populations of Nts neurons distributed throughout the brain mediate such physiology. This knowledge gap largely stemmed from the inability to simultaneously identify Nts cell bodies and manipulate them in vivo. One means of overcoming this obstacle is to study Nts^Cre mice crossed onto a Cre-inducible green fluorescent reporter line (Nts^Cre;GFP mice), as these mice permit both visualization and in vivo modulation of specific populations of Nts neurons (using Cre-inducible viral and genetic tools) to reveal their function. Here we provide a comprehensive characterization of the distribution and relative densities of the Nts-GFP populations observed throughout the male Nts^Cre;GFP mouse brain, which will pave the way for future work to define their physiologic roles. We also compared the distribution of Nts-GFP neurons with Nts-In situ Hybridization (Nts-ISH) data from the adult mouse brain. By comparing these data sets we can distinguish Nts-GFP populations that may only transiently express Nts during development but not in the mature brain, and hence which populations may not be amenable to Cre-mediated manipulation in adult Nts^Cre;GFP mice. This atlas of Nts-GFP neurons will facilitate future studies using the Nts^Cre;GFP line to describe the physiological functions of individual Nts populations and how modulating them may be useful to treat disease.