Organization of axonal projections from the anterolateral area of the bed nuclei of the stria terminalis

VGluT3 BNST neurons transmit GABA and restrict feeding without affecting rewarding or aversive processing

The bed nucleus of the stria terminalis (BNST) is involved in feeding, reward, aversion, and anxiety-like behavior. We identify BNST neurons defined by the expression of vesicular glutamate transporter 3, VGluT3. VGluT3 neurons were localized to anteromedial BNST, were molecularly distinct from accumbal VGluT3 neurons, and co-express vesicular GABA transporter (VGaT). Cell-type specific presynaptic processes were identified in arcuate nucleus (ARC) and the paraventricular nucleus of the hypothalamus (PVN), regions critical for feeding and homeostatic regulation. Whole-cell patch-clamp electrophysiology revealed that, while these neurons co-express VGluT3 and VGaT, they functionally transmit GABA to both ARC and PVN, with rare glutamate co-transmission to ARC. Neuronal recordings of VGluT3 BNST neurons showed greater calcium-dependent signaling in response to sucrose consumption while sated compared with fasted. When fasted, optogenetic stimulation of BNST VGluT3 neurons decreased sucrose consumption using several stimulation conditions but not when stimulation occurred prior to sucrose access, suggesting that BNST VGluT3 activation concurrent with consumption in the fasted state reduces feeding. BNST VGluT3 activation during anxiety-like paradigms (novelty-suppressed feeding, open field, and elevated zero maze) and real-time place conditioning resulted in no changes in anxiety-like or reward/aversion behavior. We interpret these data such that VGluT3 BNST neurons represent a unique cellular population within the BNST that provides inhibitory input to hypothalamic regions to decrease feeding without affecting anxiety-like or reward/aversion behavior.

The Neurobehavioral State hypothesis

Since the early attempts to understand the brain made by Greek philosophers more than 2000 years ago, one of the main questions in neuroscience has been how the brain perceives all the stimuli in the environment and uses this information to implement a response. Recent hypotheses of the neural code rely on the existence of an ideal observer, whether on specific areas of the cerebral cortex or distributed network composed of cortical and subcortical elements. The Neurobehavioral State hypothesis stipulates that neurons are in a quasi-stable state due to the dynamic interaction of their molecular components. This increases their computational capabilities and electrophysiological behavior further than a binary active/inactive state. Together, neuronal populations across the brain learn to identify and associate internal and external stimuli with actions and emotions. Furthermore, such associations can be stored through the regulation of neuronal components as new quasi-stable states. Using this framework, behavior arises as the result of the dynamic interaction between internal and external stimuli together with previously established quasi-stable states that delineate the behavioral response. Finally, the Neurobehavioral State hypothesis is firmly grounded on present evidence of the complex dynamics within the brain, from the molecular to the network level, and avoids the need for a central observer by proposing the brain configures itself through experience-driven associations.

The regulative role and mechanism of BNST in anxiety disorder

Anxiety disorders, common yet impactful emotional disturbances, significantly affect physical and mental health globally. Many neuron circuits are associated with anxiety regulation like septo-hippocampal loop, amygdala(AMYG), bed nucleus of the stria terminalis (BNST), ventral hippocampus (vHPC), and brain regions like medial prefrontal cortex (mPFC). However, the concrete mechanism of anxiety disorder in BNST is relatively unknown. Recent research showed BNST plays a critical role in modulating anxiety owing to its anatomical location and special circuit characteristics, which are considered to be a hub in the limbic system regulating anxiety. BNST consists with multiple subregions, which can project separately into different brain regions and exert projecting independently to various brain regions with distinct regulatory effects. Moreover, multiple signal pathways in BNST are reported to play significant roles in regulating anxiety and stress behavior. This review briefly describes anxiety disorders and subdivisions and functions of BNST, focusing on the main neural circuits that serve as fundamental pathways in both the genesis and potential treatment of anxiety disorders and the molecular mechanism of BNST on anxiety. The complexity of structures and mechanisms has facilitated the development of imaging techniques. Innovative multimodal imaging techniques, such as functional magnetic resonance imaging (fMRI) and positron emission tomography (PET), have non-invasively illuminated BNST activities and their functional connections with other brain areas. These methodologies provide a deeper understanding of how BNST responds to anxiety-inducing stimuli, offering invaluable insights into its complex role in anxiety regulation. The continued exploration of BNST in anxiety research promises not only to elucidate fundamental neurobiological mechanisms but also to foster advancements in clinical treatments for anxiety disorders.

Sex and sobriety: Human brain structure and function in AUD abstinence

Women are drinking alcohol as much as men for the first time in history. Women experience more health-related consequences from alcohol use disorder (AUD), like increased prevalence of alcohol-related cancers, faster progression of alcohol-related liver disease, and greater risk for relapse compared to men. Thus, sex differences in chronic alcohol use pose a substantial public health problem. Despite these evident sex differences, our understanding of how these differences present during alcohol abstinence is limited. Investigations of brain structure and function are therefore critical for disentangling factors that lead to sex differences in AUD abstinence. This review will discuss current human neuroimaging data on sex differences in alcohol abstinence, focusing on structural and functional brain measures. Current structural imaging literature reveals that abstinent men have smaller gray and white matter volume and weaker structural connectivity compared to control men. Interestingly, abstinent women do not show differences in brain structure when compared to controls; instead, abstinent women show a relation between alcohol use and decreased measures of brain structure. Current functional brain studies reveal that abstinent men exhibit greater brain activation and stronger task-based functional connectivity to aversive stimuli than control men, while abstinent women exhibit lesser brain activation and weaker task-based functional connectivity than control women. Together, the current literature suggests that sex differences persist well into alcohol abstinence and impact brain structure and function differently. Understanding how men and women differ during alcohol abstinence can improve our understanding of sex-specific effects of alcohol, which will be critical to augment treatment methods to better serve women.

Estrous Cycle-Dependent Modulation of Sexual Receptivity in Female Mice by Estrogen Receptor Beta-Expressing Cells in the Dorsal Raphe Nucleus

The sexual receptivity of female mice, shown as lordosis response, is mainly regulated by estradiol action on estrogen receptor alpha (ERα) and beta (ERβ), depending on the day of the estrous cycle. Previous studies revealed that ERα in the ventromedial nucleus of the hypothalamus (VMH) plays an essential role in the induction of lordosis on the day of estrus (Day 1). However, the mechanisms of the transition to nonreceptive states on the day after estrus (Day 2) are not completely understood. In the present study, we investigated the possible role of ERβ, which is highly expressed in the dorsal raphe nucleus (DRN), in lordosis expression. We found that ERβ-Cre female mice, which were ovariectomized and primed with estradiol and progesterone to mimic the estrous cycle, showed high levels of lordosis on Day 2 when ERβ-expressing DRN (DRN-ERβ+) neuronal activity was chemogenetically suppressed. This finding suggests that excitation of DRN-ERβ+ neurons is necessary for the decline of lordosis on Day 2. Fiber photometry recordings during female-male behavioral interactions revealed that DRN-ERβ+ neuronal activation in response to male intromission was significantly more prolonged on Day 2 compared with Day 1. Chemogenetic overstimulation of DRN-ERβ+ neurons induced c-Fos expression in brain areas known to be inhibitory for lordosis expression, even though they did not express anterogradely labeled fibers of DRN-ERβ+ cells. These findings collectively suggest that DRN-ERβ+ neuronal excitation serves as an inhibitory modulator and is responsible for the decline in receptivity during nonestrus phases.

Whole brain alignment of spatial transcriptomics between humans and mice with BrainAlign

The increasing utilization of mouse models in human neuroscience research places higher demands on computational methods to translate findings from the mouse brain to the human one. In this study, we develop BrainAlign, a self-supervised learning approach, for the whole brain alignment of spatial transcriptomics (ST) between humans and mice. BrainAlign encodes spots and genes simultaneously in two separated shared embedding spaces by a heterogeneous graph neural network. We demonstrate that BrainAlign could integrate cross-species spots into the embedding space and reveal the conserved brain regions supported by ST information, which facilitates the detection of homologous regions between humans and mice. Genomic analysis further presents gene expression connections between humans and mice and reveals similar expression patterns for marker genes. Moreover, BrainAlign can accurately map spatially similar homologous regions or clusters onto a unified spatial structural domain while preserving their relative positions.

Chronic alcohol consumption alters sex-dependent BNST neuron function in rhesus macaques

Repeated alcohol drinking contributes to a number of neuropsychiatric diseases, including alcohol use disorder and co-expressed anxiety and mood disorders. Women are more susceptible to the development and expression of these diseases with the same history of alcohol exposure as men, suggesting they may be more sensitive to alcohol-induced plasticity in limbic brain regions controlling alcohol drinking, stress responsivity, and reward processing, among other behaviors. Using a translational model of alcohol drinking in rhesus monkeys, we examined sex differences in the basal function and plasticity of neurons in the bed nucleus of the stria terminalis (BNST), a brain region in the extended amygdala shown to be a hub circuit node dysregulated in individuals with anxiety and alcohol use disorder. We performed slice electrophysiology recordings from BNST neurons in male and female monkeys following daily "open access" (22 h/day) to 4% ethanol and water for more than one year or control conditions. We found that BNST neurons from control females had reduced overall current density, hyperpolarization-activated depolarizing current (Ih), and inward rectification, as well as higher membrane resistance and greater synaptic glutamatergic release and excitatory drive, than those from control males, suggesting that female BNST neurons are more basally excited than those from males. Chronic alcohol drinking produced a shift in these measures in both sexes, decreasing current density, Ih, and inward rectification and increasing synaptic excitation. In addition, network activity-dependent synaptic inhibition was basally higher in BNST neurons of males than females, and alcohol exposure increased this in both sexes, a putative homeostatic mechanism to counter hyperexcitability. Altogether, these results suggest that the rhesus BNST is more basally excited in females than males and chronic alcohol drinking produces an overall increase in excitability and synaptic excitation. These results shed light on the mechanisms contributing to the female-biased susceptibility to neuropsychiatric diseases including co-expressed anxiety and alcohol use disorder.

Synergism between two BLA-to-BNST pathways for appropriate expression of anxiety-like behaviors in male mice

Understanding how distinct functional circuits are coordinated to fine-tune mood and behavior is of fundamental importance. Here, we observe that within the dense projections from basolateral amygdala (BLA) to bed nucleus of stria terminalis (BNST), there are two functionally opposing pathways orchestrated to enable contextually appropriate expression of anxiety-like behaviors in male mice. Specifically, the anterior BLA neurons predominantly innervate the anterodorsal BNST (adBNST), while their posterior counterparts send massive fibers to oval BNST (ovBNST) with moderate to adBNST. Optogenetic activation of the anterior and posterior BLA inputs oppositely regulated the activity of adBNST neurons and anxiety-like behaviors, via disengaging and engaging the inhibitory ovBNST-to-adBNST microcircuit, respectively. Importantly, the two pathways exhibited synchronized but opposite responses to both anxiolytic and anxiogenic stimuli, partially due to their mutual inhibition within BLA and the different inputs they receive. These findings reveal synergistic interactions between two BLA-to-BNST pathways for appropriate anxiety expression with ongoing environmental demands.

Chronic alcohol consumption alters sex-dependent BNST neuron function in rhesus macaques

Repeated alcohol drinking contributes to a number of neuropsychiatric diseases, including alcohol use disorder and co-expressed anxiety and mood disorders. Women are more susceptible to the development and expression of these diseases with the same history of alcohol exposure as men, suggesting they may be more sensitive to alcohol-induced plasticity in limbic brain regions controlling alcohol drinking, stress responsivity, and reward processing, among other behaviors. Using a translational model of alcohol drinking in rhesus monkeys, we examined sex differences in the basal function and plasticity of neurons in the bed nucleus of the stria terminalis (BNST), a brain region in the extended amygdala shown to be a hub circuit node dysregulated in individuals with anxiety and alcohol use disorder. We performed slice electrophysiology recordings from BNST neurons in male and female monkeys following daily "open access" (22 hr/day) to 4% ethanol and water for more than one year or control conditions. We found that BNST neurons from control females had reduced overall current density, hyperpolarization-activated depolarizing current (Ih), and inward rectification, as well as higher membrane resistance and greater synaptic glutamatergic release and excitatory drive, than those from control males, suggesting that female BNST neurons are more basally excited than those from males. Chronic alcohol drinking produced a shift in these measures in both sexes, decreasing current density, Ih, and inward rectification and increasing synaptic excitation. In addition, network activity-dependent synaptic inhibition was basally higher in BNST neurons of males than females, and alcohol exposure increased this in both sexes, a putative homeostatic mechanism to counter hyperexcitability. Altogether, these results suggest that the rhesus BNST is more basally excited in females than males and chronic alcohol drinking produces an overall increase in excitability and synaptic excitation. These results shed light on the mechanisms contributing to the female-biased susceptibility to neuropsychiatric diseases including co-expressed anxiety and alcohol use disorder.

Parental brain through time: The origin and development of the neural circuit of mammalian parenting

This review consolidates current knowledge on mammalian parental care, focusing on its neural mechanisms, evolutionary origins, and derivatives. Neurobiological studies have identified specific neurons in the medial preoptic area as crucial for parental care. Unexpectedly, these neurons are characterized by the expression of molecules signaling satiety, such as calcitonin receptor and BRS3, and overlap with neurons involved in the reproductive behaviors of males but not females. A synthesis of comparative ecology and paleontology suggests an evolutionary scenario for mammalian parental care, possibly stemming from male-biased guarding of offspring in basal vertebrates. The terrestrial transition of tetrapods led to prolonged egg retention in females and the emergence of amniotes, skewing care toward females. The nocturnal adaptation of Mesozoic mammalian ancestors reinforced maternal care for lactation and thermal regulation via endothermy, potentially introducing metabolic gate control in parenting neurons. The established maternal care may have served as the precursor for paternal and cooperative care in mammals and also fostered the development of group living, which may have further contributed to the emergence of empathy and altruism. These evolution-informed working hypotheses require empirical validation, yet they offer promising avenues to investigate the neural underpinnings of mammalian social behaviors.

Peri-ictal activation of dorsomedial dorsal raphe serotonin neurons reduces mortality associated with maximal electroshock seizures

Over one-third of patients with epilepsy will develop refractory epilepsy and continue to experience seizures despite medical treatment. These patients are at the greatest risk for sudden unexpected death in epilepsy. The precise mechanisms underlying sudden unexpected death in epilepsy are unknown, but cardiorespiratory dysfunction and arousal impairment have been implicated. Substantial circumstantial evidence suggests serotonin is relevant to sudden unexpected death in epilepsy as it modulates sleep/wake regulation, breathing and arousal. The dorsal raphe nucleus is a major serotonergic center and a component of the ascending arousal system. Seizures disrupt the firing of dorsal raphe neurons, which may contribute to reduced responsiveness. However, the relevance of the dorsal raphe nucleus and its subnuclei to sudden unexpected death in epilepsy remains unclear. The dorsomedial dorsal raphe may be a salient target due to its role in stress and its connections with structures implicated in sudden unexpected death in epilepsy. We hypothesized that optogenetic activation of dorsomedial dorsal raphe serotonin neurons in TPH2-ChR2-YFP (n = 26) mice and wild-type (n = 27) littermates before induction of a maximal electroshock seizure would reduce mortality. In this study, pre-seizure activation of dorsal raphe nucleus serotonin neurons reduced mortality in TPH2-ChR2-YFP mice with implants aimed at the dorsomedial dorsal raphe. These results implicate the dorsomedial dorsal raphe in this novel circuit influencing seizure-induced mortality. It is our hope that these results and future experiments will define circuit mechanisms that could ultimately reduce sudden unexpected death in epilepsy.

Manual segmentation of the paraventricular nucleus of the hypothalamus and the dorsal and ventral bed nucleus of stria terminalis using multimodal 7 Tesla structural MRI: probabilistic atlases for a stress-control triad

The paraventricular nucleus of the hypothalamus (PVN) is uniquely capable of proximal control over autonomic and neuroendocrine stress responses, and the bed nucleus of the stria terminalis (BNST) directly modulates PVN function, as well as playing an important role in stress control itself. The dorsal BNST (dBNST) is predominantly preautonomic, while the ventral BNST (vBNST) is predominantly viscerosensory, receiving dense noradrenergic signaling. Distinguishing the dBNST and vBNST, along with the PVN, may facilitate our understanding of dynamic interactions among these regions. T1-weighted MPRAGE and high resolution gradient echo (GRE) modalities were acquired at 7T. GRE was coregistered to MPRAGE and segmentations were performed in MRIcroGL based on their Atlas of the Human Brain depictions. The dBNST, vBNST and PVN were manually segmented in 25 participants; 10 images were rated by 2 raters. These segmentations were normalized and probabilistic atlases for each region were generated in MNI space, now available as resources for future research. We found moderate-high inter-rater reliability [n = 10; Mean Dice (SD); PVN = 0.69 (0.04); dBNST = 0.77 (0.04); vBNST = 0.62 (0.04)]. Probabilistic atlases were reverse normalized into native space for six additional participants that were segmented but not included in the original 25. We also found moderate to moderate-high reliability between the probabilistic atlases and manual segmentations [n = 6; Mean Dice (SD); PVN = 0.55 (0.12); dBNST = 0.60 (0.10); vBNST = 0.47 (0.12 SD)]. By isolating these hypothalamic and BNST subregions using ultra-high field MRI modalities, more specific delineations of these regions can facilitate greater understanding of mechanisms underlying stress-related function and psychopathology.

Chemogenetic activation of corticotropin-releasing factor-expressing neurons in the anterior bed nucleus of the stria terminalis reduces effortful motivation behaviors

Corticotropin-releasing factor (CRF) in the anterior bed nucleus of the stria terminalis (aBNST) is associated with chronic stress and avoidance behavior. However, CRF + BNST neurons project to reward- and motivation-related brain regions, suggesting a potential role in motivated behavior. We used chemogenetics to selectively activate CRF+ aBNST neurons in male and female CRF-ires-Cre mice during an effort-related choice task and a concurrent choice task. In both tasks, mice were given the option either to exert effort for high value rewards or to choose freely available low value rewards. Acute chemogenetic activation of CRF+ aBNST neurons reduced barrier climbing for a high value reward in the effort-related choice task in both males and females. Furthermore, acute chemogenetic activation of CRF+ aBNST neurons also reduced effortful lever pressing in high-performing males in the concurrent choice task. These data suggest a novel role for CRF+ aBNST neurons in effort-based decision and motivation behaviors.

Long-lasting mechanical hypersensitivity and CRF receptor type-1 neuron activation in the BNST following adolescent ethanol exposure

BACKGROUND

Adolescent alcohol use can produce long-lasting alterations in brain function, potentially leading to adverse health outcomes in adulthood. Emerging evidence suggests that chronic alcohol use can increase pain sensitivity or exacerbate existing pain conditions, but the potential neural mechanisms underlying these effects require further investigation. Here, we evaluate the impact of chronic ethanol vapor on mechanical sensitivity over the course of acute and protracted withdrawal in adolescent and adult male and female mice, and its potential association with alterations in corticotropin-releasing factor (CRF) signaling within the bed nucleus of the stria terminalis (BNST).

METHODS

Adolescent and adult male and female mice underwent intermittent ethanol vapor exposure on 4 days/week for 2 weeks. Mechanical thresholds were evaluated 5 h and 7, 14, 21, and 28 d after cessation of ethanol exposure using the von Frey test. For mice with a history of adolescent ethanol exposure, brains were collected for in situ RNAscope processing after the final test. Messenger RNA expression of c-Fos, Crfr1, and Crf in the BNST subregions was examined.

RESULTS

Exposure to intermittent ethanol vapor induced persistent mechanical hypersensitivity during withdrawal in both adolescent and adult mice. Notably, the effect was more transient in mice exposed to ethanol during adulthood, resolving by day 28 after ethanol exposure. Furthermore, both male and female mice with a history of adolescent ethanol exposure exhibited increased activation of CRF receptor type 1 (CRFR1) neurons within the dorsolateral BNST.

CONCLUSIONS

Our results support the conclusion that intermittent ethanol exposure can induce mechanical hypersensitivity, potentially through the activation of BNST CRFR1 neurons. These findings provide a basis for future studies aimed at evaluating specific subpopulations of BNST neurons and their contribution to pain in individuals with a history of alcohol use.

Emotion in action: When emotions meet motor circuits

The brain is a remarkably complex organ responsible for a wide range of functions, including the modulation of emotional states and movement. Neuronal circuits are believed to play a crucial role in integrating sensory, cognitive, and emotional information to ultimately guide motor behavior. Over the years, numerous studies employing diverse techniques such as electrophysiology, imaging, and optogenetics have revealed a complex network of neural circuits involved in the regulation of emotional or motor processes. Emotions can exert a substantial influence on motor performance, encompassing both everyday activities and pathological conditions. The aim of this review is to explore how emotional states can shape movements by connecting the neural circuits for emotional processing to motor neural circuits. We first provide a comprehensive overview of the impact of different emotional states on motor control in humans and rodents. In line with behavioral studies, we set out to identify emotion-related structures capable of modulating motor output, behaviorally and anatomically. Neuronal circuits involved in emotional processing are extensively connected to the motor system. These circuits can drive emotional behavior, essential for survival, but can also continuously shape ongoing movement. In summary, the investigation of the intricate relationship between emotion and movement offers valuable insights into human behavior, including opportunities to enhance performance, and holds promise for improving mental and physical health. This review integrates findings from multiple scientific approaches, including anatomical tracing, circuit-based dissection, and behavioral studies, conducted in both animal and human subjects. By incorporating these different methodologies, we aim to present a comprehensive overview of the current understanding of the emotional modulation of movement in both physiological and pathological conditions.

Dissection of the bed nucleus of the stria terminalis neuronal subtypes in feeding regulation

The bed nucleus of the stria terminalis (BNST) plays an important role in feeding regulation through projections to other brain areas. However, whether functional distinctions exist within different BNST cells is not clear. Here, we found optogenetic activation of LH-projecting BNST neurons induced aversion and significantly reduced consumption of normal chow but not high-fat diets (HFD). In contrast, photoactivation of vlPAG-projecting BNST neurons induced place preference and promoted HFD intake, without affecting normal chow consumption. Moreover, optogenetic silencing of LH-projecting BNST neurons reduced the consumption of normal chow in fasted mice, while photoinhibition of vlPAG-projecting BNST neurons decreased the consumption of HFD in both fed and fasted mice. We then labeled the LH- and vlPAG-projecting BNST neurons using retroAAV-GFP and retroAAV-mCherry, respectively, and found these two populations of neurons have different anatomical distribution and electrophysiological properties. Taken together, we identified vlPAG-projecting and LH-projecting BNST neurons are two distinct populations of cells with significant differences in functional and anatomic characteristics.

Bed nucleus of the stria terminalis GABA neurons are necessary for changes in foraging behaviour following an innate threat

Foraging is a universal behaviour that has co-evolved with predation pressure. We investigated the role of the bed nucleus of the stria terminalis (BNST) GABA neurons in robotic and live predator threat processing and their consequences in post-threat encounter foraging. Both robotic and live predator interactions increased BNST GABA neuron activity. Mice were trained to procure food in a laboratory-based foraging apparatus in which food pellets were placed at incrementally greater distances from a nest zone. After mice learned to forage, they were exposed to a robotic or live predator threat, while BNST GABA neurons were chemogenetically inhibited. Post-robotic threat encounter, mice spent more time in the nest zone, but other foraging parameters were unchanged compared with pre-encounter behaviour. Inhibition of BNST GABA neurons had no effect on foraging behaviour post-robotic threat encounter. Following live predator exposure, control mice spent significantly more time in the nest zone, increased their latency to successfully forage, and significantly altered their overall foraging performance. Inhibition of BNST GABA neurons during live predator exposure prevented changes in foraging behaviour from developing after a live predator threat. BNST GABA neuron inhibition did not alter foraging behaviour during robotic or live predator threats. We conclude that these results demonstrate that while both robotic and live predator encounters effectively intrude on foraging behaviour, the perceived risk and behavioural consequences of the threat are distinguishable. Additionally, BNST GABA neurons may play a role in the integration of prior innate predator threat experience that results in hypervigilance during post-encounter foraging behaviour.

Recruitment of Hippocampal and Thalamic Pathways to the Central Amygdala in the Control of Feeding Behavior Under Novelty

It is adaptive to restrict eating under uncertainty, such as during habituation to novel foods and unfamiliar environments. However, sustained restrictive eating is a core symptom of eating disorders and has serious long-term health consequences. Current therapeutic efforts are limited, because the neural substrates of restrictive eating are poorly understood. Using a model of feeding avoidance under novelty, our recent study identified forebrain activation patterns and found evidence that the central nucleus of the amygdala (CEA) is a core integrating node. The current study analyzed the activity of CEA inputs in male and female rats to determine if specific pathways are recruited during feeding under novelty. Recruitment of direct inputs from the paraventricular nucleus of the thalamus (PVT), the infralimbic cortex (ILA), the agranular insular cortex (AI), the hippocampal ventral field CA1, and the bed nucleus of the stria terminals (BST) was assessed with combined retrograde tract tracing and Fos induction analysis. The study found that during consumption of a novel food in a novel environment, larger number of neurons within the PVTp and the CA1 that send monosynaptic inputs to the CEA were recruited compared to controls that consumed familiar food in a familiar environment. The ILA, AI, and BST inputs to the CEA were similarly recruited across conditions. There were no sex differences in activation of any of the pathways analyzed. These results suggest that the PVTp-CEA and CA1-CEA pathways underlie feeding inhibition during novelty and could be potential sites of malfunction in excessive food avoidance.

Distinct Circuits From the Central Lateral Amygdala to the Ventral Part of the Bed Nucleus of Stria Terminalis Regulate Different Fear Memory

BACKGROUND

The ability to differentiate stimuli that predict fear is critical for survival; however, the underlying molecular and circuit mechanisms remain poorly understood.

METHODS

We combined transgenic mice, in vivo transsynaptic circuit-dissecting anatomical approaches, optogenetics, pharmacological methods, and electrophysiological recording to investigate the involvement of specific extended amygdala circuits in different fear memory.

RESULTS

We identified the projections from central lateral amygdala (CeL) protein kinase C δ (PKCδ)-positive neurons and somatostatin (SST)-positive neurons to GABAergic (gamma-aminobutyric acidergic) and glutamatergic neurons in the ventral part of the bed nucleus of stria terminalis (vBNST). Prolonged optogenetic activation or inhibition of the PKCδCeL-vBNST pathway specifically reduced context fear memory, whereas the SSTCeL-vBNST pathway mainly reduced tone fear memory. Intriguingly, optogenetic manipulation of vBNST neurons that received the projection from PKCδCeL neurons exerted bidirectional regulation of context fear, whereas manipulation of vBNST neurons that received the projection from SSTCeL neurons could bidirectionally regulate both context and tone fear memory. We subsequently demonstrated the presence of δ and κ opioid receptor protein expression within the CeL-vBNST circuits, potentially accounting for the discrepancy between prolonged activation of GABAergic circuits and inhibition of downstream vBNST neurons. Finally, administration of an opioid receptor antagonist cocktail on the PKCδCeL-vBNST or SSTCeL-vBNST pathway successfully restored context or tone fear memory reduction induced by prolonged activation of the circuits.

CONCLUSIONS

Together, these findings establish a functional role for distinct CeL-vBNST circuits in the differential regulation and appropriate maintenance of fear.

Propranolol blocks the unconditioned and conditioned hyperactive effects of methamphetamine in CD-1 mice

The present experiment examined the contribution of the β-adrenergic receptor system in mediating the unconditioned (i.e. pharmacological) and conditioned (i.e. learned) hyperactive effects of methamphetamine. To this end, mice underwent an 8-day conditioning procedure involving two different, alternating session types (chamber and home-cage days). On chamber days (1, 3, 5, and 7), mice were injected (intraperitoneally) with vehicle (dH 2 O) or propranolol (16 or 32 mg/kg) and were injected (subcutaneously) 30 min (min) later by either vehicle (saline; unpaired) or methamphetamine (1.0 mg/kg; paired). On home-cage days (2, 4, 6, and 8), mice were injected (subcutaneously) with either vehicle (saline; paired) or methamphetamine (1.0 mg/kg; unpaired) in their home cages. The test day for conditioned hyperactivity occurred 48 h after the last chamber day. Propranolol dose-dependently blocked the unconditioned and conditioned hyperactive effects of methamphetamine, implicating a role for the β-adrenergic system in mediating these effects of methamphetamine.

The neurophysiological basis of stress and anxiety - comparing neuronal diversity in the bed nucleus of the stria terminalis (BNST) across species

The bed nucleus of the stria terminalis (BNST), as part of the extended amygdala, has become a region of increasing interest regarding its role in numerous human stress-related psychiatric diseases, including post-traumatic stress disorder and generalized anxiety disorder amongst others. The BNST is a sexually dimorphic and highly complex structure as already evident by its anatomy consisting of 11 to 18 distinct sub-nuclei in rodents. Located in the ventral forebrain, the BNST is anatomically and functionally connected to many other limbic structures, including the amygdala, hypothalamic nuclei, basal ganglia, and hippocampus. Given this extensive connectivity, the BNST is thought to play a central and critical role in the integration of information on hedonic-valence, mood, arousal states, processing emotional information, and in general shape motivated and stress/anxiety-related behavior. Regarding its role in regulating stress and anxiety behavior the anterolateral group of the BNST (BNSTALG) has been extensively studied and contains a wide variety of neurons that differ in their electrophysiological properties, morphology, spatial organization, neuropeptidergic content and input and output synaptic organization which shape their activity and function. In addition to this great diversity, further species-specific differences are evident on multiple levels. For example, classic studies performed in adult rat brain identified three distinct neuron types (Type I-III) based on their electrophysiological properties and ion channel expression. Whilst similar neurons have been identified in other animal species, such as mice and non-human primates such as macaques, cross-species comparisons have revealed intriguing differences such as their comparative prevalence in the BNSTALG as well as their electrophysiological and morphological properties, amongst other differences. Given this tremendous complexity on multiple levels, the comprehensive elucidation of the BNSTALG circuitry and its role in regulating stress/anxiety-related behavior is a major challenge. In the present Review we bring together and highlight the key differences in BNSTALG structure, functional connectivity, the electrophysiological and morphological properties, and neuropeptidergic profiles of BNSTALG neurons between species with the aim to facilitate future studies of this important nucleus in relation to human disease.

Whole-brain connectivity to the bed nucleus of the stria terminalis calretinin-expressing interneurons in male mice

The bed nucleus of the stria terminalis (BNST) is a neuropeptide-enriched brain region that modulates a wide variety of emotional behaviours and states, including stress, anxiety, reward and social interaction. The BNST consists of diverse subregions and neuronal ensembles; however, because of the high molecular heterogeneity within BNST neurons, the mechanisms through which the BNST regulates distinct emotional behaviours remain largely unclear. Prior studies have identified BNST calretinin (CR)-expressing neurons, which lack neuropeptides. Here, employing virus-based cell-type-specific retrograde and anterograde tracing systems, we mapped the whole-brain monosynaptic inputs and axonal projections of BNST CR-expressing neurons in male mice. We found that BNST CR-expressing neurons received inputs mainly from the amygdalopiriform transition area, central amygdala and hippocampus and moderately from the medial preoptic area, basolateral amygdala, paraventricular thalamus and lateral hypothalamus. Within the BNST, plenty of input neurons were primarily located in the oval and interfascicular subregions. Furthermore, numerous BNST CR-expressing neuronal boutons were observed within the BNST but not in other brain regions, thus suggesting that these neurons are a type of interneuron. These results will help further elucidate the neuronal circuits underlying the elaborate and distinct functions of the BNST.

Dorsal BNST DRD2+ neurons mediate sex-specific anxiety-like behavior induced by chronic social isolation

The dorsal bed nucleus of stria terminalis (dBNST) is a pivotal hub for stress response modulation. Dysfunction of dopamine (DA) network is associated with chronic stress, but the roles of DA network of dBNST in chronic stress-induced emotional disorders remain unclear. We examine the role of dBNST Drd1⁺ and Drd2⁺ neurons in post-weaning social isolation (PWSI)-induced behavior deficits. We find that male, but not female, PWSI rats exhibit negative emotional phenotypes and the increase of excitability and E-I balance of dBNST Drd2⁺ neurons. More importantly, hypofunction of dBNST Drd2 receptor underlies PWSI-stress-induced male-specific neuronal plasticity change of dBNST Drd2⁺ neurons. Furthermore, chemogenetic activation of dBNST Drd2⁺ neurons is sufficient to induce anxiogenic effects, while Kir4.1-mediated chronic inhibition of dBNST Drd2⁺ neurons ameliorate PWSI-induced anxiety-like behaviors. Our findings reveal an important neural mechanism underlying PWSI-induced sex-specific behavioral abnormalities and potentially provide a target for the treatment of social stress-related emotional disorder.

Parallel Olfactory Systems Synergistically Activate the Posteroventral Part of the Medial Amygdala Upon Alarm Pheromone Detection in Rats

In rats, a mixture of hexanal and 4-methylpentanal is a main component of the alarm pheromone. When detected by the main olfactory system (MOS) and the vomeronasal system, respectively, they activate the anterior part of the bed nucleus of the stria terminalis (BNSTa). Therefore, the information from the two olfactory systems is expected to be integrated before being transmitted to the BNSTa. To specify the integration site, we examined Fos expression in 16 brain regions in response to water (n = 10), hexanal (n = 9), 4-methylpentanal (n = 9), the mixture (n = 9), or the alarm pheromone (n = 9) in male rats. The posteroventral part of the medial amygdala showed increased Fos expression to hexanal and 4-methylpentanal. The expression was further increased by the mixture. Therefore, this region is suggested as the integration site. In addition, the BNSTa, paraventricular nucleus of the hypothalamus, and anteroventral, anterodorsal, and posterodorsal parts of the medial amygdala were suggested to be located downstream of the integrated site because only the mixture increased Fos expression. We suggest that the posterolateral part of the cortical amygdala is upstream of the integration site in the MOS because all stimuli increased Fos expression. The posterior part of the bed nucleus of the stria terminalis and posteromedial part of the cortical amygdala were suggested as being located upstream in the vomeronasal system because 4-methylpentanal and the mixture increased Fos expression. These results provide information about the neural pathway underlying the alarm pheromone effects.

BNST PKCδ neurons are activated by specific aversive conditions to promote anxiety-like behavior

The bed nucleus of the stria terminalis (BNST) is a critical mediator of stress responses and anxiety-like behaviors. Neurons expressing protein kinase C delta (BNSTPKCδ) are an abundant but understudied subpopulation implicated in inhibiting feeding, but which have conflicting reports about their role in anxiety-like behaviors. We have previously shown that expression of PKCδ is dynamically regulated by stress and that BNSTPKCδ cells are recruited during bouts of active stress coping. Here, we first show that in vivo activation of this population is mildly aversive. This aversion was insensitive to prior restraint stress exposure. Further investigation revealed that unlike other BNST subpopulations, BNSTPKCδ cells do not exhibit increased cfos expression following restraint stress. Ex vivo current clamp recordings also indicate they are resistant to firing. To elucidate their afferent control, we next used rabies tracing with whole-brain imaging and channelrhodopsin-assisted circuit mapping, finding that BNSTPKCδ cells receive abundant input from affective, arousal, and sensory regions including the basolateral amygdala (BLA) paraventricular thalamus (PVT) and central amygdala PKCδ-expressing cells (CeAPKCδ). Given these findings, we used in vivo optogenetics and fiber photometry to further examine BNSTPKCδ cells in the context of stress and anxiety-like behavior. We found that BNSTPKCδ cell activity is associated with increased anxiety-like behavior in the elevated plus maze, increases following footshock, and unlike other BNST subpopulations, does not desensitize to repeated stress exposure. Taken together, we propose a model in which BNSTPKCδ cells may serve as threat detectors, integrating exteroceptive and interoceptive information to inform stress coping behaviors.

Pharmacological Inactivation of the Bed Nucleus of the Stria Terminalis Increases Affiliative Social Behavior in Rhesus Macaques

The bed nucleus of the stria terminalis (BNST) has been implicated in a variety of social behaviors, including aggression, maternal care, mating behavior, and social interaction. Limited evidence from rodent studies suggests that activation of the BNST results in a decrease in social interaction between unfamiliar animals. The role of the BNST in social interaction in primates remains wholly unexamined. Nonhuman primates provide a valuable model for studying social behavior because of both their rich social repertoire and neural substrates of behavior with high translational relevance to humans. To test the hypothesis that the primate BNST is a critical modulator of social behavior, we performed intracerebral microinfusions of the GABAA agonist muscimol to transiently inactivate the BNST in male macaque monkeys. We measured changes in social interaction with a familiar same-sex conspecific. Inactivation of the BNST resulted in significant increase in total social contact. This effect was associated with an increase in passive contact and a significant decrease in locomotion. Other nonsocial behaviors (sitting passively alone, self-directed behaviors, and manipulation) were not impacted by BNST inactivation. As part of the "extended amygdala," the BNST is highly interconnected with the basolateral (BLA) and central (CeA) nuclei of the amygdala, both of which also play critical roles in regulating social interaction. The precise pattern of behavioral changes we observed following inactivation of the BNST partially overlaps with our prior reports in the BLA and CeA. Together, these data demonstrate that the BNST is part of a network regulating social behavior in primates.SIGNIFICANCE STATEMENT The bed nucleus of the stria terminalis (BNST) has a well-established role in anxiety behaviors, but its role in social behavior is poorly understood. No prior studies have evaluated the impact of BNST manipulations on social behavior in primates. We found that transient pharmacological inactivation of the BNST increased social behavior in pairs of macaque monkeys. These data suggest the BNST contributes to the brain networks regulating sociability.

Angiotensinergic neurotransmission in the bed nucleus of the stria terminalis is involved in cardiovascular responses to acute restraint stress in rats

The brain angiotensin II acting via AT₁ receptors is a prominent mechanism involved in physiological and behavioral responses during aversive situations. The AT₂ receptor has also been implicated in stress responses, but its role was less explored. Despite these pieces of evidence, the brain sites related to control of the changes during aversive threats by the brain renin-angiotensin system (RAS) are poorly understood. The bed nucleus of the stria terminalis (BNST) is a limbic structure related to the cardiovascular responses by stress, and components of the RAS system were identified in this forebrain region. Therefore, we investigated the role of angiotensinergic neurotransmission present within the BNST acting via local AT₁ and AT₂ receptors in cardiovascular responses evoked by an acute session of restraint stress in rats. For this, rats were subjected to bilateral microinjection of either the angiotensin-converting enzyme inhibitor captopril, the selective AT₁ receptor antagonist losartan, or the selective AT₂ receptor antagonist PD123319 before they underwent the restraint stress session. We observed that BNST treatment with captopril reduced the decrease in tail skin temperature evoked by restraint stress, without affecting the pressor and tachycardic responses. Local AT₂ receptor antagonism within the BNST reduced both the tachycardia and the drop in tail skin temperature during restraint. Bilateral microinjection of losartan into the BNST did not affect the restraint-evoked cardiovascular changes. Taken together, these data indicate an involvement of BNST angiotensinergic neurotransmission acting via local AT₂ receptors in cardiovascular responses during stressful situations.

Bed nucleus of the stria terminalis CB1 receptors and the FAAH enzyme modulate anxiety behavior depending on previous stress exposure

The endocannabinoid (eCB) anandamide (AEA) is synthesized on-demand in the post-synaptic terminal and can act on presynaptic cannabinoid type 1 (CB1) receptors, decreasing the release of neurotransmitters, including glutamate. AEA action is ended through enzymatic hydrolysis via FAAH (fatty acid amid hydrolase) in the post-synaptic neuron. eCB system molecules are widely expressed in brain areas involved in the modulation of fear and anxiety responses, including the Bed Nucleus of the Stria Terminalis (BNST), which is involved in the integration of autonomic, neuroendocrine, and behavioral regulation. The presence of the CB1 and FAAH was described in the BNST; however, their role in the modulation of defensive reactions is not fully comprehended. In the present work we aimed at investigating the role of AEA and CB1 receptors in the BNST in modulating anxiety-related behaviors. Adult male Wistar rats received local BNST injections of the CB1 receptor antagonist AM251 (0.1-0.6 nmol) and/or the FAAH inhibitor (URB597; 0.001-0.1 nmol) and were evaluated in the elevated plus maze (EPM) test, with or without previous acute restraint stress (2 h) exposure, or in the contextual fear conditioning. We observed that although AM251 and URB597 had no effects on the EPM, they increased and decreased, respectively, the conditioned fear response. Supporting a possible influence of stress in these differences, URB597 was able to prevent the restraint stress-induced anxiogenic effect in the EPM. The present data, therefore, suggest that eCB signaling in the BNST is recruited during more aversive situations to counteract the stress effect.

Bed nuclei of the stria terminalis: A key hub in the modulation of anxiety

The bed nuclei of the stria terminalis (BST) is recognised as a pivotal integrative centre for monitoring emotional valence. It is implicated in the regulation of diverse affective states and motivated behaviours, and decades of research have firmly established its critical role in anxiety-related behavioural processes. Researchers have recently intricately dissected the BST's dynamic activities, its connection patterns and its functions with respect to specific cell types using multiple techniques such as optogenetics, in vivo calcium imaging and transgenic tools to unmask the complex circuitry mechanisms that underlie anxiety. In this review, we principally focus on studies of anxiety-involved neuromodulators within the BST and provide a comprehensive architecture of the anxiety network-highlighting the BST as a key hub in orchestrating anxiety-like behaviour. We posit that these promising efforts will contribute to the identification of an accurate roadmap for future treatment of anxiety disorders.

Whole-brain input mapping of the lateral versus medial anterodorsal bed nucleus of the stria terminalis in the mouse

The anterior portion of the bed nucleus of the stria terminalis (BNST) modulates fear and stress responses. The anterodorsal BNST (adBNST) can be anatomically subdivided further into the lateral and medial divisions. Although output projections of BNST subregions have been studied, the local and global input connections to these subregions remain poorly understood. To further understand BNST-centered circuit operations, we have applied new viral-genetic tracing and functional circuit mapping to determine detailed synaptic circuit inputs to lateral and medial subregions of adBNST in the mouse. Monosynaptic canine adenovirus type 2 (CAV2) and rabies virus-based retrograde tracers were injected in the adBNST subregions. The amygdalar complex, hypothalamus and hippocampal formation account for the majority of overall inputs to adBNST. However, lateral versus medial adBNST subregions have distinct patterns of long-range cortical and limbic brain inputs. The lateral adBNST has more input connections from prefrontal (prelimbic, infralimbic, cingulate) and insular cortices, anterior thalamus and ectorhinal/perirhinal cortices. In contrast, the medial adBNST received biased inputs from the medial amygdala, lateral septum, hypothalamus nuclei and ventral subiculum. We confirmed long-range functional inputs from the amydalohippocampal area and basolateral amygdala to the adBNST using ChR2-assisted circuit mapping. Selected novel BNST inputs are also validated with the AAV axonal tracing data from the Allen Institute Mouse Brain Connectivity Atlas. Together, these results provide a comprehensive map of the differential afferent inputs to lateral and medial adBNST subregions, and offer new insight into the functional operations of BNST circuitry for stress and anxiety-related behaviors.

Chemogenetic inhibition of the bed nucleus of the stria terminalis suppresses the intake of a preferable and learned aversive sweet taste solution in male mice

Conditioned taste aversion (CTA) is established by pairing a taste solution as a conditioned stimulus (CS) with visceral malaise as an unconditioned stimulus (US). CTA decreases the taste palatability of a CS. The bed nucleus of the stria terminalis (BNST) receives taste inputs from the brainstem. However, the involvement of the BNST in CTA remains unclear. Thus, this study examined the effects of chemogenetic inhibition of the BNST neurons on CS intake after CTA acquisition. An adeno-associated virus was microinjected into the BNST of male C57/BL6 mice to induce the inhibitory designer receptor hM4Di. The mice received a pairing of 0.2% saccharin solution (CS) with 0.3 M lithium chloride (2% BW, intraperitoneal). After conditioning, the administration of clozapine-N-oxide (CNO, 1 mg/kg) significantly enhanced the suppression of CS intake on the retrieval of CTA compared with its intake following saline administration (p < 0.01). We further assessed the effect of BNST neuron inhibition on the intake of water and taste solutions (saccharin, sucralose, sodium chloride, monosodium glutamate, quinine hydrochloride, and citric acid) using naïve (not learned CTA) mice. CNO administration significantly decreased the intake of saccharin and sucralose (p < 0.05). Our results indicate that BNST neurons mediate sweet taste and regulate sweet intake, regardless of whether sweets should be ingested or rejected. BNST neurons may be inhibited in the retrieval of CTA, thereby suppressing CS intake.

The role of the bed nucleus of the stria terminalis in the motivational control of instrumental action

We review recent studies assessing the role of the bed nucleus of the stria terminalis (BNST) in the motivational control of instrumental conditioning. This evidence suggests that the BNST and central nucleus of the amygdala (CeA) form a circuit that modulates the ventral tegmental area (VTA) input to the nucleus accumbens core (NAc core) to control the influence of Pavlovian cues on instrumental performance. In support of these claims, we found that activity in the oval region of BNST was increased by instrumental conditioning, as indexed by phosphorylated ERK activity (Experiment 1), but that this increase was not due to exposure to the instrumental contingency or to the instrumental outcome per se (Experiment 2). Instead, BNST activity was most significantly incremented in a test conducted when the instrumental outcome was anticipated but not delivered, suggesting a role for BNST in the motivational effects of anticipated outcomes on instrumental performance. To test this claim, we examined the effect of NMDA-induced cell body lesions of the BNST on general Pavlovian-to-instrumental transfer (Experiment 3). These lesions had no effect on instrumental performance or on conditioned responding during Pavlovian conditioning to either an excitory conditioned stimulus (CS) or a neutral CS (CS0) but significantly attenuated the excitatory effect of the Pavlovian CS on instrumental performance. These data are consistent with the claim that the BNST mediates the general excitatory influence of Pavlovian cues on instrumental performance and suggest BNST activity may be central to CeA-BNST modulation of a VTA-NAc core circuit in incentive motivation.

Functional brain-wide network mapping during acute stress exposure in rats: Interaction between the lateral habenula and cortical, amygdalar, hypothalamic and monoaminergic regions

Upon stress exposure, a broad network of structures comes into play in order to provide adequate responses and restore homeostasis. It has been known for decades that the main structures engaged during the stress response are the medial prefrontal cortex, the amygdala, the hippocampus, the hypothalamus, the monoaminergic systems (noradrenaline, dopamine and serotonin) and the periaqueductal gray. The lateral habenula (LHb) is an epithalamic structure directly connected to prefrontal cortical areas and to the amygdala, whereas it functionally interacts with the hippocampus. Also, it is a main modulator of monoaminergic systems. The LHb is activated upon exposure to basically all types of stressors, suggesting it is also involved in the stress response. However, it remains unknown if and how the LHb functionally interacts with the broad stress response network. In the current study we performed in rats a restraint stress procedure followed by immunohistochemical staining of the c-Fos protein throughout the brain. Using graph theory-based functional connectivity analyses, we confirm the principal hubs of the stress network (e.g., prefrontal cortex, amygdala and periventricular hypothalamus) and show that the LHb is engaged during stress exposure in close interaction with the medial prefrontal cortex, the lateral septum and the medial habenula. In addition, we performed DREADD-induced LHb inactivation during the same restraint paradigm in order to explore its consequences on the stress response network. This last experiment gave contrasting results as the DREADD ligand alone, clozapine-N-oxide, was able to modify the network.

What the hippocampus tells the HPA axis: Hippocampal output attenuates acute stress responses via disynaptic inhibition of CRF+ PVN neurons

The hippocampus exerts inhibitory feedback on the release of glucocorticoids. Because the major hippocampal efferent projections are excitatory, it has been hypothesized that this inhibition is mediated by populations of inhibitory neurons in the hypothalamus or elsewhere. These regions would be excited by hippocampal efferents and project to corticotropin-releasing factor (CRF) cells in the paraventricular nucleus of the hypothalamus (PVN). A direct demonstration of the synaptic responses elicited by hippocampal outputs in PVN cells or upstream GABAergic interneurons has not been provided previously. Here, we used viral vectors to express channelrhodopsin (ChR) and enhanced yellow fluorescent protein (EYFP) in pyramidal cells in the ventral hippocampus (vHip) in mice expressing tdTomato in GABA- or CRF-expressing neurons. We observed dense innervation of the bed nucleus of the stria terminalis (BNST) by labeled vHip axons and sparse labeling within the PVN. Using whole-cell voltage-clamp recording in parasagittal brain slices containing the BNST and PVN, photostimulation of vHip terminals elicited rapid excitatory postsynaptic currents (EPSCs) and longer-latency inhibitory postsynaptic currents (IPSCs) in both CRF+ and GAD + cells. The ratio of synaptic excitation and inhibition was maintained in CRF + cells during 20 Hz stimulus trains. Photostimulation of hippocampal afferents to the BNST and PVN in vivo inhibited the rise in blood glucocorticoid levels produced by acute restraint stress. We thus provide functional evidence suggesting that hippocampal output to the BNST contributes to a net inhibition of the hypothalamic-pituitary axis, providing further mechanistic insights into this process using methods with enhanced spatial and temporal resolution.

Chronic stress-induced synaptic changes to corticotropin-releasing factor-signaling in the bed nucleus of the stria terminalis

The sexually dimorphic bed nucleus of the stria terminalis (BNST) is comprised of several distinct regions, some of which act as a hub for stress-induced changes in neural circuitry and behavior. In rodents, the anterodorsal BNST is especially affected by chronic exposure to stress, which results in alterations to the corticotropin-releasing factor (CRF)-signaling pathway, including CRF receptors and upstream regulators. Stress increases cellular excitability in BNST CRF+ neurons by potentiating miniature excitatory postsynaptic current (mEPSC) amplitude, altering the resting membrane potential, and diminishing M-currents (a voltage-gated K+ current that stabilizes membrane potential). Rodent anterodorsal and anterolateral BNST neurons are also critical regulators of behavior, including avoidance of aversive contexts and fear learning (especially that of sustained threats). These rodent behaviors are historically associated with anxiety. Furthermore, BNST is implicated in stress-related mood disorders, including anxiety and Post-Traumatic Stress Disorders in humans, and may be linked to sex differences found in mood disorders.

Disruption of Synaptic Transmission in the Bed Nucleus of the Stria Terminalis Reduces Seizure-Induced Death in DBA/1 Mice and Alters Brainstem E/I Balance

Sudden unexpected death in epilepsy (SUDEP) is the leading cause of death in refractory epilepsy patients. Accumulating evidence from recent human studies and animal models suggests that seizure-related respiratory arrest may be important for initiating cardiorespiratory arrest and death. Prior evidence suggests that apnea onset can coincide with seizure spread to the amygdala and that stimulation of the amygdala can reliably induce apneas in epilepsy patients, potentially implicating amygdalar regions in seizure-related respiratory arrest and subsequent postictal hypoventilation and cardiorespiratory death. This study aimed to determine if an extended amygdalar structure, the dorsal bed nucleus of the stria terminalis (dBNST), is involved in seizure-induced respiratory arrest (S-IRA) and death using DBA/1 mice, a mouse strain which has audiogenic seizures (AGS) and a high incidence of postictal respiratory arrest and death. The presence of S-IRA significantly increased c-Fos expression in the dBNST of DBA/1 mice. Furthermore, disruption of synaptic output from the dBNST via viral-induced tetanus neurotoxin (TeNT) significantly improved survival following S-IRA in DBA/1 mice without affecting baseline breathing or hypercapnic (HCVR) and hypoxic ventilatory response (HVR). This disruption in the dBNST resulted in changes to the balance of excitatory/inhibitory (E/I) synaptic events in the downstream brainstem regions of the lateral parabrachial nucleus (PBN) and the periaqueductal gray (PAG). These findings suggest that the dBNST is a potential subcortical forebrain site necessary for the mediation of S-IRA, potentially through its outputs to brainstem respiratory regions.

Coordination of social behaviors by the bed nucleus of the stria terminalis

The bed nucleus of the stria terminalis (BNST) is a sexually dimorphic, neuropeptide-rich node of the extended amygdala that has been implicated in responses to stress, drugs of abuse, and natural rewards. Its function is dysregulated in neuropsychiatric disorders that are characterized by stress- or drug-induced alterations in mood, arousal, motivation, and social behavior. However, compared to the BNST's role in mood, arousal, and motivation, its role in social behavior has remained relatively understudied. Moreover, the precise cell types and circuits underlying the BNST's role in social behavior have only recently begun to be explored using modern neuroscience techniques. Here, we systematically review the existing literature investigating the neurobiological substrates within the BNST that contribute to the coordination of various sex-dependent and sex-independent social behavioral repertoires, focusing largely on pharmacological and circuit-based behavioral studies in rodents. We suggest that the BNST coordinates social behavior by promoting appropriate assessment of social contexts to select relevant behavioral outputs and that disruption of socially relevant BNST systems by stress and drugs of abuse may be an important factor in the development of social dysfunction in neuropsychiatric disorders.

Chronic pain-induced neuronal plasticity in the bed nucleus of the stria terminalis causes maladaptive anxiety

The comorbidity of chronic pain and mental dysfunctions such as depression and anxiety disorders has long been recognized, but the underlying mechanisms remain poorly understood. Here, using a mouse model of neuropathic pain, we demonstrated neuronal plasticity in the bed nucleus of the stria terminalis (BNST), which plays a critical role in chronic pain-induced maladaptive anxiety. Electrophysiology demonstrated that chronic pain increased inhibitory inputs to lateral hypothalamus (LH)-projecting BNST neurons. Chemogenetic manipulation revealed that sustained suppression of LH-projecting BNST neurons played a crucial role in chronic pain-induced anxiety. Furthermore, using a molecular genetic approach, we demonstrated that chronic pain elevated the excitability of a specific subpopulation of BNST neurons, which express cocaine- and amphetamine-regulated transcript (CART). The elevated excitability of CART-positive neurons caused the increased inhibitory inputs to LH-projecting BNST neurons, thereby inducing anxiety-like behavior. These findings shed light on how chronic pain induces psychiatric disorders, characterized by maladaptive anxiety.

Autonomic Neural Circuit and Intervention for Comorbidity Anxiety and Cardiovascular Disease

Anxiety disorder is a prevalent psychiatric disease and imposes a significant influence on cardiovascular disease (CVD). Numerous evidence support that anxiety contributes to the onset and progression of various CVDs through different physiological and behavioral mechanisms. However, the exact role of nuclei and the association between the neural circuit and anxiety disorder in CVD remains unknown. Several anxiety-related nuclei, including that of the amygdala, hippocampus, bed nucleus of stria terminalis, and medial prefrontal cortex, along with the relevant neural circuit are crucial in CVD. A strong connection between these nuclei and the autonomic nervous system has been proven. Therefore, anxiety may influence CVD through these autonomic neural circuits consisting of anxiety-related nuclei and the autonomic nervous system. Neuromodulation, which can offer targeted intervention on these nuclei, may promote the development of treatment for comorbidities of CVD and anxiety disorders. The present review focuses on the association between anxiety-relevant nuclei and CVD, as well as discusses several non-invasive neuromodulations which may treat anxiety and CVD.

Role of deep brain stimulation in management of psychiatric disorders

Nowadays, most of patients affected by psychiatric disorders are successfully treated with conservative therapies. Still, a variable percentage of them demonstrate resistance to conventional treatments, and alternative methods can then be considered. During the last 20 years, there is a progressive interest in use of deep brain stimulation (DBS) in mental illnesses. It has become clear nowadays, that this modality may be effectively applied under specific indications in some patients with major depressive disorder, obsessive-compulsive disorder, anorexia nervosa and other eating disorders, Tourette syndrome, schizophrenia, substance use disorder, and even pathologically aggressive behavior. Despite the fact that the efficacy of neuromodulation with DBS, as well as of various lesional interventions, in cases of mental illnesses is still not fully established, there are several premises for wider applications of such "unclassical" psychiatric treatments in the future. Novel technologies of DBS, developments in non-invasive lesioning using stereotactic radiosurgery and transcranial magnetic resonance-guided focused ultrasound, and advances of neurophysiological and neuroimaging modalities may bolster further clinical applications of psychiatric neurosurgery, improve its results, and allow for individually selected treatment strategies tailored to specific needs of the patient.

The physiological control of eating: signals, neurons, and networks

During the past 30 yr, investigating the physiology of eating behaviors has generated a truly vast literature. This is fueled in part by a dramatic increase in obesity and its comorbidities that has coincided with an ever increasing sophistication of genetically based manipulations. These techniques have produced results with a remarkable degree of cell specificity, particularly at the cell signaling level, and have played a lead role in advancing the field. However, putting these findings into a brain-wide context that connects physiological signals and neurons to behavior and somatic physiology requires a thorough consideration of neuronal connections: a field that has also seen an extraordinary technological revolution. Our goal is to present a comprehensive and balanced assessment of how physiological signals associated with energy homeostasis interact at many brain levels to control eating behaviors. A major theme is that these signals engage sets of interacting neural networks throughout the brain that are defined by specific neural connections. We begin by discussing some fundamental concepts, including ones that still engender vigorous debate, that provide the necessary frameworks for understanding how the brain controls meal initiation and termination. These include key word definitions, ATP availability as the pivotal regulated variable in energy homeostasis, neuropeptide signaling, homeostatic and hedonic eating, and meal structure. Within this context, we discuss network models of how key regions in the endbrain (or telencephalon), hypothalamus, hindbrain, medulla, vagus nerve, and spinal cord work together with the gastrointestinal tract to enable the complex motor events that permit animals to eat in diverse situations.

Childhood Threat Is Associated With Lower Resting-State Connectivity Within a Central Visceral Network

Childhood adversity is associated with altered or dysregulated stress reactivity; these altered patterns of physiological functioning persist into adulthood. Evidence from both preclinical animal models and human neuroimaging studies indicates that early life experience differentially influences stressor-evoked activity within central visceral neural circuits proximally involved in the control of stress responses, including the subgenual anterior cingulate cortex (sgACC), paraventricular nucleus of the hypothalamus (PVN), bed nucleus of the stria terminalis (BNST) and amygdala. However, the relationship between childhood adversity and the resting-state connectivity of this central visceral network remains unclear. To this end, we examined relationships between childhood threat and childhood socioeconomic deprivation, the resting-state connectivity between our regions of interest (ROIs), and affective symptom severity and diagnoses. We recruited a transdiagnostic sample of young adult males and females (n = 100; mean age = 27.28, SD = 3.99; 59 females) with a full distribution of maltreatment history and symptom severity across multiple affective disorders. Resting-state data were acquired using a 7.2-min functional magnetic resonance imaging (fMRI) sequence; noted ROIs were applied as masks to determine ROI-to-ROI connectivity. Threat was determined by measures of childhood traumatic events and abuse. Socioeconomic deprivation (SED) was determined by a measure of childhood socioeconomic status (parental education level). Covarying for age, race and sex, greater childhood threat was significantly associated with lower BNST-PVN, amygdala-sgACC and PVN-sgACC connectivity. No significant relationships were found between SED and resting-state connectivity. BNST-PVN connectivity was associated with the number of lifetime affective diagnoses. Exposure to threat during early development may entrain altered patterns of resting-state connectivity between these stress-related ROIs in ways that contribute to dysregulated neural and physiological responses to stress and subsequent affective psychopathology.

Amylin-Calcitonin receptor signaling in the medial preoptic area mediates affiliative social behaviors in female mice

Social animals actively engage in contact with conspecifics and experience stress upon isolation. However, the neural mechanisms coordinating the sensing and seeking of social contacts are unclear. Here we report that amylin-calcitonin receptor (Calcr) signaling in the medial preoptic area (MPOA) mediates affiliative social contacts among adult female mice. Isolation of females from free social interactions first induces active contact-seeking, then depressive-like behavior, concurrent with a loss of Amylin mRNA expression in the MPOA. Reunion with peers induces physical contacts, activates both amylin- and Calcr-expressing neurons, and leads to a recovery of Amylin mRNA expression. Chemogenetic activation of amylin neurons increases and molecular knockdown of either amylin or Calcr attenuates contact-seeking behavior, respectively. Our data provide evidence in support of a previously postulated origin of social affiliation in mammals.

Dorsal Bed Nucleus of the Stria Terminalis-Subcortical Output Circuits Encode Positive Bias in Pavlovian Fear and Reward

Opposite emotions like fear and reward states often utilize the same brain regions. The bed nucleus of the stria terminalis (BNST) comprises one hub for processing fear and reward processes. However, it remains unknown how dorsal BNST (dBNST) circuits process these antagonistic behaviors. Here, we exploited a combined Pavlovian fear and reward conditioning task that exposed mice to conditioned tone stimuli (CS)s, either paired with sucrose delivery or footshock unconditioned stimuli (US). Pharmacological inactivation identified the dorsal BNST as a crucial element for both fear and reward behavior. Deep brain calcium imaging revealed opposite roles of two distinct dBNST neuronal output pathways to the periaqueductal gray (PAG) or paraventricular hypothalamus (PVH). dBNST neural activity profiles differentially process valence and Pavlovian behavior components: dBNST-PAG neurons encode fear CS, whereas dBNST-PVH neurons encode reward responding. Optogenetic activation of BNST-PVH neurons increased reward seeking, whereas dBNST-PAG neurons attenuated freezing. Thus, dBNST-PVH or dBNST-PAG circuitry encodes oppositely valenced fear and reward states, while simultaneously triggering an overall positive affective response bias (increased reward seeking while reducing fear responses). We speculate that this mechanism amplifies reward responding and suppresses fear responses linked to BNST dysfunction in stress and addictive behaviors.

The Central Inflammatory Network: A Hypothalamic fMRI Study of Experimental Endotoxemia in Humans

INTRODUCTION

Inflammation is a mechanism of the immune system that is part of the reaction to pathogens or injury. The central nervous system closely regulates inflammation via neuroendocrine or direct neuroimmune mechanisms, but our current knowledge of the underlying circuitry is limited. Therefore, we aimed to identify hypothalamic centres involved in sensing or modulating inflammation and to study their association with known large-scale brain networks.

METHODS

Using high-resolution functional magnetic resonance imaging (fMRI), we recorded brain activity in healthy male subjects undergoing experimental inflammation from intravenous endotoxin. Four fMRI runs covered key phases of the developing inflammation: pre-inflammatory baseline, onset of endotoxemia, onset of pro-inflammatory cytokinemia, and peak of pro-inflammatory cytokinemia. Using masked independent component analysis, we identified functionally homogeneous subregions of the hypothalamus, which were further tested for changes in functional connectivity during inflammation and for temporal correlation with tumour necrosis factor and adrenocorticotropic hormone serum levels. We then studied the connection of these inflammation-associated hypothalamic subregions with known large-scale brain networks.

RESULTS

Our results show that there are at least 6 hypothalamic subregions associated with inflammation in humans including the paraventricular nucleus, supraoptic nucleus, dorsomedial hypothalamus, bed nucleus of the stria terminalis, lateral hypothalamic area, and supramammillary nucleus. They are functionally embedded in at least 3 different large-scale brain networks, namely a medial frontoparietal network, an occipital-pericentral network, and a midcingulo-insular network.

CONCLUSION

Measuring how the hypothalamus detects or modulates systemic inflammation is a first step to understand central nervous immunomodulation.

Corticotropin releasing factor and norepinephrine related circuitry changes in the bed nucleus of the stria terminalis in stress and alcohol and substance use disorders

Alcohol Use Disorder (AUD) affects around 14.5 million individuals in the United States, with Substance Use Disorder (SUD) affecting an additional 8.3 million individuals. Relapse is a major barrier to effective long-term treatment of this illness with stress often described as a key trigger for a person with AUD or SUD to relapse during a period of abstinence. Two signaling molecules, norepinephrine (NE) and corticotropin releasing factor (CRF), are released during the stress response, and also play important roles in reward behaviors and the addiction process. Within the addiction literature, one brain region in which there has been increasing research focus in recent years is the bed nucleus of the stria terminalis (BNST). The BNST is a limbic structure with numerous cytoarchitecturally and functionally different subregions that has been implicated in drug-seeking behaviors and stress responses. This review focuses on drug and stress-related neurocircuitry changes in the BNST, particularly within the CRF and NE systems, with an emphasis on differences and similarities between the major dorsal and ventral BNST subregions.

Efferent and Afferent Connections of Neuropeptide Y Neurons in the Nucleus Accumbens of Mice

Neuropeptide Y (NPY) is a neural peptide distributed widely in the brain and has various functions in each region. We previously reported that NPY neurons in the nucleus accumbens (NAc) are involved in the regulation of anxiety behavior. Anterograde and retrograde tracing studies suggest that neurons in the NAc project to several areas, such as the lateral hypothalamus (LH) and ventral pallidum (VP), and receive afferent projections from the cortex, thalamus, and amygdala. However, the neural connections between accumbal NPY neurons and other brain areas in mice remain unclear. In this study, we sought to clarify these anatomical connections of NPY neurons in the NAc by investigating their neural outputs and inputs. To selectively map NPY neuronal efferents from the NAc, we injected Cre-dependent adeno-associated viruses (AAVs) into the NAc of NPY-Cre mice. This revealed that NAc NPY neurons exclusively projected to the LH. We confirmed this by injecting cholera toxin b subunit (CTb), a retrograde tracer, into the LH and found that approximately 7–10% of NPY neurons in the NAc were double-labeled for mCherry and CTb. Moreover, retrograde tracing using recombinant rabies virus (rRABV) also identified NAc NPY projections to the LH. Finally, we investigated monosynaptic input to the NPY neurons in the NAc using rRABV. We found that NPY neurons in the NAc received direct synaptic connections from the midline thalamic nuclei and posterior basomedial amygdala. These findings provide new insight into the neural networks of accumbal NPY neurons and should assist in elucidating their functional roles.

Understanding the Significance of the Hypothalamic Nature of the Subthalamic Nucleus

The subthalamic nucleus (STN) is an essential component of the basal ganglia and has long been considered to be a part of the ventral thalamus. However, recent neurodevelopmental data indicated that this nucleus is of hypothalamic origin which is now commonly acknowledged. In this work, we aimed to verify whether the inclusion of the STN in the hypothalamus could influence the way we understand and conduct research on the organization of the whole ventral and posterior diencephalon. Developmental and neurochemical data indicate that the STN is part of a larger glutamatergic posterior hypothalamic region that includes the premammillary and mammillary nuclei. The main anatomic characteristic common to this region involves the convergent cortical and pallidal projections that it receives, which is based on the model of the hyperdirect and indirect pathways to the STN. This whole posterior hypothalamic region is then integrated into distinct functional networks that interact with the ventral mesencephalon to adjust behavior depending on external and internal contexts.

Enhanced Synaptic Transmission in the Extended Amygdala and Altered Excitability in an Extended Amygdala to Brainstem Circuit in a Dravet Syndrome Mouse Model

Dravet syndrome (DS) is a developmental and epileptic encephalopathy with an increased incidence of sudden death. Evidence of interictal breathing deficits in DS suggests that alterations in subcortical projections to brainstem nuclei may exist, which might be driving comorbidities in DS. The aim of this study was to determine whether a subcortical structure, the bed nucleus of the stria terminalis (BNST) in the extended amygdala, is activated by seizures, exhibits changes in excitability, and expresses any alterations in neurons projecting to a brainstem nucleus associated with respiration, stress response, and homeostasis. Experiments were conducted using F1 mice generated by breeding 129.Scn1a+/- mice with wild-type C57BL/6J mice. Immunohistochemistry was performed to quantify neuronal c-fos activation in DS mice after observed spontaneous seizures. Whole-cell patch-clamp and current-clamp electrophysiology recordings were conducted to evaluate changes in intrinsic and synaptic excitability in the BNST. Spontaneous seizures in DS mice significantly enhanced neuronal c-fos expression in the BNST. Further, the BNST had altered AMPA/NMDA postsynaptic receptor composition and showed changes in spontaneous neurotransmission, with greater excitation and decreased inhibition. BNST to parabrachial nucleus (PBN) projection neurons exhibited intrinsic excitability in wild-type mice, while these projection neurons were hypoexcitable in DS mice. The findings suggest that there is altered excitability in neurons of the BNST, including BNST-to-PBN projection neurons, in DS mice. These alterations could potentially be driving comorbid aspects of DS outside of seizures, including respiratory dysfunction and sudden death.

Resting-state causal connectivity of the bed nucleus of the stria terminalis in panic disorder

Panic disorder (PD) is associated with anticipatory anxiety, a sustained threat response that appears to be related to the bed nucleus of the stria terminalis (BNST). Individuals with panic disorder may demonstrate significant differences in causal connectivity of the BNST in comparison to healthy controls. To test this hypothesis, resting-state functional magnetic resonance imaging (fMRI) was used to identify aberrant causal connectivity of the BNST in PD patients. 19 PD patients and 18 healthy controls (HC) matched for gender, age and education were included. Granger causality analysis (GCA) utilizing the BNST as a seed region was used to investigate changes in directional connectivity. Relative to healthy controls, PD patients displayed abnormal directional connectivity of the BNST including enhanced causal connectivity between the left parahippocampal gyrus and left BNST, the right insula and the right BNST, the left BNST and the right dorsolateral prefrontal cortex (dlPFC) and right BNST to the left and right dlPFC. Furthermore, PD patients displayed weakened causal connectivity between the right dlPFC and the left BNST, the left dlPFC and the right BNST, the left BNST and the left dorsomedial prefrontal cortex (dmPFC), right insula, right fusiform, and right BNST to the right insula. The results suggest that PD strongly correlates with increased causal connectivity between emotional processing regions and the BNST and enhanced causal connectivity between the BNST and cognitive control regions.