Biology subjects

Bains, J. S.

Publications and source records attributed to Bains, J. S..

18 recordsLinked to original sources

bioRxiv2026

Exercise Leverages a Post-Stress Therapeutic Window in Hypothalamic CRH Neurons to Enable Recovery from Threat Sensitization

Exercise provides a range of benefits for physical and mental health. It relieves stress, yet paradoxically, it recruits the bodys stress response system. Here we show that activation of corticotropin-releasing hormone cells of the paraventricular nucleus of the hypothalamus (CRHPVN) and the endocrine arm of the stress axis is necessary, but not sufficient for the beneficial effects of exercise. Specifically, glucocorticoids act synergistically with brain-derived neurotrophic factor (BDNF) on CRHPVN cells during exercise to reverse behavioral and synaptic sensitization after stress. In the absence of exercise, optogenetic activation of the tropomyosin-related kinase B (TrkB) receptor after stress is sufficient to reverse behavioral sensitization and synaptic metaplasticity. Our findings reveal a novel, time-sensitive mechanism by which exercise alleviates the impact of acute stress.

neuroscience↗

bioRxiv2025

Hypothalamic CRH neurons gate rapid social appraisal of conspecifics

Successful navigation of the social environment requires rapid evaluation of conspecifics to distinguish safe from threatening encounters. While the corticotropin-releasing hormone neurons in the paraventricular nucleus of the hypothalamus (CRHPVN) are well known for orchestrating endocrine stress responses, their role in real-time social appraisal is unknown. Here, using fibre photometry and optogenetics during ethologically relevant social interactions, we show that CRHPVN neurons exhibit a rapid, transient increase in activity that precedes sniffing, an investigative behaviour through which mice gather social information. This transient signal scales with social context: it is heightened during interactions with unfamiliar and aggressive conspecifics and significantly reduced toward familiar partners. Inhibiting these neurons selectively diminished anogenital sniffing, demonstrating their necessity for optimal social evaluation. Strikingly, across repeated exposures to the same conspecific, behavioural investigation declined while CRHPVN activity remained robust, revealing a dissociation between neuronal and behavioural habituation. This persistence suggests that CRHPVN neurons encode stable neural representation of threat during social encounters. Together, our findings identify CRHPVN neurons as a fast, integrative node linking endocrine stress control to rapid social decision-making.

neuroscience↗

bioRxiv2025

The sodium channel SCN2A regulates cortical excitatory and inhibitory neurogenesis

Voltage-gated sodium channels regulate neuronal excitability and synaptic transmission in the postnatal and adult brain. The gene SCN2A, encoding the sodium channel Nav1.2, regulates synaptic development and variants in SCN2A are associated with autism spectrum disorders (ASD) and a broad spectrum of epilepsy phenotypes, including early-onset developmental and epileptic encephalopathies. The expression pattern of SCN2A begins during prenatal cortical development, prior to the onset of synaptic transmission, but it is unknown whether SCN2A regulates early cortical development through mechanisms independent of synaptic transmission. Here we reveal that isogenic and ASD patient-derived human forebrain organoids modelling a loss of SCN2A function display impaired excitatory and inhibitory neurogenesis, leading to a developmental imbalance. Unexpectedly, we find precocious generation of cortical inhibitory neurons is driven by elevated Sonic hedgehog signaling and is reversible through pharmacological inhibition. Functionally, these developmental phenotypes arise due to Nav1.2-dependent sodium channel dysfunction and reduced action potential generation, leading to abnormal neuronal network activity. Our results identify a mechanism for cortical excitatory and inhibitory neurogenesis involving SCN2A, and reveal that early neurogenesis deficits precede postnatal neural circuit dysfunction in SCN2A-associated disorders.

neuroscience↗

bioRxiv2025

Psilocybin induces sex- and context-specific recruitment of the stress axis

Psychedelics have reemerged as potential treatments for mental health disorders, yet their impact on stress-related brain regions remains poorly understood. Here, we provide the first real-time, in vivo evidence of psilocybin-induced neuronal activation, specifically in hypothalamic corticotropin-releasing hormone neurons. Notably, psilocybin elicited more pronounced responses in female mice and produced context-related alterations in threat assessment. Our findings provide valuable insight into the impact of psychedelics on a key stress center in the brain.

neuroscience↗

bioRxiv2023

Impact and role of hypothalamic corticotropin releasing hormone neurons in withdrawal from chronic alcohol consumption in female and male mice.

Worldwide, alcohol use and abuse are a leading risk of mortality, causing 5.3% of all deaths (W.H.O., 2022). The endocrine stress system, initiated by the peripheral release of corticotropin releasing hormone (CRH) from primarily glutamatergic neurons in the paraventricular nucleus of the hypothalamus (PVN), is profoundly linked with alcohol use, abuse, and relapse (Blaine & Sinha, 2017). These PVN CRH-releasing (PVNCRH) neurons are essential for peripheral and central stress responses (Rasiah et al., 2023), but little is known about how alcohol affects these neurons. Here, we show that two- bottle choice alcohol consumption blunts the endocrine mediated corticosterone response to stress during acute withdrawal in female mice. Conversely, using slice electrophysiology, we demonstrate that acute withdrawal engenders a hyperexcitable phenotype of PVNCRH neurons in females that is accompanied by increased glutamatergic transmission in both male and female mice. Only male mice show a concurrent increase in GABAergic synaptic transmission. We then tested whether chemogenetic inhibition of PVNCRH neurons would restore stress response in female mice with a history of alcohol drinking in the looming disc test, which mimics an approaching predator threat. Accordingly, inhibition of PVNCRH neurons reduced active escape in hM4Di alcohol history mice only. This study indicates that stress responsive PVNCRH neurons in females are particularly affected by a history of alcohol consumption. Interestingly, women have indicated an increase in heavy alcohol use to cope with stress (Rodriguez et al., 2020), perhaps pointing to a potential underlying mechanism in alcohol mediated changes to PVNCRH neurons that alter stress response.

neuroscience↗

bioRxiv2023

Novel psilocin prodrugs with altered pharmacological properties as candidate therapies for treatment-resistant anxiety disorders

The psychedelic compound psilocybin has shown therapeutic benefit in the treatment of numerous psychiatric diseases. A recent randomized clinical trial conducted at Johns Hopkins Bayview Medical Center demonstrated the efficacy of psilocybin-assisted therapy in the treatment of Major Depressive Disorder (MDD). Similarly, a phase IIb study evaluating psilocybin-assisted therapy for treatment-resistant depression (TRD) presented statistically meaningful and long-term reduction in depressive symptoms. Also, many studies have reported the successful treatment of severe anxiety after a single oral dose of psilocybin, especially in patients struggling with cancer-related distress (CRD). Despite these compelling clinical results, concerns regarding the duration of the psychedelic experience produced by psilocybin pose a significant barrier to its widespread therapeutic application. Psilocybin, derived from magic mushrooms is the naturally occurring prodrug of the neuroactive compound psilocin. When orally administered, exposure to the acidic gastrointestinal (GI) environment together with enzymatic processing by intestinal and hepatic alkaline phosphatase lead to the dephosphorylation of psilocybin producing elevated levels of systemic psilocin. These plasma levels are detectable up to 24 h and produce a psychoactive episode lasting as long as 6 h post-ingestion. In order to positively modify the kinetics of the acute psychedelic response, we have engineered a library of novel prodrug derivatives (NPDs) of psilocin, introducing a diversity of alternative metabolically cleavable moieties modified at the 4-carbon position of the core indole ring. This library consists of twenty-eight unique compounds represented by nine distinct prodrug classes. Each molecule was screened in vitro for metabolic stability using isolated human serum, and human cellular fractions derived from liver and intestinal tissues. This screen revealed fifteen prodrugs that produced measurable levels of psilocin in vitro, with ester and thiocarbonate-based prodrug derivatives significantly represented. These fifteen NPDs were further evaluated for pharmacokinetic (PK) profiles in mice, assessing plasma levels of both residual prodrug and resultant psilocin. PK results confirmed the efficiency of ester and thiocarbonate-based prodrug metabolism upon oral and intravenous administration, achieving levels reduced, albeit comparable to levels of psilocybin-derived psilocin. Of note, almost all NPDs tested maintained reduced overall exposure of psilocin relative to psilocybin, with no measurable levels detected at 24 h post-dose. Finally, all NPDs were screened for CNS bioavailability in healthy mice using the Head Twitch Response (HTR), a behavioural biomarker of 5-HT2A receptor stimulation and an established proxy for psychoactive potential. Interestingly, five NPDs produced peak HTR that approached or exceeded levels induced by an equivalent dose of psilocybin. Among these bioactive prodrugs, an ester-based and thiocarbonate-based molecule produced long-term anxiolytic benefit in chronically stressed mice evaluated in the marble burying psychiatric model. Overall, this screening campaign identified novel candidate prodrugs of psilocin with altered metabolic profiles and reduced pharmacological exposure, potentially attenuating the duration of the psychedelic response. These molecules still maintained the long-term psychiatric and physiological benefits characteristic of psilocybin therapy. Additionally, these modified parameters also offer the opportunity for altered routes of administration bypassing conventional oral dosing.

pharmacology and toxicology↗

bioRxiv2023

Optogenetic recruitment of hypothalamic corticotrophin-releasing-hormone (CRH) neurons reduces motivational drive

Impaired motivational drive is a key feature of depression. Chronic stress is a known antecedent to the development of depression in humans and depressive-like states in animals. Whilst there is a clear relationship between stress and motivational drive, the mechanisms underpinning this association remain unclear. One hypothesis is that the endocrine system, via corticotropin-releasing hormone (CRH) in the paraventricular nucleus of the hypothalamus (PVN; PVNCRH), initiates a hormonal cascade resulting in glucocorticoid release, and that excessive glucocorticoids change brain circuit function to produce depression-related symptoms. Another, mostly unexplored hypothesis is that the direct activity of PVNCRH neurons and their input to other stress- and reward-related brain regions drives these behaviours. To further understand the direct involvement of PVNCRH neurons in motivation, we used optogenetic stimulation to activate these neurons one hour/day for 5 consecutive days and showed increased acute stress-related behaviours and long-lasting deficits in the motivational drive for sucrose. This was associated with increased Fos-protein expression in the lateral hypothalamus (LH). Direct stimulation of the PVNCRH inputs in the LH produced a similar pattern of effects on sucrose motivation. Together, these data suggest that PVNCRH neuronal activity may be directly responsible for changes in motivational drive and that these behavioural changes may, in part, be driven by PVNCRH synaptic projections to the LH.

neuroscience↗

bioRxiv2022

Hypothalamic vasopressin sex differentiation is established during embryonic neurogenesis

Arginine vasopressin (AVP) is a conserved sexually dimorphic system regulating behaviors and physiologies. Decades of research concludes that AVP sex differentiation in mice occurs around birth when a gonadal surge of testosterone is converted to estrogen in male sexual dimorphic brain regions. We discovered that AVP neurons in the murine hypothalamus are sexually dimorphic much earlier than this surge, with male mice displaying more AVP neurons than females during neurogenesis at E11. In utero exposure to a pan-ER antagonist blocked AVP masculinization in males, whereas embryonic exogenous 17{beta}-estradiol or xenoestrogen bisphenol A (BPA) masculinized female AVP neurons, causing permanent masculinization effects on adult female AVP cell numbers, projections and intrinsic neuronal properties. Our data reveal that sexual dimorphism of hypothalamic AVP neurons is present from the earliest stages of their differentiation and challenges current dogma that masculinization of the male brain occurs around birth. One-Sentence SummarySexual dimorphism of hypothalamic vasopressin is established during neurogenesis and exposure to the xenoestrogen bisphenol A during pregnancy induces masculinization of female brains

neuroscience↗

bioRxiv2022

Disruption of Tonic Endocannabinoid Signaling Triggers the Generation of a Stress Response

Endocannabinoid (eCB) signalling gates many aspects of the stress response, including the hypothalamic-pituitary-adrenal (HPA) axis. The HPA axis is controlled by corticotropin releasing hormone (CRH) producing neurons in the paraventricular nucleus of the hypothalamus (PVN). Disruption of eCB signalling increases drive to the HPA axis, but the mechanisms subserving this process are poorly understood. Using an array of cellular, endocrine and behavioral readouts associated with activation of CRH neurons in the PVN, we evaluated the contributions of tonic eCB signaling to the generation of a stress response. The CB1 receptor antagonist/inverse agonist AM251, neutral antagonist NESS243, and NAPE PLD inhibitor LEI401 all uniformly increased c-fos in the PVN, unmasked stress-linked behaviors, such as grooming, and increased circulating CORT, recapitulating the effects of stress. Similar effects were also seen after direct administration of AM251 into the PVN, while optogenetic inhibition of PVN CRH neurons ameliorated stress-like behavioral changes produced by disruption of eCB signaling. These data indicate that under resting conditions, constitutive eCB signaling restricts activation of the HPA axis through local regulation of CRH neurons in the PVN.

neuroscience↗

bioRxiv2022

Particle-Swarm Based Modelling Reveals Two Distinct Classes of CRHPVN Neurons

Electrophysiological recordings can provide detailed information of single neurons dynamical features and shed light into their response to stimuli. Unfortunately, rapidly modeling electrophysiological data for inferring network-level behaviours remains challenging. Here, we investigate how modeled single neuron dynamics lead to network-level responses in the paraventricular nucleus of the hypothalamus (PVN), a critical nucleus for the mammalian stress response. Recordings of corticotropinreleasing hormone neurons from the PVN (CRHPVN) were performed using whole-cell current-clamp. These, neurons, which initiate the endocrine response to stress, were rapidly and automatically fit to a modified Adaptive Exponential Integrate and Fire model (AdEx) with Particle Swarm Optimization (PSO). All CRHPVN neurons were accurately fit by the AdEx model with PSO. Multiple sets of parameters were found that reliably reproduced current-clamp traces for any single neuron. Despite multiple solutions, the dynamical features of the models such as the rheobase current levels, fixed points, and bifurcations, were shown to be stable across fits. We found that CRHPVN neurons can be divided into two sub-types according to their bifurcation at the onset of firing: saddles (integrators) and sub-critical Hopf (resonators). We constructed networks of these fit CRHPVN model neurons to investigate the network level responses of CRHPVN neurons. We found that CRHPVN-resonators maintain baseline firing in networks even when all inputs are inhibitory. The dynamics of a small subset of CRHPVN neurons may be critical to maintaining a baseline firing tone in the PVN. Key PointsO_LICorticotropin-releasing hormone neurons (CRHPVN) in the paraventricular nucleus of the hypothalamus act as the final neural controllers of the stress response. C_LIO_LIWe developed a rapid computational modeling platform that uses Particle-Swarm Optimization to rapidly and accurately fit biophysical neuron models. C_LIO_LIA model was fit to each patched neuron without the use of dynamic clamping, or other procedures requiring sophisticated inputs and fitting procedures. Any neuron undergoing standard current clamping for a few minutes can be fit by this procedure C_LIO_LIThe dynamical analysis of the modeled neurons shows thatCRHPVN comes in two specific flavours: CRHPVN-resonators and CRHPVN-integrators. C_LIO_LINetwork simulations show thatCRHPVN-resonators are critical to retaining the baseline firing rate of the entire network of CRHPVN neurons as these cells can fire rebound spikes and bursts in the presence of strong inhibitory synaptic input. C_LI

neuroscience↗

bioRxiv2022

Chronic Alcohol Consumption Alters Home-Cage Behaviors and Responses to Ethologically Relevant Predator Tasks in Mice

Alcohol use disorders (AUD) are the most prevalent substance use disorders worldwide. Considering recent reports indicating an increase in alcohol use particularly in females, it is vital to understand how alcohol history impacts behavior. Animal model research on withdrawal-associated affective states tends to focus on males, forced alcohol paradigms, and a few traditional anxiety/stress tests. While this has been essential, heavy alcohol use triggers adverse withdrawal-related affective states that can influence how people respond to a large variety of life events and stressors. To this end, we show that behaviors in the home-cage, open field, looming disc, and robogator predator threat task, which vary in task demand and intensity, are altered in mice with a history of voluntary alcohol consumption. In alcohol-exposed males, behaviors in the home cage, a low anxiety baseline environment, suggest increased vigilance/exploration. However, in the open field and robogator task, which induce heightened arousal and task demands, a more hesitant/avoidant phenotype is seen. Female alcohol mice show no behavioral alterations in the home cage and open field test, however, in the looming disc task, which mimics an overhead advancing predator and forces a behavioral choice, we see greater escape responses compared to water controls, indicative of active stress coping behaviors. This suggests females may begin to show alcohol-induced alterations as task demands increase. To date, few drugs have advanced past clinical trials for the treatment of AUD, and those that have are predominately used in life-threatening situations only. No treatments exist for ameliorating negative withdrawal related states, which could aid in harm reduction related to heavy alcohol use. Understanding how withdrawal alters a variety of behavioral responses that are linked to stress coping can widen our understanding of alcohol abuse and lead us closer to better therapeutics to help individuals with AUD.

neuroscience↗

bioRxiv2021

A genetically encoded fluorescent biosensor for extracellular L-lactate

To enable investigations of the emerging roles of cell-to-cell shuttling of L-lactate, we have developed an intensiometric green fluorescent genetically encoded biosensor for extracellular L-lactate. We demonstrate that this biosensor, designated eLACCO1.1, enables minimally invasive cellular resolution imaging of extracellular L-lactate in cultured mammalian cells and brain tissue.

molecular biology↗

bioRxiv2020

Spatiotemporal chloride dynamics in hypothalamic CRHPVN neurons

Chloride (Cl-) dynamics shape inhibitory neurotransmission in the brain. In the hypothalamus, GABA signalling onto corticotropin-releasing hormone (CRHPVN) neurons can switch from inhibitory to excitatory during stress. Although Cl- fluctuations mediate this stress-dependent shift in GABA signalling, the underlying Cl- dynamics are poorly understood. Here, using a novel optogenetic strategy to load intracellular Cl- using halorhodopsin, we demonstrate that KCC2 rapidly restores Cl- setpoints in CRHPVN neurons from naive animals, but that this process is slowed following stress. Further, we report that somatic Cl- homeostasis remains intact after stress. Our results strongly support the idea that KCC2 functions primarily to maintain Cl- setpoints and that inhibitory synapses onto dendritic and somatic compartments of CRHPVN neurons are differentially regulated during stress.

neuroscience↗

bioRxiv2020

Obesity-induced astrocyte dysregulation of heterosynaptic plasticity within the orbitofrontal cortex

SO_SCPLOWUMMARYC_SCPLOWOverconsumption of highly palatable, energy dense food is considered a key driver of the obesity pandemic. The orbitofrontal cortex (OFC) is critical for reward valuation of gustatory signals, yet how the OFC adapts to obesogenic diets is poorly understood. Here we show that extended access to a cafeteria diet impairs astrocyte glutamate clearance, which leads to a heterosynaptic depression of GABA transmission onto pyramidal neurons of the OFC. This decrease in GABA tone is due to an increase in extrasynaptic glutamate, which acts via metabotropic glutamate receptors to liberate endocannabinoids. This impaired the induction of endocannabinoid-mediated long-term plasticity. In obese rats, this cascade of synaptic impairments was rescued by restoring astrocyte glutamate transport with the nutritional supplement, N-acetylcysteine. Together, our findings indicate that obesity targets astrocytes to disrupt the delicate balance between excitatory and inhibitory transmission in the OFC. HO_SCPLOWIGHLIGHTSC_SCPLOWO_LIDiet-induced obesity induces hypertrophy of astrocytes and impairs their ability to transport glutamate. C_LIO_LIFailure of astrocytes to clear extrasynaptic glutamate drives endocannabinoid-mediated inhibitory long-term depression of principal output neurons in the OFC. C_LIO_LIAstrocytic glutamate transporter function is restored with NAC, which rescues the synaptic deficits. C_LI

neuroscience↗

bioRxiv2020

Sex-specific vasopressin signaling buffers stress-dependent synaptic changes in female mice

In many species, social networks provide benefit for both the individual and the collective. In addition to transmitting information to others, social networks provide an emotional buffer for distressed individuals. Our understanding about the cellular mechanisms that contribute to buffering is poor. Stress has consequences for the entire organism, including a robust change in synaptic plasticity at glutamate synapses onto corticotropin-releasing hormone (CRH) neurons in the paraventricular nucleus of the hypothalamus (PVN). In females, however, this stress-induced metaplasticity is buffered by the presence of a naive partner. This buffering may be due to discrete behavioral interactions, signals in the context in which the interaction occurs (i.e. olfactory cues), or it may be influenced by local signaling events in the PVN. Here, we show that local vasopressin (VP) signaling in PVN buffers the short-term potentiation (STP) at glutamate synapses after stress. This social buffering of metaplasticity, which requires the presence of another individual, was prevented by pharmacological inhibition of the VP 1a receptor in female mice. Exogenous VP mimicked the effects of social buffering and reduced STP in CRHPVN neurons from females but not males. These findings implicate VP as a potential mediator of social buffering in female mice. Significance StatementIn many organisms, including rodents and humans, social groups are beneficial to overall health and well-being. Moreover, it is through these social interactions that the harmful effects of stress can be mitigated--a phenomenon known as social buffering. In the present study, we describe a critical role for the neuropeptide vasopressin in social buffering of synaptic metaplasticity in stress-responsive corticotropin-releasing hormone neurons in female mice. These effects of vasopressin do not extend to social buffering of stress behaviors, suggesting this is a very precise and local form of sex-specific neuropeptide signaling.

neuroscience↗

bioRxiv2020

Adaptive synaptic plasticity maintains CRH neuron output during chronic glucocorticoid exposure

An increase in circulating glucocorticoids (CORT) is an essential part of the response to stress. Sustained elevations of CORT, however, have dramatic consequences on behavior, endocrine systems and peripheral organs. Critically, they dampen the endocrine response to acute challenges and decrease intrinsic excitability of corticotropin-releasing hormone neurons in the paraventricular nucleus (CRHPVN), suggesting key circuits may be less responsive to stress. Here, we make the surprising discovery that CRHPVN neurons harness a form of adaptive synaptic scaling to escape the persistent negative feedback pressure from CORT and maintain stable output in vivo. Specifically, there is an increase in glutamatergic drive to these cells that is mediated by a postsynaptic, multiplicative increase in synaptic strength. These findings suggest that dysfunctions associated with chronic stress may not be due to the primary actions of CORT, but instead reflect the emergence of synaptic adaptations as networks seek to re-establish intrinsic activity setpoints.

neuroscience↗

bioRxiv2020

A ventral striatal-orexin/hypocretin circuit modulates approach but not consumption of food.

Reward-seeking involves the engagement and computation of multiple physiological and motivational parameters. The lateral hypothalamus (LH) is a necessary node in the circuits that control food-seeking and motivation. One group of cells that plays an important yet incompletely understood role in these processes are the orexin/hypocretin (OX/HT) neurons. OX/HT cells are located exclusively within the LH and are implicated in feeding, arousal, and reward-seeking behavior. Importantly, the role of OX/HT neurons in consummatory versus reward-seeking actions is not fully defined, nor are the circuits that control the activity of these neurons under different behavioral states. Here we show that OX/HT neurons respond in real time to food presentation and that this response is modulated by differences in metabolic state. We observed increased OX/HT neuron activity on approach to food, but this activity trended towards pre-approach levels by the start of the consummatory phase. Next, we studied ventrostriatopallidal (VSP) inputs to the OX/HT neurons. Using optogenetics and cell type-specific electrophysiology, we found that ventral pallidum inputs onto OX/HT neurons exert strong inhibitory (and weak excitatory) effects whereas the lateral nucleus accumbens shell provides weaker direct inhibitory connections with OX/HT neurons. These findings reveal that the activity of OX/HT neurons is strongly modulated by metabolic and hedonic state. Further, OX/HT neurons is primarily associated with food approach and that the effect of VSP-terminal output is to suppress OX/HT activity.

neuroscience↗

bioRxiv2018

Activation of lateral hypothalamic group III mGluRs suppresses drug-seeking following abstinence and cocaine-associated increases in excitatory drive to orexin/hypocretin cells

The perifornical/lateral hypothalamic area (LHA) orexin (hypocretin) system is involved in drug-seeking behavior elicited by drug-associated stimuli. Cocaine exposure is associated with presynaptic plasticity at LHA orexin cells such that excitatory input to orexin cells is enhanced, both acutely and into withdrawal. These changes may augment orexin cell reactivity to drug-related cues during abstinence and contribute to relapse-like behavior. Studies in hypothalamic slices from drug-naive animals indicate that agonism of group III metabotropic glutamate receptors (mGluRs) reduces presynaptic glutamate release onto orexin cells. Therefore, we examined the group III mGluR system as a potential target to reduce orexin cell excitability in-vivo, and tested whether activating these receptors could normalize orexin cell activity following cocaine and reduce cocaine-seeking elicited by drug-associated stimuli during abstinence. First, we verified that group III mGluRs regulate orexin cell activity in vivo by showing that intra-LHA infusions of the selective agonist L-(+)-2-Amino-4-phosphonobutyric acid (L-AP4) reduces Fos expression in orexin cells following 24h food deprivation. Next, we extended these findings to show that intra-LHA L-AP4 infusions reduced discriminative stimulus-driven cocaine-seeking following withdrawal. L-AP4 had no effect on general motor activity of sucrose self-administration. Finally, using whole-cell patch clamp recordings from identified orexin cells in orexin-GFP transgenic mice, we show that enhanced presynaptic drive to orexin cells persists for up to 14d into withdrawal and that this plasticity is normalized by L-AP4. L-AP4 had no effect on measures of postsynaptic plasticity in cocaine-exposed animals. Together, these data indicate that agonism of LHA group III mGluRs reduces orexin cell activity in-vivo and is an effective strategy to suppress cocaine-seeking behavior following withdrawal. These effects are likely mediated, at least in part, by normalization of presynaptic plasticity at orexin cells that occurs as a result of cocaine exposure.

neuroscience↗