Management of Acute Stress Reactions in the Military: A Stepped Care Approach.

PURPOSE OF THE REVIEW: This review highlights knowledge gaps surrounding the development and use of interventions for Acute Stress Reactions (ASRs). First, we propose that a stepped care approach to intervention for ASR be developed and utilized in military operational environments. A stepped care approach would include detection and assessment, followed by behavioral intervention, and then medication intervention for ASRs. Second, we discuss potential strategies that can be taken for the development of safe and effective ASR medications. RECENT FINDINGS: ASRs commonly occur in operational environments, particularly in military populations. ASRs impact the safety and performance of individual service members and teams, but there are currently limited options for intervention. Efforts to improve ASR detection and assessment, and development and delivery of ASR interventions for implementation in operational environments, will be critical to maintaining the safety and performance of service members.

Serotonin modulates an inhibitory input to the central amygdala from the ventral periaqueductal gray.

Fear is an adaptive state that drives defensive behavioral responses to specific and imminent threats. The central nucleus of the amygdala (CeA) is a critical site of adaptations that are required for the acquisition and expression of fear, in part due to alterations in the activity of inputs to the CeA. Here, we characterize a novel GABAergic input to the CeA from the ventral periaqueductal gray (vPAG) using fiber photometry and ex vivo whole-cell slice electrophysiology combined with optogenetics and pharmacology. GABA transmission from this ascending vPAG-CeA input was enhanced by serotonin via activation of serotonin type 2 C (5HT2C) receptors. Results suggest that these receptors are presynaptic. Interestingly, we found that GABA release from the vPAG-CeA input is enhanced following fear learning via activation of 5HT2C receptors and that this pathway is dynamically engaged in response to aversive stimuli. Additionally, we characterized serotonin release in the CeA during fear learning and recall for the first time using fiber photometry coupled to a serotonin biosensor. Together, these findings describe a mechanism by which serotonin modulates GABA release from ascending vPAG GABA inputs to the CeA and characterize a role for this pathway in fear.

Acute sleep interventions as an avenue for treatment of trauma-associated disorders.

Scientific evidence that acute, posttrauma sleep disturbances (eg, nightmares and insomnia) can contribute significantly to the pathogenesis of trauma-induced disorders is compelling. Sleep disturbances precipitating from trauma are uniquely predictive of daytime posttrauma symptom occurrence and severity, as well as subsequent onset of mental health disorders, including post-traumatic stress disorder. Conversely, adequate sleep during the acute posttrauma period is associated with reduced likelihood of adverse mental health outcomes. These findings, which are broadly consistent with what is known about the role of sleep in the regulation of emotion, suggest that the acute posttrauma period constitutes a "window of opportunity" during which treatment of sleep disturbances may be especially effective for preventing or mitigating progression of aberrant psychophysiological processes. At this point, the weight of the scientific evidence supporting this possibility warrants initiation of clinical trials to confirm the benefits of targeted prophylactic sleep enhancement, and to establish treatment guidelines as appropriate. CITATION: Swift KM, Thomas CL, Balkin TJ, Lowery-Gionta EG, Matson LM. Acute sleep interventions as an avenue for treatment of trauma-associated disorders. J Clin Sleep Med. 2022;18(9):2291-2312.

Response and recovery of endocrine, behavioral, and neuronal morphology outcomes after different traumatic stressor exposures in male rats.

Preclinical models of organismal response to traumatic stress (threat of death or serious injury) can be monitored using neuroendocrine, behavioral, and structural metrics. While many rodent models of traumatic stress have provided a glimpse into select components of the physiological response to acute and chronic stressors, few studies have directly examined the potential differences between stressors and their potential outcomes. To address this gap, we conducted a multi-level comparison of the immediate and longer-term effects of two types of acute traumatic stressors. Adult male rats were exposed to either underwater trauma (UWT), predator exposure (PE), or control procedural handling conditions. Over the next 7 days, yoked cohorts underwent either serial blood sampling for neuroendocrine evaluation across the circadian cycle, or repeated behavioral testing in the elevated plus maze. In addition, a subset of brains from the latter cohort were assessed for dendritic spine changes in the prefrontal cortex and basolateral amygdala. We observed stressor-dependent patterns of response and recovery across all measures, with divergence between endocrine responses despite similar behavioral outcomes. These results demonstrate that different stressors elicit unique behavioral, neuroendocrine, and neuro-structural response profiles and suggest that specific stress models can be used to model desired responses for specific preclinical applications, such as evaluations of underlying mechanisms or therapeutic candidates.

Fear expression is reduced after acute and repeated nociceptin/orphanin FQ (NOP) receptor antagonism in rats: therapeutic implications for traumatic stress exposure.

RATIONALE: Evaluation of pharmacotherapies for acute stress disorder (ASD) or post-traumatic stress disorder (PTSD) is challenging due to robust heterogeneity of trauma histories and limited efficacy of any single candidate to reduce all stress-induced effects. Pursuing novel mechanisms, such as the nociceptin/orphanin FQ (NOP) system, may be a viable path for therapeutic development and of interest as it is involved in regulation of relevant behaviors and recently implicated in PTSD and ASD. OBJECTIVES: First, we evaluated NOP receptor antagonism on general behavioral performance and again following a three-species predator exposure model (Experiment 1). Then, we evaluated effects of NOP antagonism on fear memory expression (Experiment 2). METHODS: Adult, male rats underwent daily administration of NOP antagonists (J-113397 or SB-612,111; 0-20 mg/kg, i.p.) and testing in acoustic startle, elevated plus maze, tail-flick, and open field tests. Effects of acute NOP antagonism on behavioral performance following predator exposure were then assessed. Separately, rats underwent fear conditioning and were later administered SB-612,111 (0-3 mg/kg, i.p.) prior to fear memory expression tests. RESULTS: J-113397 and SB-612,111 did not significantly alter most general behavioral performance measures alone, suggesting minimal off-target behavioral effects of NOP antagonism. J-113397 and SB-612,111 restored performance in measures of exploratory behavior (basic movements on the elevated plus maze and total distance in the open field) following predator exposure. Additionally, SB-612,111 significantly reduced freezing behavior relative to control groups across repeated fear memory expression tests, suggesting NOP antagonism may be useful in dampening fear responses. Other measures of general behavioral performance were not significantly altered following predator exposure. CONCLUSIONS: NOP antagonists may be useful as pharmacotherapeutics for dampening fear responses to trauma reminders, and the present results provide supporting evidence for the implication of the NOP system in the neuropathophysiology of dysregulations in fear learning and memory processes observed in trauma- and stress-related disorders.

Heroin addiction engages negative emotional learning brain circuits in rats.

Opioid use disorder (OUD) is associated with the emergence of persistent negative emotional states during drug abstinence that drive compulsive drug taking and seeking. Functional magnetic resonance imaging (fMRI) in rats identified neurocircuits that were activated by stimuli that were previously paired with heroin withdrawal. The activation of amygdala and hypothalamic circuits was related to the degree of heroin dependence, supporting the significance of conditioned negative affect in sustaining compulsive-like heroin seeking and taking and providing neurobiological insights into the drivers of the current opioid crisis.

Repeated elevated plus maze trials as a measure for tracking within-subjects behavioral performance in rats (Rattus norvegicus).

The elevated plus maze (EPM) is routinely used in neuroscience research to evaluate emotional behavior in rodents by measuring general exploratory performance and avoidance of the aversive open arms of the maze. According to standard practice, behavior on the EPM is evaluated during a single trial to avoid the possibility of habituation to the apparatus that would result in lost sensitivity of key outcome measures. However, this possibility has not been systematically evaluated across repeated trials or across different environmental conditions. In the current study, we assessed within-subject behavior on the EPM in adult male rats over thirteen trials (tested twice weekly) repeated under identical conditions. We also assessed within-subject behavior on the EPM in adult male rats under dim (1 lux in the closed arm) and lit (246 lux in the closed arm) environmental conditions. We found that measures of general performance (basic movements and total distanced travelled throughout the maze) were stable across repeated trials and environmental conditions. We found that measures of open arm avoidance (distance travelled in, time spent in and entries in to the open arm) varied across trials and environmental conditions and were sensitive to the lighting conditions of the initial test. Though measures of open arm avoidance did show a linear trend indicative of habituation across repeated trials, this effect was variable across trials. Notably, preference for the open arm over the closed arm (measured as % of time spent in the open arm) assessed among individual animals occurred rarely and was never observed on the group level across the thirteen repeated trials. Together, these data demonstrate that measures of general performance such as basic movements and total distance traveled are robust to repeated testing and changing environmental lighting conditions. In contrast, measures of open arm avoidance show habituation with repeated testing and are sensitive to changing environmental lighting conditions. Based on these results, we suggest that within-subjects repeated testing on the EPM is valid in well-controlled studies that include an untreated control group to account for inter-trial variability and habituation.

GABA neurons of the ventral periaqueductal gray area modulate behaviors associated with anxiety and conditioned fear.

Emotional behavioral responses related to anxiety and fear comprise the negative valence systems domain as defined by the Research Domain Criteria (RDoC) approach to categorizing related emotional behavioral constructs that are compromised in mental health disorders. Here, we evaluate the role of GABA neurons of the ventral periaqueductal gray (vPAG) in emotional behavioral responses related to anxiety and fear using a chemogenetic approach in Vgat-ires-Cre mice. Functional inhibition of vPAG GABA neurons using selective expression of inhibitory Gi-coupled Designer Receptors Exclusively Activated by Designer Drugs (Gi-DREADDs) enhanced anxiety-like behavior in the light-dark exploration and open-field tests. Functional inhibition of vPAG GABA neurons during the acquisition of conditioned fear impaired later performance of conditioned fear responses to the fear-associated context. No effects on spontaneous freezing behavior, fear generalization, or conditioned fear responses to the fear-associated cue were observed. Together, these data suggest that activity of vPAG GABA neurons underlies emotional behavioral responses related to anxiety and conditioned fear. As such, vPAG GABA neurons are a common neurophysiological correlate of the negative valence system and dysregulation of this population may contribute to the etiology of mental health disorders in which the negative valence systems domain is compromised.

Chronic stress dysregulates amygdalar output to the prefrontal cortex.

Chronic stress contributes to the neuropathology of mental health disorders, including those associated with anxiety. The basolateral amygdala (BLA) coordinates emotional behavioral responses through glutamatergic outputs to downstream regions such as the prefrontal cortex (PFC), nucleus accumbens core (NAcc) and bed nucleus of the stria terminalis (BNST). We explored the effects of chronic stress on BLA outputs to the PFC, NAcc and BNST using slice electrophysiology combined with optogenetics in two inbred mouse strains with distinct stress-induced anxiety responses. We found that ten consecutive days of chronic restraint stress enhanced pre-synaptic glutamate release at BLA-to-PFC synapses in C57BL/6J mice, but reduced pre-synaptic glutamate release at these synapses in DBA/2J mice. To assess the behavioral relevance of enhanced glutamate output at BLA-to-PFC synapses, we approximated the effects of chronic stress on the BLA-PFC circuit using optogenetics. We found that photostimulation of the BLA-PFC circuit in unstressed C57BL/6J mice produced persistent (i.e., post-stimulation) increased anxiety-like behavior and hyperactivity in the elevated plus-maze - a profile consistent with prototypical behavioral responses of stressed C57BL/6J mice. These data demonstrate that chronic stress dysregulates the BLA-PFC circuit by altering pre-synaptic glutamate release from BLA outputs, and provide a mechanism by which chronic stress can lead to increased anxiety.

Compulsive-Like Sufentanil Vapor Self-Administration in Rats.

Opioid misuse is at historically high levels in the United States, with inhalation (ie, smoking and vaping) being one of the most common routes of consumption. We developed and validated a novel preclinical model of opioid self-administration by inhalation that does not require surgery and reliably produces somatic and motivational signs of dependence. Rats were trained to perform an operant response (nosepoke) to receive 10 s of vaporized sufentanil, a potent opioid, in 2 h daily sessions. Rats readily and concentration-dependently self-administered vaporized sufentanil. Rats exhibited a significant increase in responding for sufentanil when given the preferential µ-opioid receptor inverse agonist naloxone, suggesting the participation of µ-opioid receptors in the reinforcing properties of sufentanil vapor. Serum sufentanil concentrations significantly correlated with the number of sufentanil vapor deliveries. Rats that were given long access (LgA; 12 h/day) but not short access (ShA; 1 h/day) to vaporized sufentanil escalated their drug intake over time and exhibited both naloxone-precipitated somatic signs of opioid withdrawal and spontaneous withdrawal-induced mechanical hypersensitivity. After 6 months of forced drug abstinence, LgA rats returned to pre-escalation baseline levels of responding for sufentanil and mechanical sensitivity. Upon subsequent re-escalation (ie, after the return to extended access to sufentanil vapor), LgA rats again developed naloxone-precipitated somatic signs of withdrawal and spontaneous withdrawal-induced mechanical hypersensitivity. These findings demonstrate that the operant sufentanil vapor self-administration model has both face and construct validity and therefore will be useful for investigating the neurobiological basis of opioid addiction.

Chronic EtOH effects on putative measures of compulsive behavior in mice.

Addictions, including alcohol use disorders, are characterized by the loss of control over drug seeking and consumption, but the neural circuits and signaling mechanisms responsible for the transition from controlled use to uncontrolled abuse remain incompletely understood. Prior studies have shown that 'compulsive-like' behaviors in rodents, for example, persistent responding for ethanol (EtOH) despite punishment, are increased after chronic exposure to EtOH. The main goal of the current study was to assess the effects of chronic intermittent EtOH (CIE) exposure on multiple, putative measures of compulsive-like EtOH seeking in C57BL/6 J mice. Mice were exposed to two or four weekly cycles of CIE and then, post-withdrawal, tested for progressive ratio responding for EtOH, sustained responding during signaled EtOH unavailability and (footshock) punished suppression of responding for EtOH. Results showed that mice exposed to CIE exhibited attenuated suppression of EtOH seeking during punishment, as compared with air-exposed controls. By contrast, CIE exposure affected neither punished food reward-seeking behavior, nor other putative measures of compulsive-like EtOH seeking. Ex vivo reverse transcription polymerase chain reaction analysis of brain tissue found reduced sensitivity to punished EtOH seeking after CIE exposure was accompanied by a significant increase in gene expression of the GluN1 and GluN2A subunits of the N-methyl-d-aspartate receptor, specifically in the medial orbitofrontal cortex. Moreover, slice electrophysiological analysis revealed increased N-methyl-d-aspartate receptor-mediated currents in the orbitofrontal cortex after CIE exposure in test-naïve mice. Collectively, the current findings add to the growing body of evidence demonstrating that chronic exposure to EtOH fosters resistance to punished EtOH seeking in association with adaptations in cortical glutamatergic transmission.

Extended Amygdala to Ventral Tegmental Area Corticotropin-Releasing Factor Circuit Controls Binge Ethanol Intake.

BACKGROUND: Corticotropin-releasing factor (CRF) signaling at the CRF1 receptor (CRF1R) in the ventral tegmental area (VTA) can modulate ethanol consumption in rodents. However, the effects of binge-like ethanol drinking on this system have not been thoroughly characterized, and little is known about the role of CRF2R or the CRF neurocircuitry involved. METHODS: The effects of binge-like ethanol consumption on the VTA CRF system were assessed following drinking-in-the-dark procedures. Intra-VTA infusions of selective CRF1R and/or CRF2R compounds were employed to assess the contributions of these receptors in modulating binge-like ethanol consumption (n = 89). To determine the potential role of CRF projections from the bed nucleus of the stria terminalis (BNST) to the VTA, CRF neurons in this circuit were chemogenetically inhibited (n = 32). Binge-induced changes in VTA CRF system protein and messenger RNA were also assessed (n = 58). RESULTS: Intra-VTA antagonism of CRF1R and activation of CRF2R resulted in decreased ethanol intake, which was eliminated by simultaneous blockade of both receptors. Chemogenetic inhibition of local CRF neurons in the VTA did not alter binge-like ethanol drinking, but inhibition of VTA-projecting CRF neurons from the BNST significantly reduced intake. CONCLUSIONS: We provide novel evidence that 1) blunted binge-like ethanol consumption stemming from CRF1R blockade requires intact CRF2R signaling, and CRF2R activation reduces binge-like drinking; 2) inhibiting VTA-projecting BNST CRF neurons attenuates binge-like drinking; and 3) binge-like ethanol drinking alters protein and messenger RNA associated with the VTA-CRF system. These data suggest that ethanol-induced activation of BNST-to-VTA CRF projections is critical in driving binge-like ethanol intake.

Potent and Selective Peptide-based Inhibition of the G Protein Gαq.

In contrast to G protein-coupled receptors, for which chemical and peptidic inhibitors have been extensively explored, few compounds are available that directly modulate heterotrimeric G proteins. Active Gαq binds its two major classes of effectors, the phospholipase C (PLC)-ß isozymes and Rho guanine nucleotide exchange factors (RhoGEFs) related to Trio, in a strikingly similar fashion: a continuous helix-turn-helix of the effectors engages Gαq within its canonical binding site consisting of a groove formed between switch II and helix α3. This information was exploited to synthesize peptides that bound active Gαq in vitro with affinities similar to full-length effectors and directly competed with effectors for engagement of Gαq A representative peptide was specific for active Gαq because it did not bind inactive Gαq or other classes of active Gα subunits and did not inhibit the activation of PLC-ß3 by Gß1γ2 In contrast, the peptide robustly prevented activation of PLC-ß3 or p63RhoGEF by Gαq; it also prevented G protein-coupled receptor-promoted neuronal depolarization downstream of Gαq in the mouse prefrontal cortex. Moreover, a genetically encoded form of this peptide flanked by fluorescent proteins inhibited Gαq-dependent activation of PLC-ß3 at least as effectively as a dominant-negative form of full-length PLC-ß3. These attributes suggest that related, cell-penetrating peptides should effectively inhibit active Gαq in cells and that these and genetically encoded sequences may find application as molecular probes, drug leads, and biosensors to monitor the spatiotemporal activation of Gαq in cells.

Serotonin's Complex Role in Alcoholism: Implications for Treatment and Future Research.

Current pharmacological treatments for alcohol dependence have focused on reducing alcohol consumption, but to date there are few treatments that also address the negative affective symptoms during acute and protracted alcohol withdrawal which are often exacerbated in people with comorbid anxiety and depression. Selective serotonin reuptake inhibitors (SSRIs) are sometimes prescribed to ameliorate these symptoms but can exacerbate anxiety and cravings in a select group of patients. In this critical review, we discuss recent literature describing an association between alcohol dependence, the SERT linked polymorphic region (5-HTTLPR), and pharmacological response to SSRIs. Given the heterogeneity in responsiveness to serotonergic drugs across the spectrum of alcoholic subtypes, we assess the contribution of specific 5-HT circuits to discrete endophenotypes of alcohol dependence. 5-HT circuits play a distinctive role in reward, stress, and executive function which may account for the variation in response to serotonergic drugs. New optogenetic and chemogenetic methods for dissecting 5-HT circuits in alcohol dependence may provide clues leading to more effective pharmacotherapies. Although our current understanding of the role of 5-HT systems in alcohol dependence is incomplete, there is some evidence to suggest that 5-HT3 receptor antagonists are effective in people with the L/L genotype of the 5-HTTLPR polymorphism while SSRIs may be more beneficial to people with the S/L or S/S genotype. Studies that assess the impact of serotonin transporter polymorphisms on 5-HT circuit function and the subsequent development of alcohol use disorders will be an important step forward in treating alcohol dependence.

Nociceptin receptor antagonist SB 612111 decreases high fat diet binge eating.

Binge eating is a dysregulated form of feeding behavior that occurs in multiple eating disorders including binge-eating disorder, the most common eating disorder. Feeding is a complex behavioral program supported through the function of multiple brain regions and influenced by a diverse array of receptor signaling pathways. Previous studies have shown the overexpression of the opioid neuropeptide nociceptin (orphanin FQ, N/OFQ) can induce hyperphagia, but the role of endogenous nociceptin receptor (NOP) in naturally occurring palatability-induced hyperphagia is unknown. In this study we adapted a simple, replicable form of binge eating of high fat food (HFD). We found that male and female C57BL/6J mice provided with daily one-hour access sessions to HFD eat significantly more during this period than those provided with continuous 24h access. This form of feeding is rapid and entrained. Chronic intermittent HFD binge eating produced hyperactivity and increased light zone exploration in the open field and light-dark assays respectively. Treatment with the potent and selective NOP antagonist SB 612111 resulted in a significant dose-dependent reduction in binge intake in both male and female mice, and, unlike treatment with the serotonin selective reuptake inhibitor fluoxetine, produced no change in total 24-h food intake. SB 612111 treatment also significantly decreased non-binge-like acute HFD consumption in male mice. These data are consistent with the hypothesis that high fat binge eating is modulated by NOP signaling and that the NOP system may represent a promising novel receptor to explore for the treatment of binge eating.

Mu Opioid Receptor Modulation of Dopamine Neurons in the Periaqueductal Gray/Dorsal Raphe: A Role in Regulation of Pain.

The periaqueductal gray (PAG) is a brain region involved in nociception modulation, and an important relay center for the descending nociceptive pathway through the rostral ventral lateral medulla. Given the dense expression of mu opioid receptors and the role of dopamine in pain, the recently characterized dopamine neurons in the ventral PAG (vPAG)/dorsal raphe (DR) region are a potentially critical site for the antinociceptive actions of opioids. The objectives of this study were to (1) evaluate synaptic modulation of the vPAG/DR dopamine neurons by mu opioid receptors and to (2) dissect the anatomy and neurochemistry of these neurons, in order to assess the downstream loci and functions of their activation. Using a mouse line that expresses eGFP under control of the tyrosine hydroxylase (TH) promoter, we found that mu opioid receptor activation led to a decrease in inhibitory inputs onto the vPAG/DR dopamine neurons. Furthermore, combining immunohistochemistry, optogenetics, electrophysiology, and fast-scan cyclic voltammetry in a TH-cre mouse line, we demonstrated that these neurons also express the vesicular glutamate type 2 transporter and co-release dopamine and glutamate in a major downstream projection structure-the bed nucleus of the stria terminalis. Finally, activation of TH-positive neurons in the vPAG/DR using Gq designer receptors exclusively activated by designer drugs displayed a supraspinal, but not spinal, antinociceptive effect. These results indicate that vPAG/DR dopamine neurons likely play a key role in opiate antinociception, potentially via the activation of downstream structures through dopamine and glutamate release.

Lateral Hypothalamus GABAergic Neurons Modulate Consummatory Behaviors Regardless of the Caloric Content or Biological Relevance of the Consumed Stimuli.

It was recently reported that activation of a subset of lateral hypothalamus (LH) GABAergic neurons induced both appetitive (food-seeking) and consummatory (eating) behaviors in vGat-ires-cre mice, while inhibition or deletion of GABAergic neurons blunted these behaviors. As food and caloric-dense liquid solutions were used, the data reported suggest that these LH GABAergic neurons may modulate behaviors that function to maintain homeostatic caloric balance. Here we report that chemogenetic activation of this GABAergic population in vGat-ires-cre mice increased consummatory behavior directed at any available stimulus, including those entailing calories (food, sucrose, and ethanol), those that do not (saccharin and water), and those lacking biological relevance (wood). Chemogenetic inhibition of these neurons attenuated consummatory behaviors. These data indicate that LH GABAergic neurons modulate consummatory behaviors regardless of the caloric content or biological relevance of the consumed stimuli.

Effects of chronic ethanol exposure on neuronal function in the prefrontal cortex and extended amygdala.

Chronic alcohol consumption and withdrawal leads to anxiety, escalated alcohol drinking behavior, and alcohol dependence. Alterations in the function of key structures within the cortico-limbic neural circuit have been implicated in underlying the negative behavioral consequences of chronic alcohol exposure in both humans and rodents. Here, we used chronic intermittent ethanol vapor exposure (CIE) in male C57BL/6J mice to evaluate the effects of chronic alcohol exposure and withdrawal on anxiety-like behavior and basal synaptic function and neuronal excitability in prefrontal cortical and extended amygdala brain regions. Forty-eight hours after four cycles of CIE, mice were either assayed in the marble burying test (MBT) or their brains were harvested and whole-cell electrophysiological recordings were performed in the prelimbic and infralimbic medial prefrontal cortex (PLC and ILC), the lateral and medial central nucleus of the amygdala (lCeA and mCeA), and the dorsal and ventral bed nucleus of the stria terminalis (dBNST and vBNST). Ethanol-exposed mice displayed increased anxiety in the MBT compared to air-exposed controls, and alterations in neuronal function were observed in all brain structures examined, including several distinct differences between subregions within each structure. Chronic ethanol exposure induced hyperexcitability of the ILC, as well as a shift toward excitation in synaptic drive and hyperexcitability of vBNST neurons; in contrast, there was a net inhibition of the CeA. This study reveals extensive effects of chronic ethanol exposure on the basal function of cortico-limbic brain regions, suggests that there may be complex interactions between these regions in the regulation of ethanol-dependent alterations in anxiety state, and highlights the need for future examination of projection-specific effects of ethanol in cortico-limbic circuitry.

NPY signaling inhibits extended amygdala CRF neurons to suppress binge alcohol drinking.

Binge alcohol drinking is a tremendous public health problem because it leads to the development of numerous pathologies, including alcohol abuse and anxiety. It is thought to do so by hijacking brain systems that regulate stress and reward, including neuropeptide Y (NPY) and corticotropin-releasing factor (CRF). The central actions of NPY and CRF have opposing functions in the regulation of emotional and reward-seeking behaviors; thus, dysfunctional interactions between these peptidergic systems could be involved in the development of these pathologies. We used converging physiological, pharmacological and chemogenetic approaches to identify a precise neural mechanism in the bed nucleus of the stria terminalis (BNST), a limbic brain region involved in pathological reward and anxiety behaviors, underlying the interactions between NPY and CRF in the regulation of binge alcohol drinking in both mice and monkeys. We found that NPY Y1 receptor (Y1R) activation in the BNST suppressed binge alcohol drinking by enhancing inhibitory synaptic transmission specifically in CRF neurons via a previously unknown Gi-mediated, PKA-dependent postsynaptic mechanism. Furthermore, chronic alcohol drinking led to persistent alterations in Y1R function in the BNST of both mice and monkeys, highlighting the enduring, conserved nature of this effect across mammalian species. Together, these data provide both a cellular locus and signaling framework for the development of new therapeutics for treatment of neuropsychiatric diseases, including alcohol use disorders.

Functional alterations in the dorsal raphe nucleus following acute and chronic ethanol exposure.

Alcoholism is a pervasive disorder perpetuated in part to relieve negative mood states like anxiety experienced during alcohol withdrawal. Emerging evidence demonstrates a role for the serotonin-rich dorsal raphe (DR) in anxiety following ethanol withdrawal. The current study examined the effects of chronic ethanol vapor exposure on the DR using slice electrophysiology in male DBA2/J mice. We found that chronic ethanol exposure resulted in deficits in social approach indicative of increased anxiety-like behavior at both 24 h and 7 days post-ethanol exposure. At 24 h post-ethanol exposure, we observed increased excitability and decreased spontaneous inhibitory transmission (inhibitory postsynaptic currents, IPSCs) in the DR. At 7 days post-ethanol exposure, we observed increased spontaneous and miniature excitatory transmission (excitatory postsynaptic currents, EPSCs). Because acute ethanol alters GABA transmission in other brain regions, we assessed the effects of ex vivo ethanol (50 mM) on miniature IPSCs (mIPSCs) in the DR 24-h post-ethanol exposure. Bath application of ethanol enhanced the amplitude of mIPSCs in cells from ethanol-naive and chronic intermittent ethanol-exposed (CIE) mice, but significantly enhanced the frequency of mIPSCs only in cells from CIE mice, suggesting that DR neurons are more sensitive to the inhibitory effects of acute ethanol following CIE. On the basis of these findings, we hypothesize that net excitation of DR neurons following chronic ethanol exposure contributes to enhanced anxiety during ethanol withdrawal, and that increased sensitivity of DR neurons to subsequent ethanol exposure may mediate acute ethanol's ability to relieve anxiety during ethanol withdrawal.