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 (World Health Organization, 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 and 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. GABAergic synaptic transmission was unaffected by alcohol history. 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 disk 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.SIGNIFICANCE STATEMENT Paraventricular nucleus of the hypothalamus neurons that release corticotropin releasing hormone (PVNCRH) are vital for stress response. These neurons have been understudied in relation to alcohol and withdrawal despite profound relations between stress, alcohol use disorders (AUD), and relapse. In this study, we use a variety of techniques to show that acute withdrawal from a history of alcohol impacts peripheral stress response, PVNCRH neurons, and behavior. Specifically, PVNCRH are in a hyperactive state during withdrawal, which drives an increase in active stress coping behaviors in female mice only. Understanding how alcohol use and withdrawal affects stress responding PVNCRH neurons may contribute to finding new potential targets for the treatment of alcohol use disorder.

Activation of the dorsal septum increases alcohol consumption in male C57BL/6J mice.

Binge drinking is a common pattern of excessive alcohol consumption associated with Alcohol Use Disorder (AUD) and unraveling the neurocircuitry that promotes this type of drinking is critical to the development of novel therapeutic interventions. The septal region was once a focal point of alcohol research yet has seen limited study over the last decade in relation to binge drinking. Numerous studies point to involvement of the dorsal septum (dSep) in excessive drinking and withdrawal, but few studies have manipulated this region in the context of binge drinking behavior. The present experiments were primarily designed to determine the effect of chemogenetic manipulation of the dSep on binge-like alcohol drinking in male and female C57BL/6J mice. Mice received bilateral infusion of AAVs harboring hM4Di, hM3Dq, or mCherry into the dSep and subjects were challenged with systemic administration of clozapine-N-oxide (CNO) and vehicle in the context of binge-like alcohol consumption, locomotor activity, and sucrose drinking. CNO-mediated activation (hM3Dq) of the dSep resulted in increased binge-like alcohol consumption, locomotor activity, and sucrose intake in males. DSep activation promoted sucrose drinking in female mice, but alcohol intake and locomotor activity were unaffected. Conversely, silencing (hM4Di) of the dSep modestly decreased locomotor activity in males and did not influence alcohol or sucrose intake in either sex. These data support a role for the dSep in promoting binge-like drinking behavior in a sex-dependent fashion and suggests a broad role for the region in the modulation of general appetitive behaviors and locomotor activity.

Chronic alcohol consumption alters home-cage behaviors and responses to ethologically relevant predator tasks in mice.

BACKGROUND: Alcohol withdrawal is a key component of severe alcohol use disorder. Animal models of alcohol withdrawal tend to focus on traditional anxiety/stress tests. While these have been essential to advancing our understanding of the biology of alcohol withdrawal, abrupt cessation of drinking following heavy alcohol consumption can also trigger withdrawal-related affective states that impact responses to a variety of life events and stressors. To this end, we show that behaviors in a variety of tasks that differ in task demand and intensity are altered during withdrawal in male and female mice after voluntary alcohol access. METHODS: Male and female miceunderwent six weeks of intermittent two-bottle choice alcohol exposure followed by behavioral tests. The tests included-Home cage: low-stress baseline environment to measure spontaneous natural behaviors; Open field: anxiety-inducing bright novel environment; Looming disc: arena with a protective hut where mice are exposed to a series of discs that mimic an overhead advancing predator, and Robogator-simulated predator task: forced foraging behavioral choice in the presence of an advancing robot predator that "attacks" when mice are near a food pellet in a large open arena. RESULTS: A history of alcohol exposure impacted behaviors in these tasks in a sex-dependent manner. In the home cage, alcohol induced reductions in digging and heightened stress coping through an increase in grooming time. In males, increased rearing yielded greater vigilance/exploration in a familiar environment. The open-field test revealed an anxiety phenotype in both male and female mice exposed to alcohol. Male mice showed no behavioral alterations to the looming disc task, while females exposed to alcohol showed greater escape responses than water controls, indicative of active stress-response behaviors. In males, the Robogator task revealed a hesitant/avoidant phenotype in alcohol-exposed mice under greater task demands. CONCLUSIONS: Few drugs show robust evidence of efficacy in clinical trials for alcohol withdrawal. Understanding how withdrawal alters a variety of behaviors in both males and females that are linked to stress coping can increase our understanding of alcohol misuse and aid in developing better medications for treating individuals with AUD.