Sex differences in neuroendocrine mechanisms of HPA axis dysfunction in alcohol use disorder

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Project Summary Alcohol use disorder (AUD) is a chronic relapsing disorder with unmet pharmacological needs, characterized by compulsive alcohol seeking, excessive intake, and a negative emotional state. The hypothalamic-pituitary- adrenal (HPA) axis which normally coordinates adaptive responding to stressors, is often dysregulated in alcohol dependence. Consequently, alcoholics trying to abstain have difficulty coping with stressful events which contributes to the high rates of relapse observed in these individuals. The parvocellular neuroendocrine cells (PNCs) in the paraventricular nucleus (PVN) of the hypothalamus serve as an integrative nexus for HPA axis function, coordinating excitatory, inhibitory and endocrine signals to initiate HPA axis activation. Acute stress was shown to induce synaptic plasticity in the form of short-term potentiation (STP) at glutamatergic synapses onto the corticotropin releasing factor (CRF)-releasing PNCs. Our lab has demonstrated that rats withdrawn from chronic intermittent ethanol treatment exhibit a loss of stress-induced STP in PNCs, concomitant with blunted hormonal responses to repetitive stress. Stress hormones and neurotransmitters such as CRF and norepinephrine appear as likely candidates in gating stress-dependent HPA axis plasticity. Accordingly, I will further my training in whole-cell patch clamp electrophysiology in ex vivo microdissected PVN slices to assess the efficacy of pharmacological manipulation to normalize ethanol-induced maladaptive phenotypes. While both males and females are capable of stress-induced STP in hypothalamic CRF-releasing PNCs, potential sex-differences have not been adequately addressed. Therefore, in Specific Aim 1 I will evaluate whether chronic ethanol-induced deficits to synaptic plasticity in the PVN are sex-specific. Norepinephrine inputs are critical for the initiation and maintenance of HPA activation. Thus, in Specific Aim 2 I will evaluate the specific contributions of a1 and a2 adrenergic receptors through specific antagonists (prazosin and atipamezole, respectively) to stress and ethanol-induced changes in PNC plasticity. These aims together will test the hypothesis that sex differences in CRF and noradrenergic signaling underlies differences in ethanol induced maladaptive HPA reactivity, contributing to the gross population differences seen clinically in AUD. I have developed a rigorous and thorough training regimen to achieve these electrophysiological endpoints allowing me to develop a critical expertise in pharmacology and physiology, by which I can help bring pharmaceutical interventions to patients in need. The plan is supported by a highly capable team of mentors to facilitate my training and career development under the proposed award period.