Alcohol-related suppression of GIRK channel activity in the basal amygdala: a link to plasticity of glutamatergic neurotransmission and withdrawal-associated behavior?

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PROJECT SUMMARY Repeated cycles of alcohol intoxication and withdrawal foster adaptations in brain regions that regulate mood, learning, and goal-directed behavior. These adaptations are thought to promote heightened anxiety, cognitive deficits, and craving – hallmarks of alcohol use disorder (AUD) that collaborate to promote compulsive drug- seeking behavior, increase relapse susceptibility, and impede the development of adaptive behaviors that could support abstinence. Although treatment options for AUD are limited, preclinical and clinical data have generated interest in the GABAB receptor (GABABR) as a potential target for therapeutic interventions aimed at diminishing craving and reducing alcohol intake. The focus of this project is on an ethanol-induced adaptation in GABABR-dependent signaling in the basal amygdala – a key substrate of anxiety as well as learning related to rewards and aversive experiences. Using two distinct ethanol exposure models that yield repeated cycles of intoxication, we found that somatodendritic GABABR-dependent signaling is suppressed in principal neurons of the mouse BA, as measured 3-4 days after the last ethanol exposure. The adaptation is not seen in principal neurons of the lateral amygdala or pyramidal neurons of the medial prefrontal/prelimbic cortex, nor is it evoked by repeated cocaine. The adaptation is attributable to a suppression of G protein-gated inwardly rectifying K+ (GIRK) channel activity, a known determinant of anxiety-related behavior and associative learning. The goal of this project is to understand the salient features and mechanisms, as well as neurophysiological and behavioral implications, of the ethanol-induced suppression of GIRK channel activity in BA principal neurons. The two interrelated AIMs are to: (1) Elucidate mechanisms underlying the ethanol- induced suppression of GIRK channel activity. Proposed studies will employ techniques in ex vivo electrophysiology, immunoelectron microscopy, and neuron-specific viral manipulations to test the hypothesis that the ethanol-induced suppression of GIRK channel activity in BA principal neurons is mediated by the GIRK3 subunit-dependent internalization of GIRK channels. (2) Understand the downstream neurophysiological and behavioral implications of GIRK channel plasticity. Proposed studies will probe the implications of the suppression of GIRK channel activity in BA principal neurons, testing the hypothesis that it is sufficient to provoke adaptations in glutamatergic neurotransmission in discrete BA projections. In parallel, the consequences of the adaptation to anxiety-related behavior, associative (fear) learning, and voluntary ethanol consumption will be evaluated in ethanol-naïve mice, following viral genetic suppression of GIRK channel activity in BA principal neurons. Summary: This project leverages the complementary expertise of an experienced team, and the availability of custom research tools, to investigate a previously undescribed ethanol-induced neuroadaptation involving a known influence on anxiety-related behavior and associative learning. Successful completion of this project may yield new targets for interventions designed to treat AUD.