Involvement and neuroplasticity of cholinergic interneurons of the nucleus accumbens in initiation and excessive alcohol drinking
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Alcoholism is a complex disease that exists as a specific set of behaviors, such as the preoccupation with obtaining alcohol and compulsive alcohol drinking. Currently, more than 18 million adults in the United States suffer from alcohol abuse or alcoholism. This disease poses serious medical and economic consequences for society. Identifying the neurobiological mechanisms that underlie alcohol drinking, specifically the transition from initiation to binge drinking is critical for improved treatments for alcoholics and the vulnerability for relapse in those recovering. Many studies have identified brain regions and molecular mechanisms that underlie various stages of alcohol abuse; however few have investigated the role of specific cell types within these areas. The overarching hypothesis of the studies in this dissertation is that cholinergic interneurons of the nucleus accumbens (NAc) are key neural substrates that underlie alcohol drinking, and as drinking continues; neuroadaptations within these cells then facilitate such behaviors as compulsive alcohol drinking. More specifically, these studies tested whether 1) cholinergic cell ablation in the NAc causes a decrease in alcohol drinking in C57BL/6J mice, 2) neuroadaptive changes in dopamine (DA) D2 receptor and cyclin dependent kinase 5 (Cdk5) occur within these cells following initiation alcohol drinking, and to a greater extent following binge alcohol drinking in C57BL/6J mice, and 3) neuroadaptive changes in DA D2 receptor and Cdk5 also occur in brain regions that have been implicated in the rewarding and reinforcing effects of alcohol in inbred alcohol-preferring (iP) rats. The present findings report a causal role for accumbal cholinergic neurons in binge alcohol drinking and identify DA D2 receptor and Cdk5 neuroadaptations following initiation and binge alcohol drinking. These studies identify the involvement of cholinergic interneurons in binge drinking and reveal alcohol-induced region- and cell-specific receptor and molecular changes that occur with continued drinking. These findings contribute to the understanding of the neurobiological mechanisms that underlie alcohol drinking, and provide the basis for cholinergic targeted treatments designed to attenuate binge drinking. These data also provide the groundwork for future studies aimed to examine receptor and intracellular molecular changes that occur with compulsive alcohol drinking, craving, and relapse.