Dependence Driven Alterations in Ethanol Reinforcement

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This project is a component of an INIA Consortium focussed on identifying the molecular, cellular, and behavioral neuroadaptations in specific brain neurocircuitry that result in excessive ethanol intake. Our overarching hypothesis is that genetic differences and/or neuroadaptations in circuitry of the extended amygdala are responsible for individual differences in vulnerability to excessive consumption of alcohol. This component will address the first Specific Aim of the INIA Consortium, i.e., these studies are intended to establish animal models to identify specific brain sites involved in excessive consumption of alcohol. We propose to use a two-phase protocol involving passive exposure to ethanol via a chronic intragastric (IG) cannula followed by a self-infusion test procedure in which voluntary ingestion of a flavored solution is paired with IG ethanol. The general purpose of our first Specific Aim is to establish and optimize an animal model of excessive ethanol intake driven by dependence/withdrawal in genetically heterogeneous rats and mice. Parallel studies in each species will focus on variables related to the initial schedule of chronic ethanol exposure and access during self-infusion testing. Specific Aim 2 will address the hypothesis of genetic differences in sensitivity to dependence-driven ethanol reinforcement. We will use the behavioral model established in Specific Aim 1 to characterize various genetic animal models selected on the basis of known differences in ethanol drinking preference or sensitivity to ethanol withdrawal. We will also test at least two new genetic models developed at other INIA sites. Finally, to characterize the neural circuitry underlying excessive ethanol intake produced by this model, Specific Aim 3 will examine effects of microinfusion of selective agonists/antagonists directly into specific parts of the extended amygdala. The goal is to identify discrete brain areas and transmitter systems that influence the magnitude and persistence of excessive ethanol intake. These studies will use rats and will focus primarily on GABA-A and dopamine system influences in the central nucleus of the amygdala (CeA) and ventral tegmental area (VTA). The long-term goal of this project is to understand the neurobiology of the excessive drinking that contributes to alcoholism in humans.