Amygdala NPY, anxiety phenotypes and alcohol consumption

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DESCRIPTION (provided by applicant): This proposal explores differences in temperament (anxiety) and gene expression (NPY) patterns in the amygdala as examples of endophenotypes that may contribute to ethanol consumption. Alcohol abuse and dependence is a complex disorder resulting from gene-environment interactions, but the genes encoding neuropeptide Y (NPY) or its receptor appear to confer risk for alcohol dependence in clinical and preclinical studies. This proposal expands our earlier studies and will explore the causative relationship between gene expression of NPY in the amygdala, an anxious behavioral phenotype, and ethanol consumption using the inherent phenotypic variation in anxiety seen in a rat model. The amygdala plays a critical role in anxiety-related behaviors and the anxiolytic effects of NPY may be mediated through the amygdala. Our previous studies have shown that rats with an anxious or nonanxious phenotype, defined using exploration of the elevated plus maze, display differences in ethanol preference. Changing NPY expression in amygdala also shifts ethanol preference, but only in anxious rats. Given the evidence that amygdala NPY levels regulate anxiety-related responses, the present application examines the hypothesis that NPY gene expression levels in the amygdala determine the anxiety phenotype of an individual, and low NPY levels may predispose animals for greater ethanol consumption based on this anxious phenotype. Aim 1 examines if altered NPY expression in amygdala changes anxiety state and subsequently modifies ethanol consumption in a two bottle self-administration procedure. This aim will develop lentivirus-mediated gene transfer methodologies to more directly test if lowering NPY expression in the amygdala enhances anxiety and thereby promotes ethanol consumption and/or if enhanced amygdala NPY gene expression is anxiolytic and thereby reduces ethanol preference. This Aim also characterizes anxiety phenotypes using additional behavioral models. Aim 2 will examine ethanol consumption in anxious and non-anxious phenotypes using a limited access model. This limited access method will allow more efficient screening of gene targets for development of therapeutic strategies to combat alcohol dependence. Aim 3 will examine if the pattern of neuronal activation in the amygdala (and other regions) differs with elevated plus maze exposure in the anxious and non-anxious phenotypes, and if NPY neurons are activated by ethanol injection or ethanol consumption during a limited access period. Combined with viral vector methods characterized in this developmental R21 grant these studies will lead to better characterization of specific aspects of the anxiety phenotypes regulated by NPY gene expression in the amygdala, and a better understanding of how these differences in anxiety phenotype and NPY gene expression predict ethanol consumption. Public Health Relevance: Although stress and anxiety contribute to alcohol consumption and abuse, the brain systems that predispose certain individuals to abuse alcohol and how alcohol relieves anxiety states remains unknown. The present studies use animal models to elucidate how the genes expressed in the brain region underlying emotional behaviors, namely the amygdala, control individual responses in an anxiety-provoking situation and if these same processes contribute to the alcohol consumption. The studies will provide a better understanding of how individual differences in gene expression underlie the interaction between stress and alcohol abuse, and may lead to novel targets to combat the growing problem of alcohol consumption in adolescents and adult populations.