The role of pro-opiomelanocortin neuronal circuitry in mediating ethanol consumption

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Project Abstract Alcohol abuse is a worldwide public health concern and leads to an estimated 90,000 alcohol-related deaths in the United States annually. Recent evidence suggests that ethanol may promote its euphoric and motivational effects, in part, by activating the endogenous opioid system. Further supporting the role of the endogenous opioid system in alcohol abuse, one of the most frequently utilized medications for treating alcohol use disorders to date is naltrexone, a broad spectrum opioid receptor antagonist. One particular circuit of the endogenous opioid system consists of pro-opiomelanocortin (POMC) producing neurons in the arcuate nucleus (ArcN) of the hypothalamus, which project heavily to reward-related areas such as the ventral tegmental area (VTA), nucleus accumbens (NAc) and amygdala (Amy). These neurons utilize POMC-derived neuroactive peptides, such as β- endorphin (B-END), in conjunction with amino acid transmitters to regulate their local and extrahypothalamic targets. Based on this utilization of neuroactive peptides as well as excitatory and inhibitory co-transmitters, it is likely that POMC neurons can differentially regulate their local and extrahypothalamic targets. Ethanol administration induces B-END release in the NAc, which is thought to underlie the reinforcing properties and motivational behaviors of alcohol. The overarching goal of this proposal is to test the hypothesis that POMC- expressing neurons of the hypothalamus are directly involved in regulating ethanol consumption. These results will broaden the scope of our current understanding of the neural basis of ethanol intake and its potential relevance to alcohol abuse. Thus, I propose to examine the role of POMC circuitry originating in the ArcN of the hypothalamus in modulating ethanol consumption via bidirectional chemogenetic manipulation. Specifically, I hypothesize that activation of local POMC circuitry within the ArcN will promote ethanol consumption and that activation of POMC-expressing neurons will lead to increased levels of β-endorphin within the hypothalamus and its reward-related target regions (the NAc, VTA and Amy). Additionally, I aim to determine circuit-specific activation of POMC neuronal projections following ethanol consumption, where I predict that ethanol will have preferential activation of POMC-expressing neurons projecting to the NAc and VTA. Ultimately, these studies will advance the current understanding of ethanol-mediated effects on the endogenous opioid system and may lead to novel approaches to better treat alcohol abuse. Through these proposed studies, I will be trained in in vivo chemogenetics, animal behavioral testing, anatomical tracing, immunohistochemistry, western blot analysis and confocal microscopy.