Central Amygdala Kappa Opioid Receptor Mechanisms Underlying Effects of Ethanol

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DESCRIPTION (provided by applicant): The kappa opioid receptor (KOR) and its endogenous agonist, dynorphin, have been identified as critical for alcohol abuse and dependence. Human genetic studies have shown that the KOR system is associated with alcohol dependence (Xuei et al., 2006). In addition, behavioral studies using animals reported that KOR agonists decrease voluntary ethanol intake (Lindholm et al., 2001), while KOR antagonists decrease ethanol intake in chronically ethanol-treated animals (Walker and Koob, 2008). The KOR system has been suggested to mediate dysphoric effects of drugs of abuse including ethanol, and it has recently suggested that KOR system plays a role downstream of the corticotrophin releasing factor (CRF) system (Land et al., 2008). This proposal will test the hypothesis that the KOR system in the central amygdala nucleus (CeA), a critical brain region involved in stress and anxiety behavior as well as drug addiction, mediates acute ethanol effects and that the KOR system in CeA is dysregulated following chronic ethanol treatment. A second hypothesis to be tested is that KORs mediate ethanol effects through the CRF system in CeA. This study will examine the KOR system and its interaction with the CRF system using whole cell patch clamp electrophysiological techniques. We will investigate the role of these systems in mediating ethanol effects in the CeA in rodent brain slices taken from naove and chronically ethanol-treated animals. We will examine tonic effects of the KOR system as well as effects of acute activation of the KOR system on spontaneous excitatory and inhibitory neurotransmission in the CeA network. Studies will be performed in two subregions of central amygdala, lateral and medial divisions, as these divisions exhibit differential distribution of dynorphin (the putative endogenous KOR ligand) (Marchant et al., 2007). We will examine the effect of KOR antagonism and activation in four different conditions including (1) control conditions, (2) acute in vitro pretreatment with CRF, (3) acute in vitro pretreatment with ethanol, and (4) in brain slices from chronic ethanol treated animals and pair-fed animals with an equicaloric control diet. To investigate whether the KOR effect is dependent on CRF receptor activation, we will repeat experiments in the presence of CRF receptor antagonists. Understanding the role of the kappa opioid system in mediating alcohol actions in CeA should facilitate development of therapeutic alternatives to ameliorate alcohol dependence and abuse. PUBLIC HEALTH RELEVANCE: Alcohol dependence is a chronic disease characterized by uncontrollable excessive consumption of alcohol. Currently available pharmacological interventions have limited beneficial effects. This project will be investigating a candidate mechanism underlying alcohol dependence, a kappa opioid system in the amygdala. The outcome of this project will contribute to develop more effective pharmacological therapeutics to ameliorate and/or treat alcohol dependence.