Neurochemical Manipulation of Withdrawal-Induced Drinking

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Project Summary We have been using a combination of genetic and environmental manipulations to induce high ethanol intake in mice, defined as alcohol intake leading to a blood ethanol concentration (BEC) greater than 100 mg%. We determined that exposure to intermittent ethanol vapor and multiple withdrawal episodes (i.e., MW group) produced high ethanol consumption and withdrawal symptoms that were consistent with the development of physical dependence in these animals. This procedure has been termed "Withdrawal-Induced Drinking" (WID) and is thought to be one behavioral model of the increased alcohol consumption in dependent animals (also termed "dependence-induced" drinking). Preliminary data indicate that acamprosate (complex glutamatergic modulator), but not naltrexone (opioid receptor antagonist), significantly decreased the expression of WID. Subsequent studies determined that systemic administration of baclofen (GABAB receptor agonist), MPEP (mGluR5 antagonist), and NBI 27914 (CRF1 receptor antagonist) significantly decreased the expression of WID. Finally, intra amygdala administration of the CRF receptor antagonist D-Phe-CRF(12-41) also selectively decreased the high alcohol intake in the MW group without altering ethanol intake in the Control group. The present proposal will continue this line of inquiry with the WID model to determine the key neurotransmitters and neuropeptides that modulate the expression of WID and begin to discern neural sites that are important for the expression of WID. We hypothesize that neuroadaptations in the central nucleus of the amygdala (CeA) and lateral septum are important for the expression of WID. Aim 1 will pharmacologically manipulate the neurochemical environment of the lateral septum, whereas Aim 2 will manipulate the neurochemical environment of the CeA, to determine the neurotransmitters and neuropeptides that are important for the high alcohol intake and expression of WID in mice. Proposed studies will use a brain site- specific microinjection technique to manipulate the GABAergic, glutamatergic, and CRF peptide environment of the lateral septum and CeA. Microinjection of receptor agonists and antagonists will allow us to determine whether the MW and Control groups are differentially sensitive to these neurochemical manipulations of the CeA and lateral septum, and whether the manipulations are sufficient to modulate the expression of WID. Collectively, the proposed research will examine the neurobiological mechanisms underlying the high alcohol consumption WID phenotype. Not only will this information help in furthering our understanding of the mechanisms underlying dependence-induced drinking, but it also will aid in the development of new strategies for the treatment of alcoholism. Project Narrative The proposed research will examine the neurobiological mechanisms underlying high alcohol consumption in dependent animals. Studies will use a brain site-specific microinjection technique to determine the key neurotransmitters and neuropeptides that modulate the increased alcohol consumption in dependent animals and begin to discern neural sites that are important for this increased alcohol intake. Not only will this information help in furthering our understanding of the mechanisms underlying dependence-induced drinking, but it also will aid in the development of new strategies for the treatment of alcoholism.