GABA RECEPTOR MECHANISMS IN ALCOHOL REINFORCEMENT

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There is increasing evidence that GABAA-benzodiazepine (BDZ) receptors are involved in the regulation of EtOH-self- administration. The goal of this proposal is to identify specific neurobiological substrates of GABAA-BDZ neurotransmission which mediate EtOH reinforcement. To accomplish this goal, the selectively bred high alcohol drinking (HAD) 1 and 2 rat lines will be used. The main hypothesis to be tested is that GABAA-BDZ neuroanatomical circuits in two extended amygdala loci [e.g., central nucleus of the amygdala, bed nucleus of the stria terminalis], mediate in part, activation of underlying neuroanatomical substrates contributing to the reinforcing properties of EtOH. First, dose-effect and time course studies will examine the capacity of site-specific microinjections of high affinity BDZ inverse agonists, a BDZ antagonist and the GABAA antagonist SR 95531 in the central nucleus of the amygdala and bed nucleus of the stria terminalis to attenuate EtOH intake using scheduled controlled responding (i.e., operant methodology). It is hypothesized that inverse agonists and antagonists with similar binding affinity should be equally effective as EtOH antagonists. Effective antagonists (i.e., inverse agonists) of EtOH-maintained responding should be antagonized by competitive BDZ antagonist, since their suppression should be mediated by a direct action at the BDZ component of the GABAA complex. Second, to systematically evaluate the selectivity of the agents to suppress EtOH-motivated responding, a 4-stage behavioral analysis will be employed. It is hypothesized that agents (e.g., inverse agonists, BDZ antagonist, SR 95531) which specifically affect the reinforcing aspects of EtOH should not alter responding of alternative reinforcers with similar reinforcing efficacy (i.e., saccharin), or similar post-ingestional caloric properties (i.e., sucrose). Finally, it is hypothesized that interactions at GABAA-BDZ sites may modulate the function of monoaminergic neurons sustaining EtOH-seeking behaviors. These studies should contribute to a scientific understanding of the role of GABAA-BDZ receptor complex plays in regulating EtOH seeking behavior.