The overall goal of this proposal is to identify and systematically examine benzodiazepine (BDZ) receptor ligands which attenuate the reinforcing properties of ethanol (ETOH). To accomplish this goal, the high alcohol drinking (HAD) rat and measures of ETOH reinforcement will be used. Quantitative receptor autoradiography (QAR) will also be used to determine if the binding affinity of effective BDZ ligands at central nervous system (CNS) sites correlates with the magnitude of behavioral effects. The main hypothesis to be tested is whether certain BDZ inverse agonist and antagonist ligands can selectively attenuate measures of ETOH reinforcement; this may be related to their binding at diazepam sensitive (DS), and to a lesser degree at diazepam insensitive (DI) conformations of GABAA-BDZ receptors. Initial dose-effect and time course studies will examine the ability of agents to attenuate ETOH intake using operant methodology. It is hypothesized that agents with high affinity for DS sites will be effective ETOH antagonists; however, agents with high affinity at both DS and DI sites should produce more potent and prolonged antagonism. In a second series of experiments, the threshold for electrical brain stimulation reward (BSR) will be compared in naive HAD and low alcohol drinking (LAD) rats. The role of oral (contingent) ETOH administration will also be tested for comparison with intra gastric (IG) (noncontingent) infusions in HAD rats. In addition, HAD and LAD rats will be compared for sensitivity to BSR following noncontingent ETOH administration. It is hypothesized that HAD rats will evidence a lower threshold and higher rate of responding for BSR compared with LAD rats under naive and following noncontingent ETOH. Contingent ETOH administration is expected to yield a more positive (euphoric) action on BSR compared with the noncontingent route in HAD rats. Studies of effective anti-ETOH agents using the optimal ETOH BSR threshold route will then be conducted in HAD rats. Using QAR, a third series of experiments will examine both inhibition and time course profiles of agents found effective as ETOH antagonists at CNS sites. It is hypothesized that highly effective ETOH antagonists should evidence greater binding at DS and DI sites hypothesized to mediate ETOH reinforcement, and that interactions at these sites may mediate in part (indirectly influence) activation of underlying neuroanatomical substrates contributing to the reinforcing properties of ETOH. It is further hypothesized that the behavioral and binding time course profiles will not be parallel. These studies should advance our understanding of the role the GABAA-BDZ receptor complex plays in mediating ETOH reinforcement, and may lead to the development of treatments for alcohol abuse and alcoholism.
