Dopamine and Benzodiazepine-Dependent Mechanisms Regulate the EtOH-Enhanced Locomotor Stimulation in the GABAA α1 Subunit Null Mutant Mice

Abstract

The present study investigated the role of the alpha1-containing GABA(A) receptors in the neurobehavioral actions of alcohol. In Experiment 1, mice lacking the alpha1 subunit (alpha1 (-/-)) were tested for their capacity to initiate operant-lever press responding for alcohol or sucrose. Alcohol intake in the home cage was also measured. In Experiment 2, the alpha1 (-/-) mice were injected with a range of alcohol doses (0.875-4.0 g/kg; i.p.) to evaluate the significance of the alpha1 subunit in alcohol's stimulant actions. In Experiment 3, we determined if the alcohol-induced stimulant effects were regulated via dopaminergic (DA) or benzodiazepine (BDZ)-dependent mechanisms. To accomplish this, we investigated the capacity of DA (eticlopride, SCH 23390) and BDZ (flumazenil, betaCCt) receptor antagonists to attenuate the alcohol-induced stimulant actions. Compared with wild-type mice (alpha1 (+/+)), the null mutants showed marked reductions in both EtOH and sucrose-maintained responding, and home-cage alcohol drinking. The null mutants also showed significant increases in locomotor behaviors after injections of low-moderate alcohol doses (1.75-3.0 g/kg). betaCCt, flumazenil, eticlopride, and SCH 23390 were able to attenuate the alcohol-induced stimulation in mutant mice, in the absence of intrinsic effects. These data suggest the alpha1 receptor plays an important role in alcohol-motivated behaviors; however, it also appears crucial in regulating the reinforcing properties associated with normal ingestive behaviors. Deleting the alpha1 subunit of the GABA(A) receptor appears to unmask alcohol's stimulatory effects; these effects appear to be regulated via an interaction of both DA- and GABA(A) BDZ-dependent mechanisms.