The effects of the GABA(B) agonist baclofen on the temporal and structuralcharacteristics of ethanol intake

The present study examined the behavioral processes mediating the influence of the GABAB agonist baclofen on the maintenance of voluntary ethanol inta ke. Long-Evans rats were randomly assigned to two groups, one receiving bac lofen (10 mg/kg, IF) and the other an equal Volume of saline. Subjects were presented with a free choice of ethanol (10% v/v) and water immediately fo llowing drug injections, which occurred every other day. The results demons trated that baclofen treatment resulted in an overall increase in the-intak e of absolute ethanol but failed to influence the intake of water. In contr ast, food intake was substantially attenuated as evidenced by a decrease in the number of pellets consumed in subjects treated with baclofen. A microa nalysis of the patterns of food and fluid bouts indicated that the enhanced ethanol intake was primarily a function of an increase in the frequency of ethanol bouts. In contrast, the decrease in food intake appeared to be a r eflection of a decrease in the size of the food meals but not their frequen cy. An analysis of the temporal pattern of intake over the 23-h test sessio ns indicated that baclofen treatment produced a biphasic effect on ethanol intake with a slight decrease in intake during the first hour following tre atment. Baclofen-treated animals then were observed to consume greater amou nts of ethanol than did saline controls throughout the remainder of the dar k cycle as well as into the light cycle. Although ethanol intake gradually decreased in controls throughout the light cycle, baclofen-treated subjects maintained a consistent level of intake throughout this period. Furthermor e, there was a clear dissociation between the temporal pattern of ethanol i ntake and that of food and water, as intake of the latter substances was sh own to decrease during the first hour following injection, but unlike with ethanol, no increase in intake was observed during the remainder of the tes t session. The nature of the effects of baclofen observed in the present st udy would suggest that the GABA, receptor system may not play a central rol e in the mediation of voluntary ethanol intake. (C) 1999 Elsevier Science I nc. All rights reserved.