Differential effects of GABA(A) and GABA(B) agonists on sensitization to the locomotor stimulant effects of ethanol in DBA/2 J mice

Contemporary theories of drug abuse suggest that behavioral sensitization plays an important role in addiction. However, few studies have examined the mechanisms underlying behavioral sensitization to ethanol. The present study examined the ability of THIP (2, 4, or 8 mg/kg) and baclofen (5.0, 6.25, or 7.5 mg/kg), GABA(A) and GABA(B) agonists, respectively, to prevent development of sensitization to the locomotor stimulant effects of ethanol (2 g/kg) in DBA/2 J mice. Ethanol was administered immediately before four 5-min activity trials conducted at 48-h intervals. Administration of ethanol on each of the four trials resulted in behavioral sensitization in control groups. While having few effects on activity when given alone, both GABA agonists completely blocked the acute stimulant response to ethanol on the first trial. Administration of THIP prior to ethanol on each trial failed to prevent development of sensitization. In contrast, all doses of baclofen blocked sensitization. Assessment of blood ethanol levels 15, 50 and 100 min after administration of ethanol indicated that baclofen did not change the pharmacokinetics of ethanol. These results indicate an important role for GABA(B) receptors, but not GABA(A) receptors, in development of sensitization to the locomotor stimulant effects of ethanol.