The ethanol stimulus in rats with differing ethanol preferences

Alcohol-accepting (AA) and alcohol-nonaccepting (ANA) rats (Alko, Finland) were tested for their ability to master a shock-motivated (0.6 mA scrambled AC current) T-maze discrimination in which IP injections of ethanol (1.0 g/kg, 10% w/v in saline, 20-min latency) and, on alternate days, equivolume saline were employed as a discriminative stimuli signalling the safety of right or left goal compartments. ANA rats reached the criterion level of performance (eight of ten correct first-trial responses) more quickly than did AA rats (12.3±2.3 versus 31.4±7.7 sessions, P<0.01) and also maintained a superior level of performance throughout the course of the experiment, suggesting that ethanol may have been a more salient cue for ANA rats than for AA rats. Injections of acetaldehyde (0.1–0.25 g/kg, 1.0–2.5% w/v in saline) produced ethanol-appropriate responding to a greater extent in ANA rats than in AA rats, indicating that the actions of acetaldehyde may contribute importantly to the stimulus condition produced by the injection of ethanol in ANA rats. Sodium pentobarbital (10.0 g/kg) was equally effective in mimicking the action of ethanol in both AA and ANA rats. AA and ANA rats did not differ significantly in the impairment of motor performance produced by a range of ethanol doses, suggesting that differences in stimuli related to motor impairment do not contribute to the differences observed in the cue value of ethanol for AA and ANA rats.