Comparison of alcohol-preferring (P) and nonpreferring (NP) rats on tests of anxiety and for the anxiolytic effects of ethanol.

Rats of the selectively bred alcohol-preferring P and alcohol-nonpreferring NP lines were evaluated using three different behavioral measures of anxiety. Compared with NP rats, P rats (1) showed greater footshock-induced suppression of operant responding in an approach-avoidance conflict test; (2) spent less time in the open arms of an elevated plus maze; and (3) took longer in a passive avoidance test to step down from a platform to a grid floor where footshock was received 24 hours earlier. These findings indicate a greater degree of anxiety in the P than in the NP line of rats in these situations. Pretreatment with intraperitoneal (IP) ethanol (0.5-1.0 g/kg) injections produced anticonflict or anxiolytic effects in P but not in NP rats. However, the anticonflict effects of ethanol were small relative to those produced by chlordiazepoxide (CDP, 7.5 mg/kg) in both lines. The results demonstrate that selective breeding for divergent oral ethanol preference has produced associated differences between the P and NP lines of rats in behavioral tests of anxiety and in the anxiolytic effects of ethanol.