Effects of ethanol on punished and nonpunished responding under conditions of equated reinforcement rates and similar response rates.

Lever pressing by pairs of rats was maintained under random-ratio (first subject) and yoked-interval (second subject) schedules of food presentation. The inter-reinforcement intervals generated under the ratio schedule comprised the interval values for the second (yoked) subject. This arrangement yielded nearly equivalent rates of food presentation for each subject pair. For the first rat of each pair a random-ratio schedule of shock presentation was added to the ratio schedule of food presentation. This manipulation resulted in similar rates of punished (first rat) and nonpunished (second rat) responding within subject pairs. Ethanol administration (0.25-1.5 g/kg) generally resulted in dose-related decreases in both punished and nonpunished responding. In general, punishment-specific effects were not obtained. These results suggest that ethanol may not be as effective as chlordiazepoxide or pentobarbital in increasing punished responding even when the effects of baseline response and reinforcement rates are controlled.