[Discrimination reversal learning in rats under the treatment of chlordiazepoxide: effect of overtraining].

A total of 48 rats were run in a black-white discrimination (original) learning task to the learning criterion of 18/20 correct responses. Correct responses were rewarded by food and a non-correction method was used. One group was intraperitoneally injected with 15 mg/kg of chlordiazepoxide (CDP) and the other with physiological saline (SAL), 30 min prior to the beginning of the daily trials. For half of the rats (NOT) of each group, reversal learning began on the next day after reaching the criterion, and for the other half (OT), 100 additional trials(overtraining) were given before the reversal. The results showed that CDP as well as overtraining significantly retarded the reversal learning. CDP had no effect on the original learning. Further analysis of the data revealed that perseverative errors early in the reversal increased significantly under the conditions of CDP and overtraining, but trials to criterion after the first occurrence of the correct response were not affected by both CDP and overtraining. These results were discussed in terms of CDP's disinhibitory action and overtraining reversal effect in such relatively easy discrimination task as in the present experiment.