Effects of low and moderate doses of chlorpromazine on discrimination learning in the rat

The effects of chlorpromazine on the acquisition of a brightness discrimination with food reward were examined. Doses of 0.5, 1.0 or 2.0 mg/kg of CPZ as well as saline were administered intraperitoneally to 4 groups of 7 Sprague-Dawley rats, 1 h prior to testing. After a 3-week period of habituation and pre-training, rats were tested 20 trials a day, 7 days a week. No drug effect was found on the number of trials to reach a criterion of 18/20 successive correct responses, which required an average of 6.2 days of training. Precriterion latencies, however, showed an increase as a function of increasing dose level. Post-choice latencies were not affected, eliminating motor retardation as an explanation for the latency effect.