ATTENUATED EFFECT OF CHLORPROMAZINE ON CONDITIONED AVOIDANCE AS A FUNCTION OF RAPID ACQUISITION

Four groups of rats were trained to avoid electric shock by responding to an initially neutral stimulus in four different test situations: 1) by turning a wheel in presence of a buzzer stimulus, 2) by turning a wheel in presence of a small light, 3) by crossing a hurdle in presence of a buzzer stimulus, and 4) by depressing a lever in presence of a tone stimulus. The facility with which the four groups acquired the conditioned avoidance response (CAR) corresponded to the order of their description above. It is postulated that what retards CAR acquisition is a competitive, conditioned crouching-freezing response. After training, all animals were tested under 1 and 2 mg/kg of chlorpromazine hydrochloride (CPZ). The degree of CAR inhibition under CPZ was a function of the acquisition history, the fastest learners being least affected. It is suggested that the additive effects of depressed arousal and disinhibition of crouching-freezing account for the differential effects of CPZ on the CAR. © 1969 Springer-Verlag.