Stimulus significance and chlorpromazine effects on the expression of avoidance learning in mice

Abstract

Mice trained in a one-trial passive avoidance learning situation were treated with chlorpromazine (2 mg/kg i.p.) 10 min before being tested 24 hr after training. The reduced expression of learned avoidance and the accelerated extinction noted under the influence of the drug were found to be offset if the experimental subjects had received prior training in a T-maze in which the discriminanda were the same as those used in the avoidance learning situation. These findings are related to a possible mechanism of action of the drug involving the reduction of apparent stimulus significance. The likely physiological basis of such a mechanism is briefly discussed.