SELECTIVE ANTAGONISM OF THE RATE‐DECREASING EFFECT OF d‐AMPHETAMINE BY CHLORPROMAZINE IN A REPEATED‐ACQUISITION TASK

Pigeons acquired a different four‐response chain each session by responding sequentially on three keys in the presence of four colors. The response chain was maintained by food presentation under a fixed‐ratio schedule. When d ‐amphetamine was administered alone, the overall response rate decreased and the percent errors increased with increasing doses. When a small dose of chlorpromazine, which was ineffective when given alone, was administered in combination with d ‐amphetamine, the rate‐decreasing effect was antagonized. The antagonism was selective, however, in that the error‐increasing effect of d ‐amprotamine was augmented by chlorpromazine. The nature of the joint effect of the two drugs thus depended on the behavioral measure: rate vs. accuracy.