Discriminative stimulus properties of cocaine and d-amphetamine,and antagonism by haloperidol: A comparative study

This paper presents a comparative study of the discriminative stimulus properties of cocaine and d-amphetamine in the rat. Using a discrete-trial, food-reward, two-lever drug discrimination procedure, one group of rats (n = 7) were trained to discriminate 10 mg/kg cocaine from saline, whereas 1.25 mg/kg d-amphetamine served as a cue to a second group (n = 6). Following training, stimulus generalization gradients were determined for cocaine and d-amphetamine in both groups, and so were the antagonistic effects of haloperidol vs the training drug conditions. The results indicate that the acquisition of discrimination proceeded at a comparable rate in the two groups. In both groups, d-amphetamine was about 5 times more potent than cocaine, and individual threshold doses for the two drugs showed a significant correlation. Haloperidol appeared equally effective in antagonizing 1.25 mg/kg d-amphetamine and 10 mg/kg cocaine. These findings converge to suggest that to a large extent the cueing properties of d-amphetamine and cocaine are similar.