Conditioned drug effects of pimozide, haloperidol and chlorpromazine on methamphetamine-induced behavior.

The separate effects of pimozide, haloperidol and chlorpromazine on conditioned behavioral responses and whether there is a difference when the drug is administered accompanied by a sound stimulus were examined in rats. The results showed a similar degree of inhibition could be obtained by saline plus sound as that by pimozide alone. The pimozide with sound group showed a higher inhibition rate than that of the other two groups of rats. In the haloperidol with sound group, a stronger inhibition appeared and furthermore when the injection was discontinued, conditioned abnormal behavior that had been inhibited began to recover. The chlorpromazine group was similar to the haloperidol group. This means that repeated saline injections accompanied by sound and each drug individually inhibits conditioned abnormal behavior and that each drug combined with sound causes the strongest inhibition. The findings obtained suggested that the antipsychotics examined could have conditioned drug effects.