Effects of penfluridol and other drugs on apomorphine-induced stereotyped behavior in monkeys.

The effects of some drugs on apomorphine-induced stereotyped behavior were studied in male cynomolgus monkeys. Apomorphine produced the dose-dependent stereotyped behavior characterized mainly by continuous licking and biting, and repetitive movements of the hands, head and body in the monkeys. Penfluridol as well as haloperidol showed a clear antagonistic effect on the apomorphine-induced stereotyped behavior, while chlorpromazine was less antagonistic than haloperidol. The antagonistic effect of penfluridol lasted longer than that of haloperidol. Reserpine did not inhibit the apomorphine-induced stereotyped behavior though the drug elicited markedly the behavioral depression and alpha-methyl-p-tyrosine also did not block the stereotyped behavior. Nialamide did not depress the apomorphine-induced stereotyped behavior. In provoking the stereotyped behavior in monkeys, apomorphine probably acts directly on dopamine receptors in the extrapyramidal system, and penfluridol is suggested to act as a dopamine receptor blocker with a long action. The results indicate that protection against apomorphine-induced stereotyped behavior in monkeys may be a useful method for evaluating neuroleptic drugs.