[Selective effect of morphine and diazepam on aggressiveness caused by prolonged administration of apomorphine to rats].

In experiments on rats administration of apomorphine (0.5 mg/kg twice a day for 14 days) caused the intensification of aggressiveness. This exerted no substantial effect on stereotyped behavior. Haloperidol produced inhibitory effect both on aggressiveness and stereotypy. The GABA derivative phenybut did not change the effects of apomorphine. Administration of morphine and diazepam produced a selective inhibition of aggressiveness. In doses exerting antiaggressive effect these substances produced no substantial effect on stereotypy. This antiaggressive effect of morphine and diazepam was suppressed by nalorphine. It is suggested that the endogenous opiate system of the CNS participates in the development of the apomorphine-induced aggressiveness.