EFFECTS OF ACUTE OR CHRONIC ADMINISTRATION OF RISPERIDONE ON MOTOR AND SEXUAL-BEHAVIOR OF MALE-RATS

A number of experiments were carried out to explore the behavioral pro file of a novel antipsychotic, risperidone, after acute or chronic adm inistration, in a dose range of 0.1-10 mg kg(-1). This drug did not af fect the acquisition and retention of avoidance behaviors in a dose of 0.1 mg kg(-1), either after acute or chronic administration. Higher d oses induced a inhibited acquisition and a facilitated extinction (onl y after chronic treatment) of active avoidance behavior, but no signif icant effect on the retention of passive avoidance responses. In contr ast, haloperidol inhibited the acquisition and facilitated the extinct ion of active avoidance behavior, and reduced the retention of passive avoidance reaction at the dose of 0.1 mg kg(-1) injected either acute ly or chronically. Ambulation and rearing of rats rated in an open fie ld was increased by risperidone injected acutely at the dose of 1 mg k g(-1). Under the same experimental conditions, grooming appeared to be reduced. In the same test, acute or chronic haloperidol 1 or 10 mg kg (-1) inhibited all behavioral items. Furthermore, in contrast to halop eridol, the acute or chronic administration of risperidone in a dose r ange of 0.1-10 mg kg(-1) did not substantially induce catalepsy and di d not affect apomorphine-induced stereotypies. Also, the dose of 0.1 m g kg(-1) induced a facilitation of male sexual behavior by increasing the frequency and reducing the latency of mountings, intromissions and ejaculations, while haloperidol 1 or 10 mg kg(-1) inhibited this beha vior. These findings suggest that the pharmacological profile of rispe ridone differs from that of classical neuroleptics, like haloperidol, probably due to different mechanism or site of action. (C) 1997 The It alian Pharmacological Society.