Behavioral effects of deprenyl in aged rats.

The effects of an inhibitor of MAO-B, deprenyl, have been studied in aged male rats. Subcutaneous (s.c.) injection of deprenyl was followed by a facilitated acquisition of active avoidance behavior and a facilitated retention of passive avoidance response in a dose-dependent manner. Ambulation and rearing of aged rats in an open field were increased by deprenyl. No effect was found on grooming behavior. Apomorphine-induced stereotypies were potentiated and haloperidol-induced catalepsy was inhibited by deprenyl. Some elements of sexual behavior, i.e. latency to mounting and intromission and frequency of mounts and intromissions, were improved by deprenyl. Furthermore, deprenyl reduced the immobility of aged rats in a "despair" test, suggesting an antidepressant activity. Deprenyl seems to be effective in correcting some of the behavioral deficits of aged animals. Its behavioral effects can be related to the inhibition of cerebral MAO-B.