Effects of beta-(Tyr9)melanotropin-(9-18) decapeptide on passive and active avoidance behavior and on open-field activity of rats.

The effects of the administration of beta-(Tyr9)melanotropin-(9-18) into the lateral ventricle in a dose of 1.0 micrograms in 2 microliters were studied on passive avoidance behavior, extinction of active avoidance behavior, and open-field activity in rats. beta-(Tyr9) melanotropin-(9-18) given 30 min pretrial facilitated the acquisition of passive avoidance behavior; however, it was ineffective on retention when the material was given immediately posttrial or 30 min before retention testing. The extinction of active behavior was delayed. In open-field activity, the ambulation rate and rearing activity were increased 30 min following administration. The data suggest that beta-(Tyr9)melanotropin-(9-18) has distinct neurotropic properties, and is able to modify behavioral reactions.