Effects of β-(Tyr⁹)melantropin-(9-18) decapeptide on passive and active avoidance behavior and on open-field activity of rats

The effects of the administration of β-(Tyr⁹)melanotropin-(9-18) into the lateral ventricle in a dose of 1.0 μg in 2 μl were studied on passive avoidance behavior, extinction of active avoidance behavior, and open-field activity in rats. β-(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 β-(Tyr⁹)melanotropin-(9-18) has distinct neurotropic properties, and is able to modify behavioral reactions.