Effects of beta-/Tyr9/melanotropin-/9-18/ on apomorphine-induced stereotyped cage-climbing and on striatal dopamine release in mice. Comparative studies with amphetamine.

beta-/Tyr9/melanotropin-/9-18/ significantly increased apomorphine-induced cage-climbing, while only a tendency towards an increase was observed after supersensitization with haloperidol. Amphetamine also enhanced apomorphine-induced climbing behavior. The peptide showed only a tendency to increase dopamine release from striatal slices, while amphetamine elevated this significantly. The results suggest that the striatal dopamine system is involved in the behavioral action of beta-/Tyr9/melanotropin-/9-18/.