Uniquely, gamma-endorphin induces an effect that is both opiate- and neuroleptic-like

Bilateral injection of gamma-endorphin into the nucleus accumbens of rats antagonizes the hyperlocomotion elicited by local treatment with relatively high doses of apomorphine. beta-Endorphin, alpha-endorphin, [Met]enkephalin, [Leu]enkephalin and des-Tyr1-gamma-endorphin do not mimic this effect of gamma-endorphin. Previous studies have shown that this antagonism by gamma-endorphin is mediated by a naloxone sensitive receptor system. It is concluded that uniquely, gamma-endorphin has an action that is both opiate- and neuroleptic-like.