In vivo electrochemical evidence for an enkephalinergic modulation underlying stereotyped behavior: reversibility by naloxone.

The effect of the enkephalin pentapeptide analog (WY 42,896) on amphetamine-induced stereotypy was studied in male, albino rats. WY 42,896 significantly inhibited amphetamine-induced stereotypy. The inhibition of the head-bobbing and sniffing components was significantly reversed by naloxone. Disinhibition of the rearing components by naloxone reached borderline significance. In vivo electrochemical measurements in rat caudate showed that WY 42,896 inhibited both basal and amphetamine-induced dopamine release. This inhibition was prevented by naloxone. These data show an enkephalinergic-dopaminergic interaction in rat striatum, both behaviorally and biochemically, and suggest a presynaptic site of action of the enkephalin on dopamine neurons.