Behavioral interaction between endogenous opioids, CCK-8 and dopaminergic systems in the nucleus accumbens of rats.

Injection of apomorphine into the nucleus accumbens of rats elicits hypermotility, presumably by activating postsynaptically located dopamine receptor systems. This behavioral response is inhibited by local treatment with CCK-8 or gamma-endorphin. The action of both peptides is antagonized by intra-accumbal treatment with naloxone. These findings suggest that endogenous opioids are implicated in certain neuroleptic-like effects of CCK-8 and that in the nucleus accumbens a functional interaction exists between CCK-8, endogenous opioids and dopaminergic systems.