In vivo electrochemical analysis of cholecystokinin-induced inhibition of dopamine release in the nucleus accumbens.

In vivo electrochemical techniques were used to study the effects of the sulfated (CCK8-S) and unsulfated (CCK8-US) forms of the cholecystokinin octapeptide on dopamine (DA) release in the nucleus accumbens. A dose-dependent inhibition of DA release was observed only with CCK8-S. This inhibitory effect was blocked by the CCK receptor antagonist proglumide, and was reversed by systemic injections of apomorphine. Given that apomorphine can hyperpolarize DA neurons, these data indicate that CCK may inhibit the release of DA by a process of depolarization block and suggest a mechanism by which CCK may regulate overactive mesolimbic DA transmission.