Overflow of dopamine and cholecystokinin in rat nucleus accumbens in response to acute drug administration.

Cholecystokinin octapeptide (CCK-8) coexists with dopamine (DA) in rat mesencephalic neurons that project to the nucleus accumbens. To obtain indices of corelease, microdialysis probes were placed in the posterior nucleus accumbens of anesthetized rats, which were then injected acutely (s.c.) with drugs that exert known effects on DA neuronal function. Microdialysis samples were assayed for DA and CCK-8 to determine the differential overflow of these cotransmitters in response to drug treatment. Haloperidol (0.5 mg/kg), d-amphetamine (1 mg/kg), and TCP (5 mg/kg) preferentially increased DA overflow, whereas morphine (5 mg/kg) elicited marked increases in the overflow of both DA and CCK-8. These results suggest that the release of accumbal DA and CCK-8 can be differentially regulated by drug treatment. Copyright 2000 Wiley-Liss, Inc.