Abstract The release of immunoreactive cholecystokinin (CCK) and dopamine was monitored simultaneously from superfused rat striatal slices. Exposure of the tissue to medium containing elevated of dopamine (10 −7 and 10 −6)M), the dopamine agonist pergolide (10 −7, M), the D 2-antagonist sulpride (1 μM) or the D 1-antagonist (SCH 23390) had no significant effect on basal overflow or on evoked release of CCK. On the other hand, preincubation of striatal slices with d-amphetamine (10 −5 M) enhanced basal and veratrine-stimulated dopamine release but markedly suppressed evoked CCK release. Sulpiride blocked this action of amphetamine whereas SCH 23390 was ineffective. The data suggests that whereas it is difficult to observe any effects of exogenous dopamine agonists or antagonists on evoked CCK release, endogenously released dopamine appears to interact with D 2-receptors to suppress evoked CCK release from rat striatal slices.