Electrophysiological effects of cholecystokinin: central dopaminergic systems

The coexisting cholecystokinin (CCK)/dopamine (DA) neurons are located predominantly in the ventral tegmental area of the rat and project to the medial part of the nucleus accumbens (NAc). Iontophoretically applied CCK consistently activated presumed CCK/DA cells as well as those cells receiving CCK/DA projections in the medial NAc. Unsulfated CCK had little or no effect. The putative CCK antagonist proglumide selectively blocked the activation produced by CCK but not glutamate. DA also reversed CCK-induced excitation, presumably by its hyperpolarizing actions. These results suggest that CCK and DA may interact to influence the CCK/DA system.