Cholecystokinin potentiates dopamine-mediated behaviors in the nucleus accumbens, a site of CCK-DA co-existence

Cholecystokinin is an eight-amino acid peptide found in mammalian brain and gut. Recent immunocytochemical studies demonstrated colocalization of cholecystokinin (CCK) and dopamine (DA) in the mesolimbic pathway of the rat. To test the behavioral significance of the CCK-DA co-existence, we have microinfused CCK into the nucleus accumbens, alone or in combination with DA or apomorphine, and measured two standard dopaminergic behaviors, hyperlocomotion and stereotypy in rats. The data summarized above support the conclusion that CCK acts as a modulator of DA in the nucleus accumbens, since CCK had no effect when administered alone, but potentiated the behavioral effects of DA and apomorphine.