Cholecystokinin modulates mesolimbic dopaminergic influences on male rat copulatory behavior.

Much evidence suggests that the neuropeptide cholecystokinin (CCK) functions as a neurotransmitter or neuromodulator in the central nervous system. The CCKa receptor subtype in the nucleus accumbens has been demonstrated to potentiate the behavioral and neurophysiological effects of dopamine. Since the mesolimbic dopamine system participates in the regulation of male rat sexual behavior, the present investigation was undertaken to determine if central CCK modulates this dopaminergic regulation. Electrical stimulation of the ventral tegmental area greatly enhanced several measures of appetitive and consummatory male rat sexual behavior. Administration of a CCKa receptor antagonist to the posteromedian nucleus accumbens reversed the electrically stimulated behavioral enhancement. A CCKb antagonist was without effect. In a second group of animals, administration of either a CCKa or CCKb antagonist to the anterolateral nucleus accumbens reversed the enhancement of consummatory sexual responding produced by electrical stimulation. These results agree with the growing body of evidence supporting different behavioral roles for two distinct CCK systems in the nucleus accumbens.