EFFECTS OF SELECTIVE DOPAMINE-D2-RECEPTOR AGONISTS ON THE RELEASE OF CHOLECYSTOKININ-LIKE IMMUNOREACTIVITY FROM RAT NEOSTRIATUM

Whether or not the release of cholecystokinin-like immunoreactivity, from slices of rat caudatoputamen, could be modulated via dopamine D2-receptors was investigated. The release of immunoreactivity was stimulated by high concentrations of K+ (35-55 mM). The effects of 2 D2-selective dopaminergic agonists, RU 24926 [N-n-propyl-di-.beta.(3-hydroxyphenyl)-ethylaminohydrochloride] and LY 141865 [4,4a,5,6,7,8,8a,9-octahydro-5-propyl-2H-pyrazole-(3,4)-g-quinoline], were tested on the K+-induced release. Both agents enhanced the release of immunoreactivity in a concentration-dependent manner. The effect of RU 24926 was blocked by (-)-sulpiride and domperidone, 2 selective D2-antagonists. Stimulation of dopamine receptors of the D2-subtype enhances the release of cholecystokinin-like immunoreactivity from nerve endings in rat neostriatum.