COLECYSTOKININ OCTAPEPTIDE MODULATES DOPAMINE RELEASE IN RAT STRIATUM

The effect of cholecystokinin octapeptide sulfated (CCK8S) on the basa l and electrically evoked release of [H-3]dopamine ([H-3]DA) in striat al slices from the rat brain was studied. Cholecystokinin octapeptide did not influence the basal release of [H-3]DA. Field electrical stimu lation (FES) (2 Hz) induced an increase of dopamine release from stria tal slices, which was Ca2+ dependent and was abolished by tetrodotoxin , 10(-6) M. Cholecystokinin octapeptide (10(-9) M, 10(-8) M and 10(-7) M) dose dependently reduced the electrically evoked release of [H-3]D A. This effect was antagonized by the CCK-A receptor antagonists loxig lumide(10(-7) M, 10(-6) M and 10(-5) M) or proglumide (10(-5) M, 10(-4 ) M and 10(-3) M). The results suggest that CCK receptors type A are i nvolved in this effect of CCK8S in the striatum.