D2 DOPAMINE-RECEPTOR ACTIVATION INHIBITS BASAL AND FORSKOLIN-EVOKED ACETYLCHOLINE-RELEASE FROM DISSOCIATED STRIATAL CHOLINERGIC INTERNEURONS

We tested whether D2 ligands inhibit basal and forskolin-stimulated [H -3]ACh release from dissociated striata, as opposed to striatal slices . Quinpirole inhibited both basal (40% maximal inhibition; IC50 approx imate to 50 nM) and 10 mu M forskolin-stimulated release (80% inhibiti on; IC50 approximate to 25 nM quinpirole) and both actions were blocke d by a D2 antagonist. Vesamicol prevented the quinpirole and forskolin actions. The ability of D2 agonists to inhibit basal and cyclase-stim ulated acetylcholine release emanating from vesamicol-sensitive vesicl es appears to be tonically suppressed by inhibitory elements within st riatal circuitry.