Presynaptic muscarinic receptor activation enhances striatal dopamine release evoked by depolarization but not that induced by non-depolarizing stimuli

The release of ³H]dopamine stimulated by depolarization with 15 mM KCl of superfused rat striatal synaptosomes was potentiated by acetylcholine through the activation of presynaptic muscarinic receptors. In contrast, acetylcholine did not potentiate the release of ³H]dopamine elicited by d-amphetamine nor that caused by the calcium ionophore A23187. The dopamine carrier blocker nomifensine prevented the releasing action of amphetamine but not that of acetylcholine. The results suggest that the activation of muscarinic receptors on dopamine terminals in the rat corpus striatum selectively affects the calcium-dependent depolarization-induced release of the ³H]catecholamine. Moreover, the ³H]dopamine release caused by acetylcholine seems to occur independently of the membrane dopamine carrier.