Presynaptic muscarinic receptors increase striatal dopamine release evoked by "quashi-physiological" depolarization

The effects of acetylcholine on the release of [3H]dopamine was studied in superfused rat striatal synaptosomes prelabeled with the radioactive amine. The results confirm the presence of muscarinic presynaptic receptors mediating potentiation of the spontaneous release of the catecholamine. However, under depolarizing conditions, the release of dopamine evoked by 15 mM KC1 was increased by the activation of muscarinic receptors and not decreased, as previously found in striatal synaptosomes or slices depolarized with higher (50-60 mM) KC1 concentrations.