Activation of muscarinic receptors on striatal synaptosomes increases the release of endogenous dopamine.

The release of endogenous dopamine was investigated using rat striatal synaptosomes in superfusion. Depolarization with 15 mM KC1 evoked a release which was totally calcium-dependent. Also, the basal release of dopamine was in part dependent on the presence of calcium ions. Exogenous acetylcholine potentiated the K+-induced release of endogenous dopamine through the activation of receptors of the muscarinic type located on dopamine nerve terminals. Very similar results were obtained when the release of 3H-dopamine, previously taken up into striatal synaptosomes, was examined.