Giorguieff_1977_J.Pharmacol.Exp.Ther_200_535

Rat striatal slices (two) were superfused continuously with L-3,5-3H tyrosine and 3H-dopamine (3H-DA) release was estimated in serial fractions of superfusates. The spontaneous release of 3H-DA was reduced by about 50% when slices were superfused with a calcium-free medium containing ethylene glycol bis (beta-aminoethyl ether)- N,N'-tetraacetic acid (EGTA) (10(-4) M) or with a medium containg tetrodotoxin (5 x 10(-7) M). These effects were not related to a change in 3H-DA synthesis since the rate of L-3,5-3H tyrosine hydroxylation, as measured by 3H-H2O formation was not significantly reduced. Acetylcholine (ACh) (10(-5) M) stimulated the release of 3H-DA (about 100%). This effect was abolished in the absence of calcium; it was partially blocked by pempidine (10(-5) M), atropine (10(-6) M) or scopolamine (10(-5), 10(-6) M). Oxotremorine (10(-5) M) enhanced 3H-DA release but to a lesser extent (60%) than ACh (10(-5) M); its action was completely blocked by atropine (10(-6) M) and unaffected by pempidine (10(-5) M). The ACh- (10(-5) M) and oxotremorine- (10(-5) M) stimulatine effects on 3H-DA spontaneous release were still detected in slices superfused in the presence of tetrodotoxin (5 x 10(-7) M). In the presence of the neurotoxin, the effect of ACh (10(-5) M) was significantly reduced by pempidine (10(-5) M) and the effect of oxotremorine (10(-5) M) was blocked by atropine (10(-6) M). These results suggest the presence of cholinergic presynaptic receptors of the nicotinic and muscarinic types on striatal dopaminergic terminals.