title: Involvement of cholinergic presynaptic receptors of nicotinic and muscarinic types in the control of the spontaneous release of dopamine from striatal dopaminergic terminals in the rat.
abstract: 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.
mesh_terms: D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D001285:Atropine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D003342:Corpus Striatum / Q000378:metabolism*; D004298:Dopamine / Q000378:metabolism*; D006900:Hydroxylation; D066298:In Vitro Techniques; D010095:Oxotremorine / Q000494:pharmacology; D010393:Pempidine / Q000494:pharmacology; D051381:Rats; D011950:Receptors, Cholinergic / Q000378:metabolism*; D012601:Scopolamine / Q000494:pharmacology; D013779:Tetrodotoxin / Q000494:pharmacology; D014443:Tyrosine / Q000378:metabolism
chemical_list: D011950:Receptors, Cholinergic; D014443:Tyrosine; D013779:Tetrodotoxin; D010095:Oxotremorine; D001285:Atropine; D012601:Scopolamine; D010393:Pempidine; D000109:Acetylcholine; D002118:Calcium; D004298:Dopamine