Weiler_1989_EXS_57_204

Two classical and two nonclassical muscarinic agents were tested for their effects on neostriatal acetylcholine (ACh) release. The classical muscarinic antagonist, atropine (0.1-2 microM), increased ACh release in a dose-dependent fashion, whereas the 'nonclassical' antagonist, pirenzepine (2-200 microM), had no effect on ACh release. The muscarinic agonist, oxotremorine (1-100 microM), and its analog, oxotremorine-M (0.1-50 microM), both decreased ACh release in a dose-dependent fashion. The inhibitory potency of oxotremorine-M was approximately 20 times that of oxotremorine, and the inhibitory effects of both agonists were blocked by atropine. The results obtained with the muscarinic antagonists indicate that 'M-2 type' muscarinic receptors mediate ACh release in the neostriatum, but further pharmacological analyses are required to assign with certainty the receptor subtype involved in neostriatal ACh release.