title: Inhibitory effects of quinidine on rat heart muscarinic receptors.
abstract: Quinidine inhibited binding of the labelled agonist [3H]oxotremorine M [( 3H]Oxo-M) and the labelled antagonist [3H]N-methylscopolamine [( 3H]NMS) to rat heart muscarinic receptors. Kinetic studies demonstrated that quinidine decreased the association rates (I50: 4 and 7.5 microM) and dissociation rates (I50: 100 and 68 microM) of [3H]Oxo-M and [3H]NMS, with different potencies. These cooperative effects explained the low Hill coefficients and apparent selectivity of quinidine competition curves.
mesh_terms: D000818:Animals; D001285:Atropine / Q000378:metabolism; D001667:Binding, Competitive; D006321:Heart / Q000187:drug effects*; D007700:Kinetics; D008433:Mathematics; D009206:Myocardium / Q000378:metabolism*; D019832:N-Methylscopolamine; D010095:Oxotremorine / Q000378:metabolism; D011802:Quinidine / Q000494:pharmacology*; D051381:Rats; D011976:Receptors, Muscarinic / Q000187:drug effects* / Q000378:metabolism; D012602:Scopolamine Derivatives / Q000378:metabolism
chemical_list: D011976:Receptors, Muscarinic; D012602:Scopolamine Derivatives; D010095:Oxotremorine; D001285:Atropine; D011802:Quinidine; D019832:N-Methylscopolamine