title: Desensitization of the muscarinic receptor in the mammalian atrial myocardium.
abstract: Action potentials of constantly driven isolated trabeculae of the rabbit's atrial myocardium, being depressed by acetylcholine (ACh) at concentrations between 0.2 and 20 mumol/l, recovered during a constant drug application. The sensitivity of the atrial myocardium to ACh after a prolonged drug application was decreased but found to be restored about 7 min after switching off the ACh superfusion. The recovery during drug application was accelerated in Ca++ excess solutions but decelerated in K+ excess solutions. All the effects of ACh were blocked by atropine (1 mumol/l) completely. The results suggest that the muscarinic ACh receptor in the mammalian myocardium, responsible for the electrotropic effects, shows desensitization to ACh similar to the nicotinic receptor in other tissues.
mesh_terms: D000109:Acetylcholine / Q000494:pharmacology*; D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D006145:Guanethidine / Q000494:pharmacology; D066298:In Vitro Techniques; D009206:Myocardium / Q000378:metabolism*; D011433:Propranolol / Q000494:pharmacology; D011817:Rabbits; D011976:Receptors, Muscarinic / Q000187:drug effects* / Q000378:metabolism; D014403:Tubocurarine / Q000494:pharmacology
chemical_list: D011976:Receptors, Muscarinic; D011433:Propranolol; D000109:Acetylcholine; D014403:Tubocurarine; D006145:Guanethidine