A kinetic model for the muscarinic action of acetylcholine.
The timecourse of the membrane hyperpolarization evoked by stimulation of postganglionic parasympathetic nerve endings in isolated atria from the guinea-pig heart is mainly governed by two exponentials, one describing most of the rising phase (rate constant k alpha = 2.88+/-1.135 s-1) and one which completely describes the decline of the response (k beta = 0.58+/-0.31 s-1). An exact description of the muscarinic receptor mediated potential change, which also allows for its apparent latency and its s-shaped beginning, is found if two additional faster exponentials are introduced. In agreement with earlier results a model of four consecutive reactions is presented. It is concluded that during muscarinic cholinergic transmission reactions subsequent to binding of the ACh-molecules to the receptor are rate-limiting.
D000109:Acetylcholine / Q000502:physiology*; D000818:Animals; D004558:Electric Stimulation; D006168:Guinea Pigs; D006325:Heart Atria / Q000294:innervation*; D066298:In Vitro Techniques; D007700:Kinetics; D008954:Models, Biological; D010275:Parasympathetic Nervous System / Q000502:physiology; D011950:Receptors, Cholinergic / Q000502:physiology*; D011976:Receptors, Muscarinic / Q000502:physiology*
D011950:Receptors, Cholinergic; D011976:Receptors, Muscarinic; D000109:Acetylcholine