title: The cholinomimetic agent bethanechol activates IK(ACh) in feline atrial myocytes.
abstract: The effect of the cholinomimetic agent, bethanechol on macroscopic membrane currents was studied in dispersed cat atrial myocytes, using the whole-cell patch-clamp technique. Bethanechol activated an inward rectifying potassium current similar to I(K(ACh)), and a delayed rectifying-like outward current, similar to I(KM3) activated by pilocarpine, choline, and tetramethylammonium, and I(KM4) activated by 4-aminopyridine. The relatively specific muscarinic receptors subtype antagonists methoctramine (M(2)), and tropicamide (M(4)) inhibited both current components induced by bethanechol, suggesting a lack of specificity of these antagonists on cat atrial myocytes. The specific antagonist of M(3) receptors, para-fluoro-hexahydro-siladifenidol did not significantly inhibit the bethanechol-induced currents. In addition, pretreatment with PTX prevented activation of the bethanechol-induced inward and outward currents, suggesting that M(3) receptors are probably not involved in the bethanechol action. The I(K(ACh)) specific blocker tertiapin inhibited both inward rectifying- and delayed rectifying-like currents. These results suggest that both current components result from activation of a single channel type, likely I(K(ACh)).
authors.affiliation: Facultad de Medicina Humana y Ciencias de la Salud, Universidad Autónoma de Zacatecas, Zacatecas, México.
authors.forename: Dora E
authors.initials: DE
authors.lastname: Benavides-Haro
authors.forename: Ricardo A
authors.initials: RA
authors.lastname: Navarro-Polanco
authors.forename: José A
authors.initials: JA
authors.lastname: Sánchez-Chapula
mesh_terms: D000818:Animals; D001464:Barium / Q000494:pharmacology; D001514:Bee Venoms / Q000494:pharmacology; D001569:Benzodiazepines / Q000494:pharmacology; D018723:Bethanechol / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D002415:Cats; D018678:Cholinergic Agents / Q000494:pharmacology*; D003959:Diamines / Q000494:pharmacology; D006325:Heart Atria / Q000166:cytology; D066298:In Vitro Techniques; D008564:Membrane Potentials / Q000187:drug effects; D018721:Muscarinic Agonists / Q000494:pharmacology; D018727:Muscarinic Antagonists / Q000494:pharmacology; D032342:Muscle Cells / Q000187:drug effects / Q000378:metabolism*; D010627:Phenethylamines / Q000494:pharmacology; D010880:Piperidines / Q000494:pharmacology; D026902:Potassium Channel Blockers / Q000494:pharmacology; D024661:Potassium Channels, Inwardly Rectifying / Q000819:agonists*; D043643:Receptor, Muscarinic M1 / Q000187:drug effects; D043585:Receptor, Muscarinic M2 / Q000187:drug effects; D043587:Receptor, Muscarinic M3 / Q000187:drug effects; D043588:Receptor, Muscarinic M4 / Q000187:drug effects; D013449:Sulfonamides / Q000494:pharmacology; D014331:Tropicamide / Q000494:pharmacology
chemical_list: D001514:Bee Venoms; D018678:Cholinergic Agents; D003959:Diamines; C115921:L 735821; D018721:Muscarinic Agonists; D018727:Muscarinic Antagonists; D010627:Phenethylamines; D010880:Piperidines; D026902:Potassium Channel Blockers; D024661:Potassium Channels, Inwardly Rectifying; D043643:Receptor, Muscarinic M1; D043585:Receptor, Muscarinic M2; D043587:Receptor, Muscarinic M3; D043588:Receptor, Muscarinic M4; D013449:Sulfonamides; D018723:Bethanechol; C058297:4-fluorohexahydrosiladifenidol; D001569:Benzodiazepines; D001464:Barium; C029738:tertiapin; D014331:Tropicamide; C054938:methoctramine; C063533:dofetilide