title: Electrophysiologic and voltage clamp analysis of the effects of sotalol on isolated cardiac muscle and Purkinje fibers.
abstract: The effect of dl-, d- and I-sotalol on electrophysiologic characteristics of guinea-pig papillary muscles, sheep and rabbit Purkinje fibers was studied. Standard electrophysiologic and voltage clamp techniques were used. At concentrations between 10(-6) and 10(-4) M, the main effect of sotalol consisted of prolongation of the action potential duration. In voltage clamp experiments this effect correlated with a substantial reduction of the time-dependent K current activated during the plateau of the action potential and a small reduction of the background K current. At concentrations above 10(-4) M, a secondary shortening of the action potential concomitant with a fall in maximal rate of depolarization was seen. In voltage clamp experiments this effect correlated with a decrease of a slowly inactivating Na current. In the absence of catecholamines d- and I-sotalol exerted identical effects on action potentials and voltage clamp currents.
mesh_terms: D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D004594:Electrophysiology; D006168:Guinea Pigs; D006321:Heart / Q000187:drug effects*; D066298:In Vitro Techniques; D007545:Isoproterenol / Q000494:pharmacology; D010210:Papillary Muscles / Q000187:drug effects; D011188:Potassium / Q000502:physiology; D011690:Purkinje Fibers / Q000187:drug effects; D011817:Rabbits; D012756:Sheep; D012964:Sodium / Q000502:physiology; D013015:Sotalol / Q000494:pharmacology*; D013997:Time Factors
chemical_list: D012964:Sodium; D013015:Sotalol; D007545:Isoproterenol; D011188:Potassium