The effects of external sodium and potassium concentration on the membrane potential of atrioventricular fibers of the toad.
Intracellular records were made from fibers in the A-V conducting system of isolated toad hearts. The A-V region was perfused with Ringer's solution of various K and Na concentrations. Resting potential in 2.8 mM [K]o was about 60 mv. Over the range 0.28 to 28 mM, resting potential diminished with increasing [K]o. Spontaneous action potentials appeared when [K]o was increased to 11.2 mM, and when resting potential had fallen to about 40 to 50 mv. Changes in [Na]o over the range 22 to 110 mM had a little effect on resting potential, but there was a linear relation between the peak value of the action potential and log [Na]o. Wenckebach periodicity was observed when [Na]o was lowered.
Kanno
T
T
Department of Physiology, Faculty of Medicine, University of Tokyo, Bunkyo-ku, Tokyo, Japan.
Matsuda
K
K
D000200:Action Potentials / Q000187:drug effects*; D000818:Animals; D001283:Atrioventricular Node / Q000166:cytology / Q000187:drug effects* / Q000502:physiology*; D002025:Bufonidae; D004305:Dose-Response Relationship, Drug; D066298:In Vitro Techniques; D007552:Isotonic Solutions / Q000494:pharmacology; D011188:Potassium / Q000494:pharmacology*; D000077331:Ringer's Solution; D012964:Sodium / Q000494:pharmacology*
D007552:Isotonic Solutions; D000077331:Ringer's Solution; D012964:Sodium; D011188:Potassium