RT Journal Article
SR Electronic
T1 THE EFFECTS OF BARIUM ON THE ACTION POTENTIAL AND THE MEMBRANE CURRENT OF SHEEP HEART PURKINJE FIBERS
JF Journal of Pharmacology and Experimental Therapeutics
JO J Pharmacol Exp Ther
FD American Society for Pharmacology and Experimental Therapeutics
SP 418
OP 426
VO 185
IS 2
A1 SHIBATA, JIRO
YR 1973
UL http://jpet.aspetjournals.org/content/185/2/418.abstract
AB The effects of Ba++ on quiescent Purkinje fibers from sheep heart were examined using membrane potential recording and membrane current measurement by means of a voltage clamp. Depolarization was observed in either Na+ or Na+ -free solution containing 0.02 mM Ba++. The rate of depolarization was accelerated in the presence of Na+ and by repeated stimulation. Threshold potential was lowered and action potential duration was prolonged by Ba++. Changes caused by Ba++ were suppressed to some extent by Ca++. Inward currents found only in Na+-Tyrode's solution were increased and outward currents observed in Na+ -free Tyrode's solution were decreased by Ba++. The increased inward currents were more evident and lasted longer than the decreased outward current. The results suggest that the changes caused by Ba++ are mainly brought about by the increased Na+ current; a more detailed explanation of these changes is given by considering the competitive action between Ca++ and Ba++. © 1973 by The Williams & Wilkins Co.