The double sucrose-gap voltage-clamp technique was applied to frog atrial tissue to investigate the ionic currents responsible for the action potential in this tissue. Membrane depolarization elicited two distinct components of inward current when the test node was exposed to normal Ringer solution: a fast inward current and a slow inward current. The fast inward current appeared to be carried by sodium ions, since it was rapidly abolished by exposure of the fiber to Na+-free solution or tetrodotoxin but persisted on exposure to Ca++-free solution. In contrast, in the majority of the preparations the slow inward current appeared to be primarily carried by calcium ions, since it was abolished on exposure of the fiber to Ca++-free solution but persisted on exposure to Na+-free solution. Action potential data supported the voltage-clamp findings. The normal action potential shows two distinct components in the upstroke phase: an initial rapid phase of depolarization followed by a slower phase of depolarization reaching the peak of the action potential. Abolition of the fast inward current resulted in abolition of the initial rapid phase of depolarization. Abolition of the slow inward current resulted in abolition of the slow phase of depolarization. These data support the hypothesis that two distinct and different ionic mechanisms contribute to the upstroke phase of the action potential in frog atrial tissue.
Skip Nav Destination
Article navigation
Article|
November 01 1971
Two Inward Currents in Frog Atrial Muscle
Merrill Tarr
Merrill Tarr
From the Department of Physiology, University of Kansas Medical Center, Kansas City, Kansas 66103
Search for other works by this author on:
Merrill Tarr
From the Department of Physiology, University of Kansas Medical Center, Kansas City, Kansas 66103
Received:
April 01 1971
Online ISSN: 1540-7748
Print ISSN: 0022-1295
Copyright © 1971 by The Rockefeller University Press
1971
J Gen Physiol (1971) 58 (5): 523–543.
Article history
Received:
April 01 1971
Citation
Merrill Tarr; Two Inward Currents in Frog Atrial Muscle . J Gen Physiol 1 November 1971; 58 (5): 523–543. doi: https://doi.org/10.1085/jgp.58.5.523
Download citation file:
Suggested Content
Properties of "creep currents" in single frog atrial cells.
J Gen Physiol (June,1986)
"Creep currents" in single frog atrial cells may be generated by electrogenic Na/Ca exchange.
J Gen Physiol (June,1986)
Ionic currents in single isolated bullfrog atrial cells.
J Gen Physiol (February,1983)
Email alerts
Advertisement