Biophysical Journal 63: 654-662 (1992)
© 1992 the Biophysical Society

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Liu, Y M Articles by Mazzanti, M Search for Related Content PubMed PubMed Citation Articles by Liu, Y M Articles by Mazzanti, M

Na channels that remain open throughout the cardiac action potential plateau.

Department of Anatomy and Cell Biology, Emory University School of Medicine, Atlanta, Georgia 30322.

ABSTRACT

In this paper we report the direct measurement of rare Na channel events that occur during the cardiac action potential, viz., channels that open at the upstroke and remain open throughout the plateau and early repolarization phase. The technique we use allows us to record channel activity and action potentials at the same time; thus, we are certain of when the Na channels open and when they finally close. The slow Na channels have the same voltage dependence, single-channel conductance, and TTX sensitivity as the fast Na channels, and they conduct Li. It therefore seems likely that the fast and the slow currents flow through the same channel. If this interpretation is correct, then the Na channel not only initiates the action potential but also helps to maintain its plateau. It is possible that the slow Na currents represent a separate collection of channels rather than a low-probability state of the fast Na channels. Regardless of which interpretation is correct, the present experiments allow us to assess the effect of the slow currents on action potential shape and on sustained Na entry.

This article has been cited by other articles:

				J. Magyar, C. E. Kiper, R. Dumaine, D. E. Burgess, T. Banyasz, and J. Satin Divergent action potential morphologies reveal nonequilibrium properties of human cardiac Na channels Cardiovasc Res, December 1, 2004; 64(3): 477 - 487. [Abstract] [Full Text] [PDF]

				T. Bohle, M. C. Brandt, M. Lindner, and D. J. Beuckelmann Identification of Gating Modes in Single Native Na+ Channels From Human Atrium and Ventricle Circ. Res., September 6, 2002; 91(5): 421 - 426. [Abstract] [Full Text] [PDF]

				A. C. Zygmunt, G. T. Eddlestone, G. P. Thomas, V. V. Nesterenko, and C. Antzelevitch Larger late sodium conductance in M cells contributes to electrical heterogeneity in canine ventricle Am J Physiol Heart Circ Physiol, August 1, 2001; 281(2): H689 - H697. [Abstract] [Full Text] [PDF]

				M. Zaniboni, A. E. Pollard, L. Yang, and K. W. Spitzer Beat-to-beat repolarization variability in ventricular myocytes and its suppression by electrical coupling Am J Physiol Heart Circ Physiol, March 1, 2000; 278(3): H677 - H687. [Abstract] [Full Text] [PDF]