Biophysical Journal 66: 1853-1863 (1994)
© 1994 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 Correa, A M Articles by Bezanilla, F Search for Related Content PubMed PubMed Citation Articles by Correa, A M Articles by Bezanilla, F

Gating of the squid sodium channel at positive potentials. I. Macroscopic ionic and gating currents.

Department of Physiology, School of Medicine, University of California at Los Angeles 90024.

ABSTRACT

Macroscopic ionic sodium currents and gating currents were studied in voltage-clamped, dialyzed giant axons of the squid Loligo pealei under conditions of regular and inverse sodium gradients. Sodium currents showed regular kinetics but inactivation was incomplete, showing a maintained current for depolarizations lasting 18 ms. The ratio of the maintained current to the peak current increased with depolarization and it did not depend on the direction of the current flow or the sodium gradient. The time constant of inactivation was not affected by the sodium gradient. Double-pulse experiments allowed the separation of a normal inactivating component and a noninactivating component of the sodium currents. In gating current experiments, the results from double-pulse protocols showed that the charge was decreased by the prepulse and that the slow component of the 'on' gating current was preferentially depressed. As expected, charge immobilization was established faster at higher depolarizations than at low depolarizations, however, the amount of immobilized charge was unaffected by the pulse amplitude. This indicates that the incomplete sodium inactivation observed at high depolarizations is not the result of decreased charge immobilization; the maintained current must be due to a conductance that appears after normal charge immobilization and fast inactivation.

This article has been cited by other articles:

				R. F. Rakowski, D. C. Gadsby, and P. De Weer Single Ion Occupancy and Steady-state Gating of Na Channels in Squid Giant Axon J. Gen. Physiol., February 22, 2002; 119(3): 235 - 250. [Abstract] [Full Text] [PDF]

				J. C. McPhee, D. S. Ragsdale, T. Scheuer, and W. A. Catterall A Critical Role for Transmembrane Segment IVS6 of the Sodium Channel [IMAGE] Subunit in Fast Inactivation J. Biol. Chem., May 19, 1995; 270(20): 12025 - 12034. [Abstract] [Full Text] [PDF]