|
|
|
|
|
|
|
||
The Journal of General Physiology, Vol 94, 279-301, Copyright © 1989 by The Rockefeller University Press
ARTICLES |
JB Patlak and M Ortiz
Department of Physiology and Biophysics, University of Vermont, Burlington 05405.
Individual Na+ channels of dissociated frog skeletal muscle cells at 10 degrees C fail to inactivate in 0.02% of depolarizing pulses, thus producing bursts of openings lasting hundreds of milliseconds. We present here a kinetic analysis of 87 such bursts that were recorded in multi-channel patches at four pulse potentials. We used standard dwell- time histograms as well as fluctuation analysis to analyze the gating kinetics of the bursting channels. Since each burst contained only 75- 150 openings, detailed characterization of the kinetics from single bursts was not possible. Nevertheless, at this low kinetic resolution, the open and closed times could be well fitted by single exponentials (or Lorentzians for the power spectra). The best estimates of both the open and closed time constants produced by either technique were much more broadly dispersed then expected from experimental or analytical variability, with values varying by as much as an order of magnitude. Furthermore, the values of the open and closed time constants were not significantly correlated with one another from burst to burst. The bursts thus expressed diverse kinetic behaviors, all of which appear to be manifestations of a single type of Na+ channel. Although the opening and closing rates were dispersed, their average values were close to those of alpha m and 2 beta m derived from fits to the early transient Na+ currents over the same voltage range. We propose a model in which the channel has both primary states (e.g., open, closed, and inactivated), as well as "modes" that are associated with independent alterations in the rate constants for transition between each of these primary states.
CiteULike 
Complore 
Connotea 
Del.icio.us 
Digg 
Reddit 
Technorati What's this?
This article has been cited by other articles:
|
|
 |
|
  G. N. Filatov, M. J. Pinter, and M. M. Rich Resting Potential-dependent Regulation of the Voltage Sensitivity of Sodium Channel Gating in Rat Skeletal Muscle In Vivo J. Gen. Physiol., July 25, 2005; 126(2): 161 - 172. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 J. Magistretti, D. S. Ragsdale, and A. Alonso Kinetic Diversity of Single-Channel Burst Openings Underlying Persistent Na+ Current in Entorhinal Cortex Neurons Biophys. J., November 1, 2003; 85(5): 3019 - 3034. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 D Naranjo and P Brehm Modal shifts in acetylcholine receptor channel gating confer subunit-dependent desensitization Science, June 18, 1993; 260(5115): 1811 - 1814. [Abstract] [PDF]
|
|
|
|
