Non-Stationary Noise Analysis of M-Currents Simulated and Recorded in PC12
Cells.
Alvaro Villarroel.
Howard Hughes Medical Institute, Department of Neurobiology and Behavior,
SUNY at Stony Brook and Instituto Cajal, Avenida Dr. Arce 37, Madrid.
APStracts 4:0015N, 1997.
ABSTRACT
M-current relaxations recorded in PC-12 cells were subjected to non-stationary
noise analysis (NSNA) to obtain estimates of single channel current (i),
channel number (N) and open probability (po) for the channels responsible for
M-current. The analysis was constrained such that N and single channel
conductance were the same at two potentials. The relation between variance and
current indicated that the fraction of channels open was 0.58 ٌ 0.06 and 0.05
ٌ 0.04 (mean ٌ S.D.; n=9) at -33 mV and -63 mV, respectively. The single M-
channel conductance was 4.0 pS, and a density of 1 functional M-channel per 4
وو2 was estimated. Monte-Carlo simulations of a two state model of M-channels
were used to obtain sets of simulated macroscopic M-currents that were
subjected to the same NSNA procedure so as to evaluate the accuracy of M-
channel parameters obtained with this method. The influence of current rundown
and filter frequency on estimates of i, N, and po were evaluated. The single
channel parameters estimated from the simulations differed by less than 10 %
from actual values at any level of current rundown, number of channels or po.
The dispersion in the estimation of N and po increased as po decreased.
Decreasing filter frequency caused an underestimation of the single channel
current, paralleled by an overestimation of the number of channels. The
estimation of po was relatively immune to the filter frequency, especially for
data simulated with po = 0.77.
Received 12 July 1996; accepted in final form 16 December 1996.
APS Manuscript Number J548-6.
Article publication pending J. Neurophysiol.
ISSN 1080-4757 Copyright 1997 The American Physiological Society.
Published in APStracts on 21 January 1997