The Journal of Neuroscience, May 1, 2000, 20(9):3408-3414
Coregulation of Voltage-Dependent Kinetics of Na+ and
K+ Currents in Electric Organ
M. Lynne
McAnelly and
Harold H.
Zakon
Section of Neurobiology and Institute for Neuroscience, Patterson
Laboratory, The University of Texas at Austin, Austin, Texas 78712
The electric organ cells of Sternopygus generate
action potentials whose durations vary over a fourfold range. This
variation in action potential duration is the basis for individual
variation in a communication signal. Thus, action potential duration
must be precisely regulated in these cells. We had observed
previously that the inactivation kinetics of the electrocyte
Na+ current show systematic individual variation. In
this study, using a two-electrode voltage clamp, we found that the
voltage-dependent activation and deactivation kinetics of the delayed
rectifying K+ current in these cells covary in a
graded and predictable manner across fish. Furthermore, when
Na+ and K+ currents were recorded
in the same cell, their voltage-dependent kinetics were highly
correlated. This finding illustrates an unprecedented degree of
coregulation of voltage-dependent properties in two molecularly
distinct ionic channels. Such a coregulation of ionic channels is
uniquely observable in a cell specialized to generate individual
differences in electrical activity and in which the results of
biophysical control mechanisms are evident in behaving animals. We
propose that the precise coregulation of the voltage-dependent kinetics
of multiple ionic currents may be a general mechanism for regulation of
membrane excitability.
Key words:
Na+ current; K+
current; electric organ; voltage-clamp; electric fish; Sternopygus; regulation
Copyright © 2000 Society for Neuroscience 0270-6474/00/2093408-07$05.00/0
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