Aminopyridine block of transient potassium current.

Aminopyridine block of transient potassium current. The blocking action of 4-aminopyridine (4-AP) and 3, 4-diaminopyridine (Di-AP) on transient potassium current (IA) in molluscan central neurons was studied in internal perfusion voltage-clamp experiments. Identical blocking effects were seen when the drugs were applied either externally or internally. It was found that aminopyridines have two kinds of effects on IA channels. The first involves block of open channels during depolarizing pulses and results in a shortening of the time to peak current and an increase in the initial rate of decay of current. This effect of the drug is similar to the block of delayed potassium current by tetraethylammonium (TEA). The other effect is a steady block that increases in strength during hyperpolarization, is removed by depolarization, and is dependent on the frequency of stimulation. The voltage dependence of steady state block approximates the voltage dependence of inactivation gating a changes e-fold in approximately 10 mV. These data suggest that the strength of block may depend on the state of IA gating such that the resting state of the channel with open inactivation gate is more susceptible to block than are the open or inactivated states. A multistate sequential model for IA gating and voltage-dependent AP block is developed. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png The Journal of General Physiology Rockefeller University Press

Aminopyridine block of transient potassium current.

The Journal of General Physiology, Volume 80 (1): 1 – Jul 1, 1982

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Publisher
Rockefeller University Press
Copyright
© 1982 Rockefeller University Press
ISSN
0022-1295
eISSN
1540-7748
DOI
10.1085/jgp.80.1.1
Publisher site
See Article on Publisher Site

Abstract

The blocking action of 4-aminopyridine (4-AP) and 3, 4-diaminopyridine (Di-AP) on transient potassium current (IA) in molluscan central neurons was studied in internal perfusion voltage-clamp experiments. Identical blocking effects were seen when the drugs were applied either externally or internally. It was found that aminopyridines have two kinds of effects on IA channels. The first involves block of open channels during depolarizing pulses and results in a shortening of the time to peak current and an increase in the initial rate of decay of current. This effect of the drug is similar to the block of delayed potassium current by tetraethylammonium (TEA). The other effect is a steady block that increases in strength during hyperpolarization, is removed by depolarization, and is dependent on the frequency of stimulation. The voltage dependence of steady state block approximates the voltage dependence of inactivation gating a changes e-fold in approximately 10 mV. These data suggest that the strength of block may depend on the state of IA gating such that the resting state of the channel with open inactivation gate is more susceptible to block than are the open or inactivated states. A multistate sequential model for IA gating and voltage-dependent AP block is developed.

Journal

The Journal of General PhysiologyRockefeller University Press

Published: Jul 1, 1982

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