Summary
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1.
Voltage clamp measurements were performed on single myelinated nerve fibres of the frog Xenopus laevis.
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2.
During long-lasting depolarizations the potassium current decayed in a fast phase with a time constant of about 0.6 sec and a following slow phase with a time constant between 3.6 (V=0) and 20 sec (V=100 mV).
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3.
The decay of the potassium current was the result of an inactivation of the potassium permeability and not of a shift of the potassium equilibrium potential as shown by experiments in isotonic KCl solution.
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4.
At a hyperpolarization of −20 mV the potassium inactivation was fully removed. It remained incomplete even at large depolarizations. The steady-state inactivation curve was S-shaped but not symmetrical.
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5.
The experimental results could be described by extending the Hodgkin-Huxley equations introducing two terms of potassium inactivation.
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This work was supported by the Deutsche Forschungsgemeinschaft.
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Schwarz, J.R., Vogel, W. Potassium inactivation in single myelinated nerve fibres of Xenopus laevis. Pflugers Arch. 330, 61–73 (1971). https://doi.org/10.1007/BF00588735
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DOI: https://doi.org/10.1007/BF00588735