The inhibition of sodium currents by quaternary derivatives of lidocaine was studied in single myelinated nerve fibers. Membrane currents were diminished little by external quaternary lidocaine (QX). QX present in the axoplasm (<0.5 mM) inhibited sodium currents by more than 90%. Inhibition occurred as the sum of a constant, tonic phase and a variable, voltage-sensitive phase. The voltage-sensitive inhibition was favored by the application of membrane potential patterns which produce large depolarizations when sodium channels are open. Voltage-sensitive inhibition could be reversed by small depolarizations which opened sodium channels. One explanation of this observation is that QX molecules enter open sodium channels from the axoplasmic side and bind within the channels. The voltage dependence of the inhibition by QX suggests that the drug binds at a site which is about halfway down the electrical gradient from inside to outside of the sodium channel.
Article| July 01 1973
The Inhibition of Sodium Currents in Myelinated Nerve by Quaternary Derivatives of Lidocaine
Gary R. Strichartz
From the Department of Physiology and Biophysics, University of Washington School of Medicine, Seattle, Washington 98195.
Dr. Strichartz's present address is the Department of Pharmacology, Yale University School of Medicine, New Haven, Connecticut 06510.
Received: July 14 1972
Online Issn: 1540-7748
Print Issn: 0022-1295
Copyright © 1973 by The Rockefeller University Press
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Gary R. Strichartz; The Inhibition of Sodium Currents in Myelinated Nerve by Quaternary Derivatives of Lidocaine . J Gen Physiol 1 July 1973; 62 (1): 37–57. doi: https://doi.org/10.1085/jgp.62.1.37
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