Interaction of spin-labeled local anesthetics with the sodium channel of squid axon membranes

Howard H. Wang*, Jay Z. Yeh, Toshio Narahashi

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

12 Scopus citations


The effects of spin-labeled local anesthetics on sodium currents of internally perfused squid axons were studied using the voltage-clamp technique. Internal application (10 μm) of the most potent spin-labeled local anesthetic used in this study produced a small initial block of sodium currents. However, after sixty repetitive pulses (to +80 mV) given at 1 Hz, the sodium currents were drastically reduced. In addition to this frequency-dependent phenomenon, the anesthetic effect on the sodium currents was also sensitive to the voltage of the pulses. Both the frequency- and voltage-dependent properties remained intact after removal of sodium inactivation with pronase. The recovery of sodium currents from this frequency-dependent anesthetic effect followed a single exponential curve with a surprisingly long time constant of about 10 min. Such a long recovery time, which is longer than any known sodium inactivation process, led us to suggest that the recovery process represents the dissociation of drug molecules from their binding sites. We have also found that increasing hydrophobic character of the homologues series of spin-labeled local anesthetics enhances the frequency- and voltage-dependent block of sodium currents. This effect strongly suggests that hydrophobic interaction is an integral component of the binding site. These probes with their selective effects on the sodium currents, are expected to be highly useful in studying the molecular structure of the sodium channels.

Original languageEnglish (US)
Pages (from-to)227-233
Number of pages7
JournalThe Journal of Membrane Biology
Issue number1
StatePublished - Dec 1982


  • frequency dependence
  • local anesthetics
  • sodium channels
  • spin label
  • squid axon
  • voltage-clamp

ASJC Scopus subject areas

  • Biophysics
  • Physiology
  • Cell Biology


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