Displacement currents in the node of Ranvier - Voltage and time dependence

W. Nonner, E. Rojas, R. Stämpfli

Research output: Contribution to journalArticle

57 Scopus citations

Abstract

The time course of the membrane currents in the node of Ranvier in which the sodium and potassium conductances have been blocked reveals asymmetries during and after the application of depolarizing and hyperpolarizing voltage-clamp pulses of identical size. Since, 1. the integrals of the "on" and "off" current transients were found to be equal and opposite, 2. the charge displaced reached saturation (about 140·10-15 C/node) when the internal potential was taken to a sufficiently positive value during the depolarizing pulses and, 3. the size of the charge transferred was unaffected by temperature although its time constant had a large temperature coefficient (Q10=2.4), these currents to our opinoon must result from charge movements confined to the membrane and, therefore, can be considered as non-linear displacement currents. The steady-state rearrangement of the charges is consistent with a Boltzmann distribution of charges (effective valence z′=1.65) between two configurations characterized by different energy levels. The midpoint potential of the distribution curve is -33.7 mV and its maximum slope, kT/z′e, is 14.9 mV. Following changes in membrane potential the charges undergo a first order transition between these states. We propose that these displacement currents arise from a redistribution of the charges involved in the sodium gating system.

Original languageEnglish (US)
Pages (from-to)1-18
Number of pages18
JournalPflügers Archiv European Journal of Physiology
Volume354
Issue number1
DOIs
StatePublished - Mar 1 1975

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Keywords

  • Gating Currents
  • Ranvier Node
  • Voltage Clamp

ASJC Scopus subject areas

  • Physiology

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