Permeability of the sodium channel in Myxicola to organic cations

Abstract

The relative permeability of sodium channels to organic cations was determined in the Myxicola giant axon. Ionic currents under potential control were measured in seawater and in sodium-free solutions containing the organic cation. The measured reversal potential and the Goldman equation were used to obtain the relative permeabilities. The permeability sequence was found to be: sodium > hydroxylamine > hydrazine > ammonium > guanidine > formamidine > aminoguanidine > methylamine. Measurements were also made on sodium and several of the organic cations at different concentrations. The relative permeabilities of the ions were found to be independent of concentration. Qualitatively, the permeability sequence for the Myxicola giant axon was similar to that of the frog node of Ranvier. © 1976, Rockefeller University Press., All rights reserved.