The Journal of General Physiology, Vol 68, 551-562, Copyright © 1976 by The Rockefeller University Press
Permeability of the sodium channel in Myxicola to organic cations
L Binstock
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 greater than hydroxylamine greater than
hydrazine greater than ammonium greater than guanidine greater than
formamidine greater than aminoguanidine greater than 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.