An ion-site interaction model for sodium currents in the giant axon

M. Cohen-Armon*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


The time and voltage dependence of sodium currents in the Myxicola giant axon were examined as functions of the external sodium concentration. The results were incompatible with a model of free diffusion through a gated channel, but lent themselves to analysis in terms of a model involving a positive cooperative homotropic reaction in which Na+ interacts with two allosteric sites - a regulatory site and a transfer site - at the 'sodium channel'. The time-dependent solution of the rate equations describing the kinetics of the transfer reaction was derived as an expression describing the sodium current as a function of time membrane potential and external sodium concentration. This function was used to test the validity of the model by its ability to predict the nerve excitability properties. The predicted i-v and i-t curves fitted the experimental results (p < 0.005 and p < 0.05, respectively). The computed parameters of these functions are consistent with other experimental results. The possibility of a noncooperative reaction was rejected.

Original languageEnglish
Pages (from-to)285-298
Number of pages14
JournalBiophysical Chemistry
Issue number4
StatePublished - Nov 1984
Externally publishedYes


  • Cooperativity
  • Excitability
  • Giant axon
  • Na channel
  • Nerve membrane
  • Voltage clamp


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