Search tips
Search criteria 


Logo of jgenphysiolHomeEditorsContactInstructions for Authors
J Gen Physiol. 1976 August 1; 68(2): 111–125.
PMCID: PMC2228421

Sodium channel selectivity. Dependence on internal permeant ion concentration


The selectivity of sodium channels in squid axon membranes was investigated with widely varying concentrations of internal ions. The selectivity ratio, PNa/PK, determined from reversal potentials decreases from 12.8 to 5.7 to 3.5 as the concentration of internal potassium is reduced from 530 to 180 to 50 mM, respectively. The internal KF perfusion medium can be diluted by tetramethylammonium (TMA), Tris, or sucrose solutions with the same decrease in PNa/PK. The changes in the selectivity ratio depend upon internal permeant ion concentration rather than ionic strength, membrane potential, or chloride permeability. Lowering the internal concentration of cesium, rubidium, guanidnium, or ammonium also reduces PNa/Pion. The selective sequence of the sodium channel is: Na greater than guanidinium greater than ammonium greater than K greater than Rb greater than Cs.

Full Text

The Full Text of this article is available as a PDF (754K).

Selected References

These references are in PubMed. This may not be the complete list of references from this article.
  • Armstrong CM, Bezanilla F. Charge movement associated with the opening and closing of the activation gates of the Na channels. J Gen Physiol. 1974 May;63(5):533–552. [PMC free article] [PubMed]
  • Armstrong CM, Bezanilla F, Rojas E. Destruction of sodium conductance inactivation in squid axons perfused with pronase. J Gen Physiol. 1973 Oct;62(4):375–391. [PMC free article] [PubMed]
  • Atwater I, Bezanilla F, Rojas E. Sodium influxes in internally perfused squid giant axon during voltage clamp. J Physiol. 1969 May;201(3):657–664. [PubMed]
  • Baker PF, Hodgkin AL, Ridgway EB. Depolarization and calcium entry in squid giant axons. J Physiol. 1971 Nov;218(3):709–755. [PubMed]
  • Begenisich T, Lynch C. Effects of internal divalent cations on voltage-clamped squid axons. J Gen Physiol. 1974 Jun;63(6):675–689. [PMC free article] [PubMed]
  • Binstock L, Lecar H. Ammonium ion currents in the squid giant axon. J Gen Physiol. 1969 Mar;53(3):342–361. [PMC free article] [PubMed]
  • Chandler WK, Meves H. Voltage clamp experiments on internally perfused giant axons. J Physiol. 1965 Oct;180(4):788–820. [PubMed]
  • Heckmann K. Single file diffusion. Biomembranes. 1972;3:127–153. [PubMed]
  • Hille B. Pharmacological modifications of the sodium channels of frog nerve. J Gen Physiol. 1968 Feb;51(2):199–219. [PMC free article] [PubMed]
  • Hille B. The permeability of the sodium channel to organic cations in myelinated nerve. J Gen Physiol. 1971 Dec;58(6):599–619. [PMC free article] [PubMed]
  • Hille B. The permeability of the sodium channel to metal cations in myelinated nerve. J Gen Physiol. 1972 Jun;59(6):637–658. [PMC free article] [PubMed]
  • Hille B. Ionic selectivity, saturation, and block in sodium channels. A four-barrier model. J Gen Physiol. 1975 Nov;66(5):535–560. [PMC free article] [PubMed]
  • HODGKIN AL, HUXLEY AF. Currents carried by sodium and potassium ions through the membrane of the giant axon of Loligo. J Physiol. 1952 Apr;116(4):449–472. [PubMed]
  • HODGKIN AL, KATZ B. The effect of sodium ions on the electrical activity of giant axon of the squid. J Physiol. 1949 Mar 1;108(1):37–77. [PubMed]
  • Keynes RD, Rojas E. Kinetics and steady-state properties of the charged system controlling sodium conductance in the squid giant axon. J Physiol. 1974 Jun;239(2):393–434. [PubMed]
  • Moore JW, Anderson N, Blaustein M, Takata M, Lettvin JY, Pickard WF, Bernstein T, Pooler J. Alkali cation selectivity of squid axon membrane. Ann N Y Acad Sci. 1966 Jul 14;137(2):818–829. [PubMed]
  • Narahashi T. Chemicals as tools in the study of excitable membranes. Physiol Rev. 1974 Oct;54(4):813–889. [PubMed]

Articles from The Journal of General Physiology are provided here courtesy of The Rockefeller University Press