Skip to main content
The Journal of General Physiology logoLink to The Journal of General Physiology
. 1972 Jun 1;59(6):659–675. doi: 10.1085/jgp.59.6.659

Inactivation of the Sodium Current in Myxicola Giant Axons

Evidence for coupling to the activation process

L Goldman 1, C L Schauf 1
PMCID: PMC2203206  PMID: 5025744

Abstract

Experiments were conducted on Myxicola giant axons to determine if the sodium activation and inactivation processes are coupled or independent. The main experimental approach was to examine the effects of changing test pulses on steady-state inactivation curves. Arguments were presented to show that in the presence of a residual uncompensated series resistance the interpretation of the results depends critically on the manner of conducting the experiment. Analytical and numerical calculations were presented to show that as long as test pulses are confined to an approximately linear negative conductance region of the sodium current-voltage characteristic, unambiguous interpretations can be made. When examined in the manner of Hodgkin and Huxley, inactivation in Myxicola is quantitatively similar to that described by the h variable in squid axons. However, when test pulses were increased along the linear negative region of the sodium current-voltage characteristic, steady-state inactivation curves translate to the right along the voltage axis. The shift in the inactivation curve is a linear function of the ratio of the sodium, conductance of the test pulses, showing a 5.8 mv shift for a twofold increase in conductance. An independent line of evidence indicated that the early rate of development of inactivation is a function of the rise of the sodium conductance.

Full Text

The Full Text of this article is available as a PDF (794.8 KB).

Selected References

These references are in PubMed. This may not be the complete list of references from this article.

  1. Binstock L., Goldman L. Current- and voltage-clamped studies on Myxicola giant axons. Effect of tetrodotoxin. J Gen Physiol. 1969 Dec;54(6):730–740. doi: 10.1085/jgp.54.6.730. [DOI] [PMC free article] [PubMed] [Google Scholar]
  2. Binstock L., Goldman L. Rectification in instantaneous potassium current-voltage relations in Myxicola giant axons. J Physiol. 1971 Sep;217(3):517–531. doi: 10.1113/jphysiol.1971.sp009583. [DOI] [PMC free article] [PubMed] [Google Scholar]
  3. COLE K. S., MOORE J. W. Liquid junction and membrane potentials of the squid giant axon. J Gen Physiol. 1960 May;43:971–980. doi: 10.1085/jgp.43.5.971. [DOI] [PMC free article] [PubMed] [Google Scholar]
  4. Chandler W. K., Hodgkin A. L., Meves H. The effect of changing the internal solution on sodium inactivation and related phenomena in giant axons. J Physiol. 1965 Oct;180(4):821–836. doi: 10.1113/jphysiol.1965.sp007733. [DOI] [PMC free article] [PubMed] [Google Scholar]
  5. Chandler W. K., Meves H. Voltage clamp experiments on internally perfused giant axons. J Physiol. 1965 Oct;180(4):788–820. doi: 10.1113/jphysiol.1965.sp007732. [DOI] [PMC free article] [PubMed] [Google Scholar]
  6. Goldman L., Binstock L. Current separations in Myxicola giant axons. J Gen Physiol. 1969 Dec;54(6):741–754. doi: 10.1085/jgp.54.6.741. [DOI] [PMC free article] [PubMed] [Google Scholar]
  7. HODGKIN A. L., HUXLEY A. F. A quantitative description of membrane current and its application to conduction and excitation in nerve. J Physiol. 1952 Aug;117(4):500–544. doi: 10.1113/jphysiol.1952.sp004764. [DOI] [PMC free article] [PubMed] [Google Scholar]
  8. HODGKIN A. L., HUXLEY A. F., KATZ B. Measurement of current-voltage relations in the membrane of the giant axon of Loligo. J Physiol. 1952 Apr;116(4):424–448. doi: 10.1113/jphysiol.1952.sp004716. [DOI] [PMC free article] [PubMed] [Google Scholar]
  9. HODGKIN A. L., HUXLEY A. F. The dual effect of membrane potential on sodium conductance in the giant axon of Loligo. J Physiol. 1952 Apr;116(4):497–506. doi: 10.1113/jphysiol.1952.sp004719. [DOI] [PMC free article] [PubMed] [Google Scholar]
  10. HOYT R. C. THE SQUID GIANT AXON. MATHEMATICAL MODELS. Biophys J. 1963 Sep;3:399–431. doi: 10.1016/s0006-3495(63)86829-0. [DOI] [PMC free article] [PubMed] [Google Scholar]
  11. Hoyt R. C., Adelman W. J., Jr Sodium inactivation. Experimental test of two models. Biophys J. 1970 Jul;10(7):610–617. doi: 10.1016/S0006-3495(70)86323-8. [DOI] [PMC free article] [PubMed] [Google Scholar]
  12. Hoyt R. C. Sodium inactivation in nerve fibers. Biophys J. 1968 Oct;8(10):1074–1097. doi: 10.1016/S0006-3495(68)86540-3. [DOI] [PMC free article] [PubMed] [Google Scholar]
  13. Jakobsson E., Moore L. E. On making models of the sodium inactivation of axonal membranes. Biophys J. 1971 Apr;11(4):385–386. doi: 10.1016/S0006-3495(71)86222-7. [DOI] [PMC free article] [PubMed] [Google Scholar]

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

RESOURCES