Slow mechanism for sodium permeability inactivation in myelinated nerve fibre of Xenopus laevis (original) (raw)

Abstract

1. Single myelinated nerve fibres were isolated and the nodal currents were recorded under potential clamp conditions. The effect of membrane potential on the Na permeability (PNa) mechanism was analysed. 2. The available PNa increased slowly during negative polarization of the membrane. The time course of this change was about 10(3) times slower than the time course of the mechanism for the usual PNa inactivation (h-system). The slow PNa changes could be distinguished from changes in h because of the difference in rate. 3. The slow PNa variation was independent of the state of the h-system and was largely due to a slow inactivation system, which empirically could be described as separate from the other permeability variables. 4. In the steady state the slow inactivation appeared almost absent at a holding potential of -120 mV, whereas it was 30% complete at the resting potential (-70 mV) and 80% complete at a holding potential of -20 mV. 5. Changes in the slow inactivation system showed an approximately exponential time course. At 10-12 degrees C the time constant was about 3 sec with U = -70 mV, 7 sec with U = -100 mV and 1-5 sec with U = -127 mV. 6. High Ca shifted the steady state slow inactivation curve in the positive direction along the potential axis.

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Selected References

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  1. Adelman W. J., Jr, Palti Y. The effects of external potassium and long duration voltage conditioning on the amplitude of sodium currents in the giant axon of the squid, Loligo pealei. J Gen Physiol. 1969 Nov;54(5):589–606. doi: 10.1085/jgp.54.5.589. [DOI] [PMC free article] [PubMed] [Google Scholar]
  2. Armstrong C. M., Bezanilla F., Rojas E. Destruction of sodium conductance inactivation in squid axons perfused with pronase. J Gen Physiol. 1973 Oct;62(4):375–391. doi: 10.1085/jgp.62.4.375. [DOI] [PMC free article] [PubMed] [Google Scholar]
  3. Bergman C. Increase of sodium concentration near the inner surface of the nodal membrane. Pflugers Arch. 1970;317(4):287–302. doi: 10.1007/BF00586578. [DOI] [PubMed] [Google Scholar]
  4. Brismar T., Frankenhaeuser B. Effects of ionic concentration on sodium permeability properties of myelinated nerve fibres of Xenopus laevis. J Physiol. 1975 Aug;249(3):549–559. doi: 10.1113/jphysiol.1975.sp011029. [DOI] [PMC free article] [PubMed] [Google Scholar]
  5. Brismar T., Frankenhaeuser B. The effect of calcium on the potassium permeability in the myelinated nerve fibre of Xenopus laevis. Acta Physiol Scand. 1972 Jun;85(2):237–241. doi: 10.1111/j.1748-1716.1972.tb05256.x. [DOI] [PubMed] [Google Scholar]
  6. Brismar T. Processes for sodium permeability inactivation in the myelinated nerve fibre of the frog (Xenopus laevis). Acta Physiol Scand. 1976 Jun;97(2):258–260. doi: 10.1111/j.1748-1716.1976.tb10259.x. [DOI] [PubMed] [Google Scholar]
  7. 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]
  8. DODGE F. A., FRANKENHAEUSER B. Membrane currents in isolated frog nerve fibre under voltage clamp conditions. J Physiol. 1958 Aug 29;143(1):76–90. doi: 10.1113/jphysiol.1958.sp006045. [DOI] [PMC free article] [PubMed] [Google Scholar]
  9. Drouin H., Neumcke B. Specific and unspecific charges at the sodium channels of the nerve membrane. Pflugers Arch. 1974;351(3):207–229. doi: 10.1007/BF00586919. [DOI] [PubMed] [Google Scholar]
  10. FRANKENHAEUSER B., HUXLEY A. F. THE ACTION POTENTIAL IN THE MYELINATED NERVE FIBER OF XENOPUS LAEVIS AS COMPUTED ON THE BASIS OF VOLTAGE CLAMP DATA. J Physiol. 1964 Jun;171:302–315. doi: 10.1113/jphysiol.1964.sp007378. [DOI] [PMC free article] [PubMed] [Google Scholar]
  11. FRANKENHAEUSER B. INACTIVATION OF THE SODIUM-CARRYING MECHANISM IN MYELINATED NERVE FIBRES OF XENOPUS LAEVIS. J Physiol. 1963 Nov;169:445–451. doi: 10.1113/jphysiol.1963.sp007271. [DOI] [PMC free article] [PubMed] [Google Scholar]
  12. FRANKENHAEUSER B. Quantitative description of sodium currents in myelinated nerve fibres of Xenopus laevis. J Physiol. 1960 Jun;151:491–501. doi: 10.1113/jphysiol.1960.sp006455. [DOI] [PMC free article] [PubMed] [Google Scholar]
  13. FRANKENHAEUSER B. Steady state inactivation of sodium permeability in myelinated nerve fibres of Xenopus laevis. J Physiol. 1959 Oct;148:671–676. doi: 10.1113/jphysiol.1959.sp006316. [DOI] [PMC free article] [PubMed] [Google Scholar]
  14. FRANKENHAEUSER B., VALLBO A. B. ACCOMMODATION IN MYELINATED NERVE FIBRES OF XENOPUS LAEVIS AS COMPUTED ON THE BASIS OF VOLTAGE CLAMP DATA. Acta Physiol Scand. 1965 Jan-Feb;63:1–20. doi: 10.1111/j.1748-1716.1965.tb04037.x. [DOI] [PubMed] [Google Scholar]
  15. Fox J. M. Ultra-slow inactivation of the ionic currents through the membrane of myelinated nerve. Biochim Biophys Acta. 1976 Mar 5;426(2):232–244. doi: 10.1016/0005-2736(76)90334-5. [DOI] [PubMed] [Google Scholar]
  16. Frankenhaeuser B., Arhem P. Steady state current rectification in potential clamped nodes of Ranvier (Xenopus laevis). Philos Trans R Soc Lond B Biol Sci. 1975 Jun 10;270(908):515–525. doi: 10.1098/rstb.1975.0028. [DOI] [PubMed] [Google Scholar]
  17. 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]
  18. Neumcke B., Fox J. M., Drouin H., Schwarz W. Kinetics of the slow variation of peak sodium current in the membrane of myelinated nerve following changes of holding potential or extracellular pH. Biochim Biophys Acta. 1976 Mar 5;426(2):245–257. doi: 10.1016/0005-2736(76)90335-7. [DOI] [PubMed] [Google Scholar]
  19. Schauf C. L., Pencek T. L., Davis F. A. Slow sodium inactivation in Myxicola axons. Evidence for a second inactive state. Biophys J. 1976 Jul;16(7):771–778. doi: 10.1016/S0006-3495(76)85727-X. [DOI] [PMC free article] [PubMed] [Google Scholar]
  20. VALLBO A. B. ACCOMMODATION RELATED TO INACTIVATION OF THE SODIUM PERMEABILITY IN SINGLE MYELINATED NERVE FIBRES FROM XENOPUS LAEVIS. Acta Physiol Scand. 1964 Aug;61:429–444. [PubMed] [Google Scholar]