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. 1981 Feb;311:289–305. doi: 10.1113/jphysiol.1981.sp013585

Unitary current through sodium channel and anomalous rectifier channel estimated from transient current noise in the tunicate egg.

H Ohmori
PMCID: PMC1275410  PMID: 6267254

Abstract

1. The noise included in the Na current and the anomalous rectifier current was measured in intracellularly perfused eggs of Halocynthia roretzi Drashe under voltage clamp conditions. 2. The time-dependent component of the point-by-point ratio between the ensemble mean and the variance of successive current traces was the mirror image of the time-dependent component of the mean current itself. This can be explained by assuming an open or closed conductance state for each ionic channel, and permits estimation of unitary currents and channel number. 3. The unitary Na currents showed a potential dependence similar to that of the instantaneous currents. The unitary conductances (gamma) at zero membrane potential were 7.4 and 3.3 pmho in sea water with 400 and 100 mM-Na, respectively, and 400 mM-intracellular K. With 400 mM-Na intracellular perfusate and 400 mM-Na sea water, gamma was 15.7 pmho. In spite of the large differences in the unitary conductances, the single channel permeability for Na ions remained constant (1.15 x 10(-14) cm3 sec-1). The density of Na channels was 0.60/micrometer2. 4. The unitary currents calculated for the anomalous rectifier showed a potential dependence similar to that of the zero-time extrapolated estimates of the K inward currents. The anomalous rectifier unitary conductance was 5.5 and 6.9 pmho for sea water with 50 and 100 mM-K, respectively. The density of these channels was 0-035/micrometer2.

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Selected References

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  1. Anderson C. R., Stevens C. F. Voltage clamp analysis of acetylcholine produced end-plate current fluctuations at frog neuromuscular junction. J Physiol. 1973 Dec;235(3):655–691. doi: 10.1113/jphysiol.1973.sp010410. [DOI] [PMC free article] [PubMed] [Google Scholar]
  2. Conti F., De Felice L. J., Wanke E. Potassium and sodium ion current noise in the membrane of the squid giant axon. J Physiol. 1975 Jun;248(1):45–82. doi: 10.1113/jphysiol.1975.sp010962. [DOI] [PMC free article] [PubMed] [Google Scholar]
  3. Conti F., Hille B., Neumcke B., Nonner W., Stämpfli R. Conductance of the sodium channel in myelinated nerve fibres with modified sodium inactivation. J Physiol. 1976 Nov;262(3):729–742. doi: 10.1113/jphysiol.1976.sp011617. [DOI] [PMC free article] [PubMed] [Google Scholar]
  4. Conti F., Hille B., Neumcke B., Nonner W., Stämpfli R. Measurement of the conductance of the sodium channel from current fluctuations at the node of Ranvier. J Physiol. 1976 Nov;262(3):699–727. doi: 10.1113/jphysiol.1976.sp011616. [DOI] [PMC free article] [PubMed] [Google Scholar]
  5. 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]
  6. HODGKIN A. L., 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. doi: 10.1113/jphysiol.1949.sp004310. [DOI] [PMC free article] [PubMed] [Google Scholar]
  7. Hagiwara S., Yoshii M. Effects of internal potassium and sodium on the anomalous rectification of the starfish egg as examined by internal perfusion. J Physiol. 1979 Jul;292:251–265. doi: 10.1113/jphysiol.1979.sp012849. [DOI] [PMC free article] [PubMed] [Google Scholar]
  8. Katz B., Miledi R. The statistical nature of the acetycholine potential and its molecular components. J Physiol. 1972 Aug;224(3):665–699. doi: 10.1113/jphysiol.1972.sp009918. [DOI] [PMC free article] [PubMed] [Google Scholar]
  9. Keynes R. D., Ritchie J. M., Rojas E. The binding of tetrodotoxin to nerve membranes. J Physiol. 1971 Feb;213(1):235–254. doi: 10.1113/jphysiol.1971.sp009379. [DOI] [PMC free article] [PubMed] [Google Scholar]
  10. Keynes R. D., Rojas E. The temporal and steady-state relationships between activation of the sodium conductance and movement of the gating particles in the squid giant axon. J Physiol. 1976 Feb;255(1):157–189. doi: 10.1113/jphysiol.1976.sp011274. [DOI] [PMC free article] [PubMed] [Google Scholar]
  11. Levinson S. R., Meves H. The binding of tritiated tetrodotoxin to squid giant axons. Philos Trans R Soc Lond B Biol Sci. 1975 Jun 10;270(908):349–352. doi: 10.1098/rstb.1975.0014. [DOI] [PubMed] [Google Scholar]
  12. Moore J. W., Narahashi T., Shaw T. I. An upper limit to the number of sodium channels in nerve membrane? J Physiol. 1967 Jan;188(1):99–105. doi: 10.1113/jphysiol.1967.sp008126. [DOI] [PMC free article] [PubMed] [Google Scholar]
  13. Neher E., Stevens C. F. Conductance fluctuations and ionic pores in membranes. Annu Rev Biophys Bioeng. 1977;6:345–381. doi: 10.1146/annurev.bb.06.060177.002021. [DOI] [PubMed] [Google Scholar]
  14. Okamoto H., Takahashi K., Yoshii M. Membrane currents of the tunicate egg under the voltage-clamp condition. J Physiol. 1976 Jan;254(3):607–638. doi: 10.1113/jphysiol.1976.sp011249. [DOI] [PMC free article] [PubMed] [Google Scholar]
  15. Sigworth F. J. Sodium channels in nerve apparently have two conductance states. Nature. 1977 Nov 17;270(5634):265–267. doi: 10.1038/270265a0. [DOI] [PubMed] [Google Scholar]

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