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. 1970 Dec;211(3):679–705. doi: 10.1113/jphysiol.1970.sp009299

Rate constants associated with changes in sodium conductance in axons perfused with sodium fluoride

W K Chandler, H Meves
PMCID: PMC1396074  PMID: 5501057

Abstract

1. Membrane currents during step depolarizations were measured in axons which were perfused with 300 mM-NaF and placed in K-free artificial sea-water, -0·3-4° C. The Na conductance was fitted by the modified Hodgkin—Huxley model, gNa = ḡNam3(h1 + h2). Changes in h1 and h2 were assumed to follow [Formula: see text] where x represents the inactive state.

2. The rate constants and steady-state values for m were in agreement with the Hodgkin—Huxley equations except that the experimental relationship of m∞3 against V was shifted 10-15 mV in the negative direction. This discrepancy, which was not found in an experiment with choline sea-water, can be explained on the basis of a resistance in series with the membrane between the voltage measuring electrodes.

3. At 0° C the rate constants (in msec-1) associated with changes in h1 and h2 were fitted using the following equations: βh1 = 0·5/{exp [- (V + 32)/10] + D1exp (- V/V1)}, αh2 = pexp (V/V2), βh2 = pexp (V/V2 - V/23·5) + pD2, with the condition that at 0 mV, (αh2 + βh2) = p(D2 + 2) = 0·55 msec-1. The experiments gave average values D1 = 3·6, V1 = 240 mV, p = 0·08 msec-1 and V2 = 70 mV. The average value of ḡNa was 66 mmho/cm2.

4. At negative voltages where m∞3 against V is steep, the points for βh1 and αh2/βh2 from axons in Na sea-water were not fitted well by the above equations whereas data from an axon in choline sea-water were. These discrepancies can be explained on the basis of a series resistance.

5. Measurements made at 16-17° C indicated that ḡNa has a Q10 of 1·6, τm-1 a Q10 of 2·8 and βh1 a Q10 of 3·5. The ratio αh2/βh2 was decreased relative to the value at 0° C and could be fitted by using Q10 = 0·6.

6. Measurements made with 250 mM-NaF + 50 mM-KF inside gave rate constants which were very similar to those obtained with 300 mM-NaF. Perfusion with 300 mM-KF appeared to double the value of βh1, relative to that obtained with 300 mM-NaF, and to reduce αh2/βh2 by about half.

7. The voltage dependence of αh2 makes it likely that following depolarization recovery from the inactive state x occurs via x → h1 rather than x → h2 → h1.

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Selected References

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

  1. BAKER P. F., HODGKIN A. L., MEVES H. THE EFFECT OF DILUTING THE INTERNAL SOLUTION ON THE ELECTRICAL PROPERTIES OF A PERFUSED GIANT AXON. J Physiol. 1964 Apr;170:541–560. doi: 10.1113/jphysiol.1964.sp007348. [DOI] [PMC free article] [PubMed] [Google Scholar]
  2. Chandler W. K., Hodgkin A. L. The effect of internal sodium on the action potential in the presence of different internal anions. J Physiol. 1965 Dec;181(3):594–611. doi: 10.1113/jphysiol.1965.sp007785. [DOI] [PMC free article] [PubMed] [Google Scholar]
  3. Chandler W. K., Meves H. Evidence for two types of sodium conductance in axons perfused with sodium fluoride solution. J Physiol. 1970 Dec;211(3):653–678. doi: 10.1113/jphysiol.1970.sp009298. [DOI] [PMC free article] [PubMed] [Google Scholar]
  4. Chandler W. K., Meves H. Slow changes in membrane permeability and long-lasting action potentials in axons perfused with fluoride solutions. J Physiol. 1970 Dec;211(3):707–728. doi: 10.1113/jphysiol.1970.sp009300. [DOI] [PMC free article] [PubMed] [Google Scholar]
  5. Chandler W. K., Meves H. Sodium and potassium currents in squid axons perfused with fluoride solutions. J Physiol. 1970 Dec;211(3):623–652. doi: 10.1113/jphysiol.1970.sp009297. [DOI] [PMC free article] [PubMed] [Google Scholar]
  6. FRANKENHAEUSER B., HODGKIN A. L. The action of calcium on the electrical properties of squid axons. J Physiol. 1957 Jul 11;137(2):218–244. doi: 10.1113/jphysiol.1957.sp005808. [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. 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]
  11. NARAHASHI T. DEPENDENCE OF RESTING AND ACTION POTENTIALS ON INTERNAL POTASSIUM IN PERFUSED SQUID GIANT AXONS. J Physiol. 1963 Nov;169:91–115. doi: 10.1113/jphysiol.1963.sp007243. [DOI] [PMC free article] [PubMed] [Google Scholar]
  12. TAYLOR R. E., MOORE J. W., COLE K. S. Analysis of certain errors in squid axon voltage clamp measurements. Biophys J. 1960 Nov;1:161–202. doi: 10.1016/s0006-3495(60)86882-8. [DOI] [PMC free article] [PubMed] [Google Scholar]

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