Abstract
The sodium flux ratio across the axolemma of internally perfused, voltage-clamped giant axons of Loligo pealei has been measured at various membrane potentials. The flux ratio exponent obtained from these measurements was about unity and independent of membrane voltage over the 50 mV range from about -20 to l mV. These results, combined with previous measurements of ion permeation through sodium channels, show that the sodium channel behaves like a multi-ion pore with two ion binding sites that are rarely simultaneously occupied by sodium.
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Selected References
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- 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]
- Armstrong C. M. Potassium pores of nerve and muscle membranes. Membranes. 1975;3:325–358. [PubMed] [Google Scholar]
- Begenisich T. B., Cahalan M. D. Sodium channel permeation in squid axons. II: Non-independence and current-voltage relations. J Physiol. 1980 Oct;307:243–257. doi: 10.1113/jphysiol.1980.sp013433. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Begenisich T., De Weer P. Ionic interactions in the potassium channel of squid giant axons. Nature. 1977 Oct 20;269(5630):710–711. doi: 10.1038/269710a0. [DOI] [PubMed] [Google Scholar]
- Begenisich T., De Weer P. Potassium flux ratio in voltage-clamped squid giant axons. J Gen Physiol. 1980 Jul;76(1):83–98. doi: 10.1085/jgp.76.1.83. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Begenisich T., Lynch C. Effects of internal divalent cations on voltage-clamped squid axons. J Gen Physiol. 1974 Jun;63(6):675–689. doi: 10.1085/jgp.63.6.675. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Cahalan M., Begenisich T. Sodium channel selectivity. Dependence on internal permeant ion concentration. J Gen Physiol. 1976 Aug;68(2):111–125. doi: 10.1085/jgp.68.2.111. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 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]
- HODGKIN A. L., KEYNES R. D. The potassium permeability of a giant nerve fibre. J Physiol. 1955 Apr 28;128(1):61–88. doi: 10.1113/jphysiol.1955.sp005291. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Heckmann K. Single file diffusion. Biomembranes. 1972;3:127–153. doi: 10.1007/978-1-4684-0961-1_9. [DOI] [PubMed] [Google Scholar]
- Hille B. Ionic selectivity, saturation, and block in sodium channels. A four-barrier model. J Gen Physiol. 1975 Nov;66(5):535–560. doi: 10.1085/jgp.66.5.535. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Hille B., Schwarz W. K channels in excitable cells as multi-ion pores. Brain Res Bull. 1979 Jan-Feb;4(1):159–162. doi: 10.1016/0361-9230(79)90079-0. [DOI] [PubMed] [Google Scholar]
- Hille B., Schwarz W. Potassium channels as multi-ion single-file pores. J Gen Physiol. 1978 Oct;72(4):409–442. doi: 10.1085/jgp.72.4.409. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Hladky S. B., Harris J. D. An ion displacement membrame model. Biophys J. 1967 Sep;7(5):535–543. doi: 10.1016/s0006-3495(67)86604-9. [DOI] [PMC free article] [PubMed] [Google Scholar]
- MULLINS L. J., ADELMAN W. J., Jr, SJODIN R. A. Sodium and potassium ion effluxes from squid axons under voltage clamp conditions. Biophys J. 1962 May;2:257–274. doi: 10.1016/s0006-3495(62)86854-4. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Mozhayeva G. N., Naumov A. P., Negulyaev Y. A., Nosyreva E. D. The permeability of aconitine-modified sodium channels to univalent cations in myelinated nerve. Biochim Biophys Acta. 1977 May 2;466(3):461–473. doi: 10.1016/0005-2736(77)90339-x. [DOI] [PubMed] [Google Scholar]
- Rudy B. Slow inactivation of the sodium conductance in squid giant axons. Pronase resistance. J Physiol. 1978 Oct;283:1–21. doi: 10.1113/jphysiol.1978.sp012485. [DOI] [PMC free article] [PubMed] [Google Scholar]