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. 1977 Sep;270(3):545–568. doi: 10.1113/jphysiol.1977.sp011968

Separation of sodium and calcium currents in the somatic membrane of mollusc neurones. With an Appendix by Yu A. Shakhovalov

P G Kostyuk, O A Krishtal, Yu A Shakhovalov
PMCID: PMC1353531  PMID: 903906

Abstract

1. Characteristics of the transmembrane ionic currents under controlled changes in ionic composition of extra- and intracellular medium were studied in isolated neurones from the ganglia of molluscs, Helix pomatia, Limnea stagnalis and Planorbis corneus. The neurones were investigated by a new technique which allows for dialysis of their interior and for clamping of the potential at the surface membrane without using micro-electrodes.

2. Replacement of K ions by Tris inside the neurones eliminated the outward K current so that the actual time course of the inward current could be measured. The latter was separated into two additive components, one of which was carried by Na ions and the other one by Ca ions.

3. Both inward currents were unaltered by tetrodotoxin (TTX); however, Ca current could be separately blocked by externally applied Cd ions (Kd = 7·2 × 10-5 M) and by the use of fluoride as an intracellular anion.

4. No reversal of Na inward current could be achieved in neurones dialysed with Na-free solution, indicating the absence of outward current carrying ions through the corresponding channels. With 5 mM-Na inside the cell, the equilibrium potential was close to the value predicted by the Nernst equilibrium.

5. A non-specific outward current could be detected in K-free cells at membrane potentials exceeding 20-40 mV. Its time course was proportional to 1 — exp (—t/τns). Cd ions depressed this current. The presence of the non-specific outward current made an exact measurement of the equilibrium potential for the Ca inward current impossible.

6. The kinetics of Na inward currents could be described by m3h and those of the Ca current by m2h law. The corresponding values for Vm = 0 are: τm(Na) = 1·1 ± 0·5 msec, τm(Ca) = 2·4 ± 1·0 msec, τh(Na) = 7·9 ± 2·0 msec. The inactivation of Ca current included two first-order kinetic processes with τh1 = 50 ± 10 msec and τh = 320 ± 30 msec.

7. The data presented are considered to be a proof of the existence of separate systems of Na and Ca ion-conducting channels in the nerve cell membrane.

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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., Ridgway E. B. Depolarization and calcium entry in squid giant axons. J Physiol. 1971 Nov;218(3):709–755. doi: 10.1113/jphysiol.1971.sp009641. [DOI] [PMC free article] [PubMed] [Google Scholar]
  2. Baker P. F., Meves H., Ridgway E. B. Calcium entry in response to maintained depolarization of squid axons. J Physiol. 1973 Jun;231(3):527–548. doi: 10.1113/jphysiol.1973.sp010247. [DOI] [PMC free article] [PubMed] [Google Scholar]
  3. Doroshenko P. A., Kostiuk P. G., Kryshtal' O. A. Deistvie kal'tsiia na membranu somy gigantskikh neironov molliuskov. Neirofiziologiia. 1973 Nov-Dec;5(6):621–627. [PubMed] [Google Scholar]
  4. Eckert R., Lux H. D. A non-inactivating inward current recorded during small depolarizing voltage steps in snail pacemaker neurons. Brain Res. 1975 Jan 17;83(3):486–489. doi: 10.1016/0006-8993(75)90840-9. [DOI] [PubMed] [Google Scholar]
  5. Eckert R., Lux H. D. A voltage-sensitive persistent calcium conductance in neuronal somata of Helix. J Physiol. 1976 Jan;254(1):129–151. doi: 10.1113/jphysiol.1976.sp011225. [DOI] [PMC free article] [PubMed] [Google Scholar]
  6. Geduldig D., Gruener R. Voltage clamp of the Aplysia giant neurone: early sodium and calcium currents. J Physiol. 1970 Nov;211(1):217–244. doi: 10.1113/jphysiol.1970.sp009276. [DOI] [PMC free article] [PubMed] [Google Scholar]
  7. Geduldig D., Junge D. Sodium and calcium components of action potentials in the Aplysia giant neurone. J Physiol. 1968 Dec;199(2):347–365. doi: 10.1113/jphysiol.1968.sp008657. [DOI] [PMC free article] [PubMed] [Google Scholar]
  8. Gola M. Neurones à ondes-salves des mollusques. Variations cycliques lentes des conductances ioniques. Pflugers Arch. 1974;352(1):17–36. doi: 10.1007/BF01061947. [DOI] [PubMed] [Google Scholar]
  9. 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]
  10. Hagiwara S., Fukuda J., Eaton D. C. Membrane currents carried by Ca, Sr, and Ba in barnacle muscle fiber during voltage clamp. J Gen Physiol. 1974 May;63(5):564–578. doi: 10.1085/jgp.63.5.564. [DOI] [PMC free article] [PubMed] [Google Scholar]
  11. Katz B., Miledi R. The timing of calcium action during neuromuscular transmission. J Physiol. 1967 Apr;189(3):535–544. doi: 10.1113/jphysiol.1967.sp008183. [DOI] [PMC free article] [PubMed] [Google Scholar]
  12. Keynes R. D., Rojas E., Taylor R. E., Vergara J. Calcium and potassium systems of a giant barnacle muscle fibre under membrane potential control. J Physiol. 1973 Mar;229(2):409–455. doi: 10.1113/jphysiol.1973.sp010146. [DOI] [PMC free article] [PubMed] [Google Scholar]
  13. Kohlhardt M., Bauer B., Krause H., Fleckenstein A. Differentiation of the transmembrane Na and Ca channels in mammalian cardiac fibres by the use of specific inhibitors. Pflugers Arch. 1972;335(4):309–322. doi: 10.1007/BF00586221. [DOI] [PubMed] [Google Scholar]
  14. Kostyuk P. G., Krishtal O. A., Doroshenko P. A. Calcium currents in snail neurones. I. Identification of calcium current. Pflugers Arch. 1974 Apr 11;348(2):83–93. doi: 10.1007/BF00586471. [DOI] [PubMed] [Google Scholar]
  15. Kostyuk P. G., Krishtal O. A., Doroshenko P. A. Calcium currents in snail neurones. II. The effect of external calcium concentration on the calcium inward current. Pflugers Arch. 1974 Apr 11;348(2):95–104. doi: 10.1007/BF00586472. [DOI] [PubMed] [Google Scholar]
  16. Kostyuk P. G., Krishtal O. A., Pidoplichko V. I. Effect of internal fluoride and phosphate on membrane currents during intracellular dialysis of nerve cells. Nature. 1975 Oct 23;257(5528):691–693. doi: 10.1038/257691a0. [DOI] [PubMed] [Google Scholar]
  17. Kryshtal' O. A., Pidoplichko V. I. Vnutrikletochnaia perfuziia gigantskikh neironov ulitki. Neirofiziologiia. 1975;7(3):327–329. [PubMed] [Google Scholar]
  18. Lux H. D., Eckert R. Inferred slow inward current in snail neurones. Nature. 1974 Aug 16;250(467):574–576. doi: 10.1038/250574a0. [DOI] [PubMed] [Google Scholar]
  19. Meves H., Vogel W. Calcium inward currents in internally perfused giant axons. J Physiol. 1973 Nov;235(1):225–265. doi: 10.1113/jphysiol.1973.sp010386. [DOI] [PMC free article] [PubMed] [Google Scholar]
  20. New W., Trautwein W. The ionic nature of slow inward current and its relation to contraction. Pflugers Arch. 1972;334(1):24–38. doi: 10.1007/BF00585998. [DOI] [PubMed] [Google Scholar]
  21. Standen N. B. Voltage-clamp studies of the calcium inward current in an identified snail neurone: comparison with the sodium inward current. J Physiol. 1975 Jul;249(2):253–268. doi: 10.1113/jphysiol.1975.sp011014. [DOI] [PMC free article] [PubMed] [Google Scholar]
  22. Tarr M. Two inward currents in frog atrial muscle. J Gen Physiol. 1971 Nov;58(5):523–543. doi: 10.1085/jgp.58.5.523. [DOI] [PMC free article] [PubMed] [Google Scholar]
  23. Washio H. Calcium inward currents in insect muscle fibers. Can J Physiol Pharmacol. 1972 Nov;50(11):1114–1116. doi: 10.1139/y72-163. [DOI] [PubMed] [Google Scholar]

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