HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Kostyuk, P. G. Articles by Shakhovalov, Y. A. Search for Related Content PubMed PubMed Citation Articles by Kostyuk, P. G. Articles by Shakhovalov, Y. A.

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 (K_d = 7·2 x 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/_ns). 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 V_m = 0 are: _m(Na) = 1·1 ± 0·5 msec, _m(Ca) = 2·4 ± 1·0 msec, _h(Na) = 7·9 ± 2·0 msec. The inactivation of Ca current included two first-order kinetic processes with _h1 = 50 ± 10 msec and _h = 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.

This article has been cited by other articles:

				R. Berra-Romani, M. P. Blaustein, and D. R. Matteson TTX-sensitive voltage-gated Na+ channels are expressed in mesenteric artery smooth muscle cells Am J Physiol Heart Circ Physiol, July 1, 2005; 289(1): H137 - H145. [Abstract] [Full Text] [PDF]

				T. E. Decoursey Voltage-Gated Proton Channels and Other Proton Transfer Pathways Physiol Rev, April 1, 2003; 83(2): 475 - 579. [Abstract] [Full Text] [PDF]

				Y.-H. Zhang, J. L. Kenyon, and G. D. Nicol Phorbol Ester-Induced Inhibition of Potassium Currents in Rat Sensory Neurons Requires Voltage-Dependent Entry of Calcium J Neurophysiol, January 1, 2001; 85(1): 362 - 373. [Abstract] [Full Text] [PDF]

				W. F. Gilly, R. Gillette, and M. McFarlane Fast and Slow Activation Kinetics of Voltage-Gated Sodium Channels in Molluscan Neurons J Neurophysiol, May 1, 1997; 77(5): 2373 - 2384. [Abstract] [Full Text] [PDF]