Skip to main content
NCBI home page
Proceedings of the National Academy of Sciences of the United States of America logoLink to Proceedings of the National Academy of Sciences of the United States of America
. 1989 Sep;86(18):7238–7242. doi: 10.1073/pnas.86.18.7238

Single-channel recording in myelinated nerve fibers reveals one type of Na channel but different K channels.

P Jonas 1, M E Bräu 1, M Hermsteiner 1, W Vogel 1
PMCID: PMC298032  PMID: 2550937

Abstract

Amphibian myelinated nerve fibers were treated with collagenase and protease. Axons with retraction of the myelin sheath were patch-clamped in the nodal and paranodal region. One type of Na channel was found. It has a single-channel conductance of 11 pS (15 degrees C) and is blocked by tetrodotoxin. Averaged events show the typical activation and inactivation kinetics of macroscopic Na current. Three potential-dependent K channels were identified (I, F, and S channel). The I channel, being the most frequent type, has a single-channel conductance of 23 pS (inward current, 105 mM K on both sides of the membrane), activates between -60 and -30 mV, deactivates with intermediate kinetics, and is sensitive to dendrotoxin. The F channel has a conductance of 30 pS, activates between -40 and 60 mV, and deactivates with fast kinetics. The former inactivates within tens of seconds; the latter inactivates within seconds. The third type, the S channel, has a conductance of 7 pS and deactivates slowly. All three channels can be blocked by external tetraethylammonium chloride. We suggest that these distinct K channel types form the basis for the different components of macroscopic K current described previously.

Full text

PDF
7238

Images in this article

7239Image
on p.7239

Selected References

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

  1. Benoit E., Dubois J. M. Toxin I from the snake Dendroaspis polylepis polylepis: a highly specific blocker of one type of potassium channel in myelinated nerve fiber. Brain Res. 1986 Jul 9;377(2):374–377. doi: 10.1016/0006-8993(86)90884-x. [DOI] [PubMed] [Google Scholar]
  2. Berthold C. H., Rydmark M. Electrophysiology and morphology of myelinated nerve fibers. VI. Anatomy of the paranode-node-paranode region in the cat. Experientia. 1983 Sep 15;39(9):964–976. doi: 10.1007/BF01989761. [DOI] [PubMed] [Google Scholar]
  3. Bezanilla F. Single sodium channels from the squid giant axon. Biophys J. 1987 Dec;52(6):1087–1090. doi: 10.1016/S0006-3495(87)83304-0. [DOI] [PMC free article] [PubMed] [Google Scholar]
  4. Chiu S. Y., Ritchie J. M. Evidence for the presence of potassium channels in the paranodal region of acutely demyelinated mammalian single nerve fibres. J Physiol. 1981;313:415–437. doi: 10.1113/jphysiol.1981.sp013674. [DOI] [PMC free article] [PubMed] [Google Scholar]
  5. 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]
  6. Conti F., Hille B., Nonner W. Non-stationary fluctuations of the potassium conductance at the node of ranvier of the frog. J Physiol. 1984 Aug;353:199–230. doi: 10.1113/jphysiol.1984.sp015332. [DOI] [PMC free article] [PubMed] [Google Scholar]
  7. Dubois J. M. Evidence for the existence of three types of potassium channels in the frog Ranvier node membrane. J Physiol. 1981 Sep;318:297–316. doi: 10.1113/jphysiol.1981.sp013865. [DOI] [PMC free article] [PubMed] [Google Scholar]
  8. Dubois J. M. Simultaneous changes in the equilibrium potential and potassium conductance in voltage clamped Ranvier node in the frog. J Physiol. 1981 Sep;318:279–295. doi: 10.1113/jphysiol.1981.sp013864. [DOI] [PMC free article] [PubMed] [Google Scholar]
  9. Grissmer S. Properties of potassium and sodium channels in frog internode. J Physiol. 1986 Dec;381:119–134. doi: 10.1113/jphysiol.1986.sp016317. [DOI] [PMC free article] [PubMed] [Google Scholar]
  10. Hamill O. P., Marty A., Neher E., Sakmann B., Sigworth F. J. Improved patch-clamp techniques for high-resolution current recording from cells and cell-free membrane patches. Pflugers Arch. 1981 Aug;391(2):85–100. doi: 10.1007/BF00656997. [DOI] [PubMed] [Google Scholar]
  11. Marty A. Blocking of large unitary calcium-dependent potassium currents by internal sodium ions. Pflugers Arch. 1983 Feb;396(2):179–181. doi: 10.1007/BF00615524. [DOI] [PubMed] [Google Scholar]
  12. Neumcke B., Schwarz W., Stämpfli R. Differences between K channels in motor and sensory nerve fibres of the frog as revealed by fluctuation analysis. Pflugers Arch. 1980 Aug;387(1):9–16. doi: 10.1007/BF00580838. [DOI] [PubMed] [Google Scholar]
  13. Schwarz J. R., Vogel W. Potassium inactivation in single myelinated nerve fibres of Xenopus laevis. Pflugers Arch. 1971;330(1):61–73. doi: 10.1007/BF00588735. [DOI] [PubMed] [Google Scholar]
  14. Shrager P. The distribution of sodium and potassium channels in single demyelinated axons of the frog. J Physiol. 1987 Nov;392:587–602. doi: 10.1113/jphysiol.1987.sp016798. [DOI] [PMC free article] [PubMed] [Google Scholar]
  15. Sigworth F. J. The variance of sodium current fluctuations at the node of Ranvier. J Physiol. 1980 Oct;307:97–129. doi: 10.1113/jphysiol.1980.sp013426. [DOI] [PMC free article] [PubMed] [Google Scholar]
  16. Stühmer W., Stocker M., Sakmann B., Seeburg P., Baumann A., Grupe A., Pongs O. Potassium channels expressed from rat brain cDNA have delayed rectifier properties. FEBS Lett. 1988 Dec 19;242(1):199–206. doi: 10.1016/0014-5793(88)81015-9. [DOI] [PubMed] [Google Scholar]

Articles from Proceedings of the National Academy of Sciences of the United States of America are provided here courtesy of National Academy of Sciences

RESOURCES