| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
We investigated voltage-gated potassium channels in human peripheral myelinated axons; apart from the I, S and F channels already described in amphibian and rat axons, we identified at least two other channel types.
The I channel activated between -70 and -40 mV, and inactivated very slowly (time constant 13·1 s at -40 mV). It had two gating modes: the dominant ('noisy') mode had a conductance of 30 pS (inward current, symmetrical 155 mM K+) and a deactivation time constant (
) of 25 ms (-80 mV); it accounted for most (~50-75 %) of the macroscopic K+ current in large patches. The secondary ('flickery') gating mode had a conductance of 22 pS, and showed bi-exponential deactivation ( = 16 and 102 ms; -80 mV); it contributed part of the slow macroscopic K+ current.
The I channel current was blocked by 1 µM 
-dendrotoxin (DTX); we also observed two other DTX-sensitive K+ channel types (40 pS and 25 pS). The S and F channels were not blocked by 1 µM DTX.
The conductance of the S channel was 7-10 pS, and it activated at slightly more negative potentials than the I channel; its deactivation was slow ( = 41·7 ms at -100 mV). It contributed a second component of the slow macroscopic K+ current.
The F channel had a conductance of 50 pS; it activated at potentials between -40 and +40 mV, deactivated very rapidly ( = 1·4 ms at -100 mV), and inactivated rapidly ( = 62 ms at +80 mV). It accounted for the fast-deactivating macroscopic K+ current and partly for fast K+ current inactivation.
We conclude that human and rat axonal K+ channels are closely similar, but that the correspondence between K+ channel types and the macroscopic currents usually attributed to them is only partial. At least five channel types exist, and their characteristics overlap to a considerable extent.
This article has been cited by other articles:
|
|
 |
|
  K. A. Kleopa, L. B. Elman, B. Lang, A. Vincent, and S. S. Scherer Neuromyotonia and limbic encephalitis sera target mature Shaker-type K+ channels: subunit specificity correlates with clinical manifestations Brain, June 1, 2006; 129(6): 1570 - 1584. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 J. R. Schwarz, G. Glassmeier, E. C. Cooper, T.-C Kao, H. Nodera, D. Tabuena, R. Kaji, and H. Bostock KCNQ channels mediate IKs, a slow K+ current regulating excitability in the rat node of Ranvier J. Physiol., May 15, 2006; 573(1): 17 - 34. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 J. Devaux, G. Alcaraz, J. Grinspan, V. Bennett, R. Joho, M. Crest, and S. S. Scherer Kv3.1b Is a Novel Component of CNS Nodes J. Neurosci., June 1, 2003; 23(11): 4509 - 4518. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 J. Devaux, M. Gola, G. Jacquet, and M. Crest Effects of K+ Channel Blockers on Developing Rat Myelinated CNS Axons: Identification of Four Types of K+ Channels J Neurophysiol, March 1, 2002; 87(3): 1376 - 1385. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
C. C. McIntyre, A. G. Richardson, and W. M. Grill Modeling the Excitability of Mammalian Nerve Fibers: Influence of Afterpotentials on the Recovery Cycle J Neurophysiol, February 1, 2002; 87(2): 995 - 1006. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
R. Bal and D. Oertel Potassium Currents in Octopus Cells of the Mammalian Cochlear Nucleus J Neurophysiol, November 1, 2001; 86(5): 2299 - 2311. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
C. Chabbert, J. M. Chambard, A. Sans, and G. Desmadryl Three Types of Depolarization-Activated Potassium Currents in Acutely Isolated Mouse Vestibular Neurons J Neurophysiol, March 1, 2001; 85(3): 1017 - 1026. [Abstract] [Full Text] [PDF]
|
|
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
