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


Author(s): Jonas, Peter; Bräu, Michael E; Hermsteiner, Markus; Vogel, Werner
Article Title: Single-channel recording in myelinated nerve fibers reveals one type of Na channel but different K channels
Affiliation
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.
Keywords: Animals; Kinetics; Axons/physiology; Sodium Channels/physiology; Xenopus laevis; Membrane Potentials; Axons/ultrastructure; Nerve Fibers, Myelinated/physiology; Potassium Channels/physiology; Sciatic Nerve/physiology
Journal Title: PNAS
Volume: 86
Issue 18
ISSN: 1091-6490
Publisher: National Academy of Sciences  
Date Published: 1989-09-01
Start Page: 7238
End Page: 7242
URL:
Open access: no