title: Specific permeability properties of demyelinated rat nerve fibres.
abstract: The specific permeability properties of isolated rat fibres with diphtheria toxin induced paranodal demyelination were investigated in potential clamp experiments. Nodal widening (4 to 6 micrometers) and paranodal demyelination (20 to 90 micrometers) were associated with a very large increase in the normally low delayed K-permeability (greater than 10 times). The resting K-permeability (which was comparatively large in the rat fibres) was similarly increased, which decreased action potential amplitude and excitability. Fibres with paranodal demyelination had, in addition, a large increase in the maximum peak Na-permeability (2 to 5 times the normal), which indicated that excitability was upheld by formation of new Na-permeability sites. The conduction defects in demyelinated fibres can therefore not be related to the size of the demyelination, but to the specific permeability changes in the demyelinated segment.
mesh_terms: D000200:Action Potentials; D000818:Animals; D002463:Cell Membrane Permeability; D003711:Demyelinating Diseases / Q000139:chemically induced; D004167:Diphtheria Toxin; D004558:Electric Stimulation; D008564:Membrane Potentials; D009413:Nerve Fibers, Myelinated / Q000502:physiology*; D009431:Neural Conduction; D011188:Potassium / Q000378:metabolism*; D051381:Rats; D012584:Sciatic Nerve / Q000187:drug effects; D012964:Sodium / Q000378:metabolism*
chemical_list: D004167:Diphtheria Toxin; D012964:Sodium; D011188:Potassium