title: Permeability of the paranodal junction of myelinated nerve fibers.
abstract: We have used fluorescent dextran tracers to test the tightness of the paranodal junction of living or fixed myelinated fibers in mouse sciatic nerve. Both 3 and 70 kDa tracers are able to penetrate from the perinodal space symmetrically into the paranodes on either side of the node of Ranvier at a rate consistent with diffusion through an elongated helical pathway between the paranodal terminal loops of the myelin sheath. This pathway thus provides an access route for movement of water soluble nutrients and metabolites to and from the internodal axon and constitutes a pathway through which juxtaparanodal potassium channels may be activated and may in turn affect nodal excitability. This pathway may also allow access of antibodies and toxic molecules to the internodal axon in paraneoplastic syndromes and demyelinating diseases.
authors.affiliation: Department of Physiology and Neuroscience and Rusk Institute, New York University School of Medicine, New York, NY 10016, USA.
authors.forename: Amanda
authors.initials: A
authors.lastname: Mierzwa
authors.forename: Seema
authors.initials: S
authors.lastname: Shroff
authors.forename: Jack
authors.initials: J
authors.lastname: Rosenbluth
mesh_terms: D000818:Animals; D002463:Cell Membrane Permeability / Q000502:physiology; D005260:Female; D008297:Male; D051379:Mice; D009413:Nerve Fibers, Myelinated / Q000378:metabolism* / Q000648:ultrastructure; D011849:Radioactive Tracers; D011901:Ranvier's Nodes / Q000378:metabolism* / Q000648:ultrastructure; D012584:Sciatic Nerve / Q000378:metabolism / Q000648:ultrastructure
chemical_list: D011849:Radioactive Tracers