CHAPEL HILL, N.C. -- New research from the University of North Carolina at Chapel Hill School of Medicine describes a key molecular mechanism in nerve fibers that ensures the rapid conductance of nervous system impulses. The findings appear online Jan. 27, 2011 in the journal Neuron.
Our hard-wired nerve fibers or axons rely on an insulating membrane sheath, the myelin, made up of fatty white matter to accelerate the rate of transmission of electrical impulses from the brain to other parts of the body.
Myelin thus acts to prevent electrical current from leaking or prematurely leaving the axon. However, the myelin surrounding the axon isn't continuous; there are regularly spaced unmyelinated gaps about 1 micrometer wide along the axon. These unmyelinated regions named as nodes of Ranvier are where electrical impulses hop from one node to the next along the axon, at rates as fast as 160 meters per second (360 mph).
Determining exactly how the nodes of Ranvier function and how they are assembled, has fired the interest of neuroscientists for more than a century," said UNC neuroscientist Manzoor Bhat, PhD, Professor of Cell and Molecular Physiology in the UNC Neuroscience Research Center. "The answers may also provide important clues to the development of targeted treatments for multiple sclerosis and other disorders involving demyelination and/or disorganization of nodes of Ranvier."
Bhat and colleagues focused on a protein called Neurofascin 186, which accumulates in the membranes of axons at the nodes of Ranvier. Together with proteins Ankyrin-G and sodium channels, these molecules form a complex that facilitates passage of sodium ions through the channels in axons, thus making them paramount for the propagation of nerve impulses along myelinated nerve fibers.
Bhat's team had previously identified a homolog of Neurofascin in laboratory studies of Drosophila nerve fibers, and because its in vivo function had n
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University of North Carolina School of Medicine