Activity-dependent regulation of excitable axonal domains
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Rapid action potential propagation along myelinated axons requires voltage-gated Na+ channel clustering at the axon initial segments (AISs) and nodes of Ranvier. The AIS is intrinsically defined by cytoskeletal proteins expressed in axons, whereas nodes of Ranvier are formed by interaction between neurons and myelinating glia. These axonal domains have long been considered stable structures, but recent studies revealed that they are plastic and contribute to fine adjustment of neuronal activities and circuit function. The AIS changes its distribution and maintains neural circuit activity at a constant level. Morphological changes in myelinated nerve structures presumably modulate the excitability of nodal regions and regulate the timing of activity, thereby optimizing signal processing in a neural circuit. This review highlights recent findings on the structural plasticity of these excitable axonal domains.
KeywordsAxon initial segment Node of Ranvier Myelin Neuronal activity Plasticity Ion channel
The authors thank Dr. Debra A. Mayes (Department of Neuroscience, Cell Biology and Physiology, Wright State University, Dayton, OH) for meaningful discussions. This work was supported by grants-in-aid from MEXT (22680032 and 15H04257), the Uehara Memorial Foundation, and the JST PRESTO program to H.K.
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Conflict of interest
We declare no conflict of interest.