Neurology
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Although neurophysiologic doctrine has traditionally referred to "the" voltage-gated sodium channel, it is now clear that there are at least nine genes that encode molecularly and physiologically distinct sodium channels. Mutations of sodium channel genes provide a basis for genetic channelopathies. Dysregulated expression of sodium channels due to alterations in activity of nonmutated channel genes, on the other hand, can produce acquired channelopathies. ⋯ Emerging evidence also suggests that an acquired channelopathy, characterized by abnormal expression of sensory neuron specific sodium channels that can alter impulse trafficking within Purkinje cells, may contribute to the pathophysiology of MS. Subtype-specific drugs that selectively modulate various types of channels probably will soon be developed. The acquired channelopathies associated with nerve injury and MS may thus represent prototype disorders that present therapeutic opportunities.