Immunolocalisation of sodium channel NaG in the intact and injured human peripheral nervous system

The voltage-gated 'glial' sodium channel NaG belongs to a distinct molecula r class within the multi-gene family of mammalian sodium channels. Original ly found in central and peripheral glia, NaG has since been detected in neu rons in rat dorsal root ganglia (DRG) and may play a role in Schwann cell-a xon interactions. We have studied the presence of NaG-like immunoreactivity in the intact and injured human peripheral nervous system using a specific affinity-purified antibody. Nerve fibres in normal and injured peripheral nerves and normal skin exhibited intense NaG-immunoreactivity. Numerous NaG -immunoreactive nerve fibres surrounded neuronal cell bodies within postmor tem control DRG, and in DRG avulsed from the spinal cord (i.e. after trauma tic central axotomy). There were no significant differences in the pattern of NaG immunostaining between control and avulsed DRG, or with delay after injury. Generally, the neuronal cell bodies were only very weakly immunorea ctive to NaG, indicating that the NaG immunoreactivity was predominantly in Schwann cells/myelin. In accord, we demonstrated NaG immunostaining in cul tured human and rat Schwann cells, and in distal nerve after wallerian dege neration. NaG thus appears to be a useful new marker for Schwann cells in t he human PNS, and a role in neuropathy deserves investigation.