Sodium channels accumulate at the tips of injured axons

The axolemmal distribution of voltage-gated sodium channels largely determines the regions of axonal electrical excitability. Using a well-characterized anti-sodium channel antibody, we examined peripheral nerve fibers focally injured by exposure to the neurotoxic agent, potassium tellurite (K2TeO3). Immunocytochemical and radioimmunoassay data showed a focal accumulation of sodium channels within the tips of injured axons. The major increase in sodium channel concentration occurred between 7 and 11 days after toxin exposure; however, immunocytochemically, excess sodium channels persisted in several axonal endings for a much longer time. The accumulation of sodium channels at injured axonal tips may be responsible, in part, for ectopic axonal excitability and the resulting abnormal sensory phenomena (especially pain and paresthesias) which frequently complicate peripheral nerve injury in humans.