Impaired Ranvier node sodium-potassium adenosine triphosphatase may induce facial palsy

To clarify the part of the neuron essential for myelinated nerve conduction, the cytochemical localization of potassium ion (K+)-dependent p-nitrophenylphosphatase (K-NPPase) activity was investigated in the normal and reserpine-treated facial nerve of guinea pigs. In the normal animals, K-NPPase activity was localized to the internodal axolemma and Schmidt-Lanterman incisures. In the Ranvier nodes, enzyme activity was observed along the paranodal and nodal axolemma. In reserpinized nerves, K-NPPase activity was absent along the internodal axolemma and Schmidt-Lanterman incisures. In the Ranvier nodes, however, enzyme activity was detectable only in the nodal axolemma. The reserpinized animals demonstrated no evidence of facial palsy. Because K-NPPase is essential for nerve conduction, these results indicate that the location of enzyme activity in reserpinized animals, namely the nodal axolemma, may be of prime importance in saltatory nerve conduction.