Disruption of the perineurium in amphibian peripheral nerve: morphology and physiology.

Removal of a small piece of perineurium in amphibian nerve causes a lesion consistent with the presence of extensive demyelination. Conduction velocity is reduced by 30 to 40%, and most of the fibers that still conduct are labile, with abnormally low blocking temperatures and unusual susceptibility to conduction block induced by changes in extracellular electrolytes. Application of drugs that inhibit the delayed K+ conductance restores conduction to fibers blocked by temperature elevation and ionic changes. This preparation may prove useful in studies of the pathophysiology of demyelinating diseases.