Changes in nerve conduction in experimental allergic neuritis

Abstract

Alterations in nerve conduction associated with the presence of histological changes were studied in experimentally produced allergic neuritis in guinea pigs. Heterologous peripheral nerve was injected into 59 animals. Electrical recordings were made from sciatic nerves stimulated in vitro and those removed from affected animals. Mildly affected animals with some myelin degeneration often showed no electrical abnormalities. Many severely affected animals died which resulted in recordings being obtained from only 10 animals. These showed conduction block in some fibers and slowing of conduction velocity in other fibers. Repetitive stimulation depressed the action potential. Microscopic examination of the nerve trunks showed foci of cellular infiltration and demyelination. Some single fibers showed widening of the nodal gap. Segmental demyelination over one or more internodes with normally myelinated internodes on either side was also seen. Wallerian degeneration was noted only occasionally. A hypothetical explaination of the slowing of conduction and post-tetanic depression is that the action potential is conducted across some of the demyelinated internodes to excite the myelinated fiber on the other side. Another possibility, however, is that in cases of allergic neuritis the special properties of affected nerves are related to some unknown mechanism.