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We studied the role of antiganglioside antibodies in the pathogenesis of autoimmune neuropathies using an in vitro preparation of a rat sciatic nerve. Human and rabbit sera with high titers of the antibodies were applied to a restricted segment of the sciatic nerve mounted in a recording chamber, and the compound nerve action potentials of the myelinated and unmyelinated fibers were observed. Myelinated fiber conduction became blocked at the segment within a few hours, whereas the unmyelinated fiber conduction remained unchanged. These results suggest that antiganglioside sera directly produce an acute conduction block only in myelinated nerve fibers and that this in vitro model is useful for studying the ionic mechanism by which the acute conduction block occurs.

Using a new collision method, we measured motor nerve conduction velocities of the ulnar nerve in the forearm and the action potential amplitude of the abductor digiti minimi muscle on 60 adults, ages 20 to 82 years and apparently free from diseases of the peripheral nervous system. Both maximal and minimal motor nerve conduction velocities were linear functions of age; 64.42-0.05 age and 60.45-0.12 age, respectively. The percentage of the minimal to the maximal motor nerve conduction velocities was expressed as 94.45-0.13 age. The maximum amplitude of evoked muscle action potentials was also correlated with age. This novel method may be useful in detecting pathology of motor nerve fibers which results in a decrease in submaximal conduction velocities.