Axonal Transport and Morphological Changes Following Nerve Compression

Abstract

Axonal transport and morphological changes were studied in the rabbit vagus nerve after the nerves had been subjected to compression at either 0, 50 or 200 mmHg for two hours. Slow axonally transported proteins, tubulin and actin, were radiolabelled with ³⁵S-methionine two, seven or 14 days after the injury and the distribution of radiolabelled tubulin and actin within component b of slow transport was measured three days later by densitometric analysis of fluorographs of polyacrylamide gel. No significant differences were found in the distribution of tubulin two (50 and 200 mmHg) or seven (200 mmHg) days after injury, but at 14 days (200 mmHg) there was significantly increased radiolabelling of tubulin relative to actin in the nerve 60 to 70 mm from the nodose ganglion. Morphometric measurements of the nerve cell bodies two days after the compression injury at 200 mmHg revealed no significant changes. Previous work has shown that morphological changes, similar to those found after axotomy, were present in nerve cell bodies seven days after a compression injury. This, taken together with the present results, indicates that compression can induce both morphological and biochemical changes in the neurone. The altered axonal transport of tubulin associated with nerve injury follows a slower time course and does not precede the morphological changes. The findings may be of relevance when discussing the double crush syndrome.