INVASION OF THE RAT VENTRAL ROOT L5 BY PUTATIVE SYMPATHETIC C-FIBERS AFTER NEONATAL SCIATIC-NERVE

The present study examines the occurrence of C-fibers in lumbar ventra l roots after sciatic nerve crush in neonatal and adult rats. Electron microscopic analysis showed that the number of C-fibers in the ventra l root L5 increased significantly on the lesion side after neonatal bu t not adult sciatic nerve crush and that the number of C-fibers was hi gher in the ventral root L5 on the unoperated side compared to this ro ot in normal control rats. In order to determine whether the new C-fib ers in the L5 root on the lesion side are sensory or sympathetic we ma de immunohistochemical studies on roots from neonatally crushed rats. We found that there was no obvious lesion side/contralateral side or o perated rat/control rat difference with respect to the occurrence and general configuration of axons with substance P-, calcitonin gene-rela ted peptide- or vasoactive intestinal polypeptide-like immunoreactivit y. However, the occurrence of axons with tyrosine hydroxylase-like imm unoreactivity appeared clearly higher in the ventral root L5 on the le sion side compared to the unoperated side in neonatally crushed rats. Moreover, these axons seemed to be more numerous also in the Ventral r oot L5 on the unoperated side compared to normal control rats. No lesi on side/contralateral side or operated rat/control rat differences wer e seen in the ventral root LA. We propose that the ventral root L5 is invaded by putative sympathetic C-fibers after sciatic nerve crush les ions in newborn rats.