AXONAL REGENERATION IN AN ARTICULAR BRANCH FOLLOWING RAT SCIATIC-NERVE LESIONS

This study examines the outcome of axonal regeneration in the posterio r articular nerve of the adult rat knee joint (PAN), after sciatic ner ve lesions. Some animals had previously been subjected to chemical sym pathectomy with guanethidine. In crushed cases the number of myelinate d PAN axons was 50% above control level. The occurrence of C-fibers wa s doubled, mainly due to an increased number of sympathetic efferents. In neurotomy/suture cases the number of myelinated fibers was clearly elevated, but the number of C-fibers was close to normal. Most C-fibe rs were sensory. Similar, but less marked, post-regeneration abnormali ties were seen in the nerve to the lateral gastrocnemius muscle. The s ural nerve exhibited moderately increased numbers of myelinated and un myelinated fibers in crushed cases. In neurotomy cases, the myelinated axons had increased and the C-fibers had decreased in number. The siz e distribution of myelinated PAN axons was less abnormal in crushed ca ses than after neurotomy, like in the other nerves. These results show that the outcome of axon regeneration in an articular branch of the l esioned rat sciatic nerve differs from that in non-articular branches, and suggest that joints may become hyperinnervated by C-fibers after nerve crush lesions.