c-fos protein like immunoreactivity in non-neuronal cells of rat peripheral nerve after transection.

The induction of c-fos protein (Fos) in non-neuronal cells of rat sciatic nerve was studied immunocytochemically after transection. As soon as 1 h after transection a few Fos-positive Schwann cells and fibroblast-like cells were seen around the wound margins. In the epi-perineurial fibroblast-like cells Fos-like immunoreactivity (Fos-LI) was most intense at 3 h postoperation, but no Fos-LI was seen at 6 days postoperation. In Schwann cells Fos-LI was spread throughout the distal nerve segment at 6 days postoperation, when the staining (in these cells) was most intense. Fos-immunoreactive Schwann cells in the distal nerve segment were still detectable at 14 days postoperation. In the proximal nerve segment positively labelled Schwann cells were observed only 1 and 3 h postoperation and were localized near the site of injury. The results show that the loss of nerve fibers induces a long-lasting expression of Fos or Fos-related antigens in a peripheral nerve.