Regenerating dorsal roots and the nerve entry zone: an immunofluorescence study with neurofilament and laminin antisera.

Dorsal spinal roots were crushed in 30 rats at the lumbar or thoracic level. Peripheral roots, nerve entry zone, and spinal cord were studied 3 to 5 weeks after operation by immunofluorescence with neurofilament, glial fibrillary acidic (GFA), and laminin antisera. As previously shown in sciatic nerve undergoing Wallerian degeneration, reactive Schwann cells forming the bands of Büngner stained intensely with laminin antisera. Within these bands bundles of regenerating axons were present as indicated by double staining with laminin and neurofilament antisera. With very few exceptions, regenerating axons were not observed in the laminin-negative intramedullary division of the root. This also appeared to be the case when the dome-shape protrusion of central nervous system tissue forming the intramedullary division was surrounded by regenerating fibers. Compared with GFA antisera, laminin antisera allowed a better identification of the boundary between the central and peripheral nervous systems. In the central nervous system only blood vessels were laminin-positive, whereas Schwann cells' processes were decorated by GFA antisera in peripheral roots, the staining being stronger in reactive Schwann cells.