Regeneration of dorsal root fibers into the adult rat spinal cord

Regeneration of dorsal root nerve fibers into the spinal cord of adult rat was studied with the electron microscope after crushing the roots. Regenerated dorsal root myelinated fibers were observed in the substantia gelatinosa and posterior funiculi around the tenth week after lesion. Cytoplasmic processes of oligodendrocytes were often found close to the young myelinated nerve fibers. The astrocytic response subsided as regeneration progressed. Clusters of small, circular profile of cellular processess were found in the neuropil about the sixth week and are considered to be regenerated unmyelinated axons. At this period, groups of segments of cellular processes containing clear vesicles were also encountered in the substantia gelatinosa and resembled growth cones described in peripheral regenerating nerves.