Nerve growth factor in glia and inflammatory cells of the injured rat spinal cord

Nerve growth factor (NGF) is crucial for the development of sympathetic and small-diameter sensory neurons and for maintenance of their mature phenoty pe, Its role in generating neuronal pathophysiology is less well understood . After spinal cord injury, central processes of primary afferent fibers sp rout into the dorsal horn, contributing to the development of autonomic dys functions and pain. NGF may promote these states as it stimulates sprouting of small-diameter afferent fibers and its concentration in the spinal cord increases after cord injury. The cells responsible for this increase must be identified to develop a strategy to prevent the afferent sprouting. Usin g immunocytochemistry, we identified cells containing NGF in spinal cord se ctions from intact rats and from rats 1 and 2 weeks after high thoracic cor d transection. In intact rats, this neurotrophin was present in a few ramif ied microglia and in putative Schwann cells in the dorsal root. Within and close to the lesion of cord-injured rats, NGF was in many activated, ramifi ed microglia, in a subset of astrocytes, and in small, round cells that wer e neither glia nor macrophages, NGF-immunoreactive putative Schwann cells w ere prevalent throughout the thoracolumbar cord in the dorsal roots and the dorsal root entry zones. Oligodendrocytes were never immunoreactive for th is protein. Therapeutic strategies targeting spinal cord cells that produce NGF may prevent primary afferent sprouting and resulting clinical disorder s after cord injury.