Role of calpain in spinal cord injury: increased calpain immunoreactivity in rat spinal cord after impact trauma.

Impact spinal cord injury (20 g-cm) was induced in rat by weight drop. The immunoreactivity of mcalpain was examined in the lesion and adjacent areas of the cord following trauma. Increased calpain immunoreactivity was evident in the lesion compared to control and the immunostaining intensity progressively increased after injury. The calpain immunoreactivity was also increased increased in tissue adjacent to the lesion. mCalpain immunoreactivity was significantly stronger in glial and endothelial cells, motor neurons and nerve fibers in the lesion. The calpain immunoreactivity also increased in astrocytes and microglial cells in the adjacent areas. Proliferation of microglia and astrocytes identified by GSA histochemical staining and GFAP immunostaining, respectively, was seen at one and three days after injury. Many motor neurons in the ventral horn showed increased calpain immunoreactivity and were shrunken in the lesion. These studies indicate a pivotal role for calpain and the involvement of glial cells in the tissue destruction in spinal cord injury.