ROLE OF CALPAIN IN SPINAL-CORD INJURY - INCREASED CALPAIN IMMUNOREACTIVITY IN SPINAL-CORD AFTER COMPRESSION INJURY IN THE RAT

Spinal cord injury was induced in rats by compression technique using 10 or 20 g compression for 5-10 min. Calpain immunoreactivity was exam ined in the lesion as well as in the adjacent areas of the cord at dif ferent times following injury. Elevated calpain immunoreactivity was f ound in the lesion compared to sham control. The increase in calpain i mmunoreactivity was dependent on the time and the degree of trauma. Ar eas adjacent posterior or caudal to the lesion also showed increased c alpain immunoreactivity. Most of the cells in the dorsal and ventral f uniculi with increased calpain staining were astrocytes and microglia. Proliferation of microglia and/or activation of astrocytes in the les ion, identified with lectin binding GSA and glial fibrillary acidic pr otein staining, was seen at 1 and 3 days after trauma, respectively. E ccentric nuclei and shrunken neurons with increased calpain staining w ere seen in the ventral horn. The extent of increase in calpain immuno reactivity in the lesion was also proportional to the degree of trauma . The elevated calpain immunoreactivity suggests increased calpain exp ression (mRNA), synthesis (protein level), and activity in the lesion of cord following injury as compared to sham control. This finding sup ports a pivotal role for calpain in tissue degeneration in spinal cord trauma.