Morphological characterization of the evolving rat spinal cord injury after photochemically induced ischemia.

We have characterized the evolving morphological changes in the adult rat spinal cord following photochemically induced spinal cord ischemia. In cresyl violet-stained sections, disintegration of the tissue at the epicenter was evident at 6 h. This was preceded at 1 h post ischemia by an albumin immunoreactivity. The albumin immunoreactivity was increased at 6 and even more so at 24 h post ischemia. At 72 h post ischemia the albumin immunoreactivity was decreased. The size of the lesion was established by 3 days after the onset of ischemia. During the 1st week post ischemia, neurofilament (NF) immunohistochemistry showed swollen axons adjacent to the injured tissue. From 2 weeks post ischemia an increasing number of regrowing NF-immunoreactive axons could be seen in the center of the necrotic cavity. At 3 weeks after ischemia, a developing gliosis was observed around and rostral to the lesion cavity, as evidenced by increased glial fibrillary acidic protein (GFAP) immunoreactivity. The gliosis became more pronounced until 6 weeks post ischemia, at which time enlarged GFAP-immunoreactive cells could be seen in the remaining viable tissue bordering the necrotic areas. In this study we show that several traits in the development of a spinal cord lesion after photochemically induced ischemia are similar to those described previously after traumatic spinal cord lesions.