Ultrastructural changes in the rat spinal cord after temporary occlusion of the thoracic aorta

Summary Occlusion of the aorta of the rat between the fourth and fifth thoracic vertebrae produces focal ischemic lesions of the gray matter of the lumbar spinal cord. Two types of lesions can be distinguished.Type A shows transient parapareses of the hind limbs due to diffuse injury of the lumbar gray matter, consisting of disseminated necrosis of small and middle sized neurons and reactive gliosis.Type B is characterized by irreversible spastic paraparesis due to necrosis of the center of the anterior horn, the zona intermedia and the posterior horn. The astroglia demonstrates characteristic reactions in the developing necrosis of the gray matter: retraction of processes with condensation of the perikaryon and segmentation or rupture of swollen processes leading to disintegration of the neuropil. Microcirculatory disturbances may intensify the tissue reactions in the postischemic period, initiating the focal necrosis of the central gray matter.