Deteriorating stroke model: histopathology, edema, and eicosanoid changes following spinal cord ischemia in rabbits.

Secondary motor dysfunction is often observed following ischemic episodes in the central nervous system. To study potential mechanisms of postischemic motor deterioration, we developed a rabbit spinal cord ischemia model that has characteristics similar to the clinical condition termed deteriorating stroke. In this model, 70% of the rabbits regained substantial motor function by 4 hours after complete hindlimb paralysis during lumbar spinal cord ischemia; however, over the next 20 hours motor function steadily declined to the point where only 30% of the rabbits had minimal hopping function. The role of eicosanoids in spinal cord ischemia was studied by radioimmunoassay of several prostaglandins (6-keto-PGF1 alpha, PGE2, and TxB2) in the spinal cord. After 5 minutes of reperfusion, TxB2 levels were markedly elevated (p less than 0.05) while 6-keto-PGF1 alpha levels did not change. The TxB2:6-keto-PGF1 alpha ratio was also significantly increased. After 30 minutes of reperfusion, PGE2 levels were also elevated (p less than 0.05). Tissue edema measured by microgravimetry was also increased after 30 minutes of reperfusion in both gray and white matter. By 4 hours of reperfusion, rabbits regained near-normal hindlimb motor function while PGE2, 6-keto-PGF1 alpha, TxB2, and tissue water content were back to normal. However, by 18 hours of reperfusion, when hindlimb function was deteriorating, TxB2 levels were elevated again, and edema in gray and white matter was increased as was the number of necrotic neurons observed by light microscopy. These results suggest that the secondary deterioration of motor neurologic function was due to the excess formation of TxA2 primarily in the late reperfusion phase. However, further studies are necessary to elucidate the relation of TxA2 with ischemic neural injury.