Abstract: Objective To explore the effetc of different intensity of exercise on learning ablility and oxygen free radical metabolism in rats after cerebral ischemia-reperfusion (I/R). Methods 60 male Sprague-Dawley rats were randomly divided into sham group, I/R group, aerobic exercise preconditioning group and exhaustive exercise preconditioning group. The morphological changes of neural cells in hippocampus were observed with HE staining, the learning ablility was assessed with shuttle box, the activity of superoxide dismutase and malondialdehyde level in hippocampus were measured with hydroxylamine method and TBA method respectively 1, 3, 7 days after injury. Results The number of survival neurons, active avoidance reaction and activity of superoxide dismutase decreased, and the latency of passive avoidance and malondialdehyde levels increased in all the other groups compare with the sham group (P<0.001). Further more, the number of surviving neurons, active avoidance reaction rate and the activity of superoxide dismutase were less in the I/R group than in the aerobic exercise preconditioning group (P<0.001), and more than in the exhaustive exercise preconditioning group (P<0.001), while the latency of passive avoidance and the level of malondialdehyde was more than in the aerobic exercise preconditioning group (P<0.001), and less than in the exhaustive exercise preconditioning group (P<0.001). Conclusion Regular aerobic exercise is beneficial to protect the learning ability from cerebral I/R in rats, but exhaustive exercise may be negative, which may associated with the metabolism of oxygen free radical in hippocampus impacted by exercise.

Key words: cerebral ischemia-reperfusion, learning, aerobic exercise, exhaustive exercise, oxygen free radical, rats