Abstract: Objective To explore the effects of early exercise on motor function and the mechanism in rats after focal cerebral ischemia. Methods 21 Sprague-Dawley male rats were divided into control group (n=7), natural recovery group (n=7) and exercise training group (n= 7), and the latter 2 groups were modeled with middle cerebral artery occlusion. The exercise training group received wheel running exercise 24 hours after modeling for 14 days. They were assessed with Rogers score and beam balance test 21 days after modeling. 4 rats in each group received routine MRI and diffusion tensor imaging (DTI) scanning. The fractional anisotropy (FA) and apparent diffusion coefficient (ADC) of ischemic (L) and contralateral side (R) were measured, and the rate of them (L/R, r) was calculated. Results There was significant difference in Rogers score among the groups (Z=-0.786, P<0.001), but no significant difference between the natural recovery group and the exercise training group (P>0.05). Beam balance score of the natural recovery group was significantly different from the control group and the exercise training group (F=38.11, P<0.001), but there was no significant difference between the latters (P>0.05). The LFA of the natural recovery group was significantly different from the control group (P<0.05), but not significantly different from the exercise training group (P>0.05); while the rFA of the natural recovery group was significantly different from the control group and the exercise training group (F= 19.30, P<0.05). LADC and rADC might be different between the control group and the natural recovery group (P=0.056, P=0.057), but not significantly different between the natural recovery group and the exercise training group (P>0.05). LFA and rFA strongly correlated with all the behavior scores (r=-0.90--0.70, P<0.01); while LADC and rADC moderately correlated with the behavior scores (r=0.50-0.75, P<0.05), except balance (P>0.05). DTT showed that the direction and density of neural fibers were significantly asymmetrical in the natural recoverygroup and the exercise training group, and more symmetrical in the exercise training group. Conclusion Early exercise can promotethe neural functional recovery in rats after focal cerebral ischemia, which may associate with the improve of conduction of fibers.

Key words: stroke, cerebral ischemia, exercise, diffusion tensor imaging, neural fibers, rats