[Effects of physical training on pyramidal tract regeneration in hypertensive rats with focal cerebral infarction]

To explore the effects of exercise training on motor functional recovery and pyramidal tract regeneration in hypertensive rats with focal cerebral infarction.

Middle cerebral artery occlusion (MCAO) model was generated by electric coagulation on stroke-prone renovascular hypertensive Sprague-Dawley rats. The rats were randomly allocated to three groups of sham (n = 15), exercise training (n = 10) and control (n = 12). The exercise training group had running wheel exercise. The neurological function was evaluated with the modified neurological severity scores (mNSS) and forelimb grip strength test at Days 3, 7, 14, 21, 28, 35 and 42 post-ischemia. The pathological changes of neurons around infarct cortex were measured by Nissl staining. At Day 42 post-ischemia, anterograde tract tracers of biotinylated dextran amine (BDA) and cascade blue-labeled dextran amine (CB) were injected into cortex. And axonal extension of ipsi- and contra-lesional pyramidal tract was observed at Day 14 post-injection.

The mNSS score declined in the exercise training group (4.0 ± 1.1, 2.7 ± 0.7, 2.6 ± 0.5) versus those in the control group (6.0 ± 1.3, 5.6 ± 1.0, 5.6 ± 1.1) at Days 28, 21 and 35 post-ischemia (all P < 0.01). The grip strength of paralytic forelimb increased in the exercise training group ((379 ± 41, 344 ± 15, 430 ± 48, 471 ± 47, 454 ± 17)g) versus those in the control group ((276 ± 8, 170 ± 5, 236 ± 12, 283 ± 14, 317 ± 15)g) at Days 14, 21, 28, 35 and 42 post-infarction (all P < 0.05). Compared with the control group (0.571 ± 0.060) , exercise training (0.734 ± 0.035) reduced neuron loss (P < 0.05). Moreover, the percentage of the number of BDA-positive, midline-crossing fibers over the number of labeled fibers in cerebral peduncle ipsilateral to injection site increased in the exercise training group (0.096 8 ± 0.022 6) versus those in the control group (0.014 2 ± 0.003 9) at the level of cervical enlargement (P < 0.016 7). The percentage of CB immunofluorescence in striatum ipsilateral to lesion-sided motor cortex over those in ischemic cortex was lower in the control group (0.521 ± 0.020) and the exercise training group (0.499 ± 0.034) than that in the sham group (0.824 ± 0.017) (all P < 0.01). However, no significant difference existed between control and exercise training groups (P > 0.05).

Exercise training promotes the recovery of motor function and contralesional pyramidal tract regeneration after cerebral infarction.