Effects of repetitive transcranial magnetic stimulation at different intervention time on motor function recovery after spinal cord hemisection in rats

English Keywords:Spinal cord injury  Repetitive transcranial magnetic stimulation  Spinal cord hemisection  Functional recovery  Rat

English Abstract:

  【Abstract】 Objectives: To observe the effect of repetitive transcranial magnetic stimulation(rTMS) on motor function recovery at different intervention time after spinal cord hemisection in rats. Methods: 42 SD rats were separated into five groups randomly, including normal control group(n=6),　sham group(n=6), SCI group(n=10), ArTMS group(n=10) and SrTMS group(n=10). T10 spinal cord hemisection model was made in SCI group, ArTMS group and SrTMS group. In sham group, the vertebral laminae of rats were removed while keeping spinal cord intact. The rats in normal control group did not receive any surgery.　RTMS(10×5sec bursts of 10Hz at 35% maximal stimulator output,　each burst separated by a 2min interval) was delivered daily 5 days per week for 2 weeks.　The treatment began at 4 days after surgery for acute group(ArTMS group) and 18 days after surgery for subacute group(SrTMS group). The rats in normal control group, sham group and SCI group did not receive any intervention. Motor functional recovery was assessed by using BBB locomotor rating scale and the Horizontal Ladder Scale before surgery and at 3 days, 10 days, 17 days, 24 days,　31 days,　38 days after surgery. The tibialis anterior was surgically removed for observing muscle shape, and diameters of different muscle types were merssured by ATPase staining(pH 4.6) at 38 days after surgery. Results: The BBB score(21) and the percentage of correct steps of Horizontal Ladder Scale(100%) were normal in normal control group, sham gourp and SCI group, ArTMS group, SrTMS group before surgery, which remianed unchangeed in sham group after surgery compared with those before surgery. The BBB score and the percentage of correct steps in SCI group, ArTMS group and SrTMS group at 3 days after surgery decreased significantly compared with those before surgery. The BBB score of SCI group and SrTMS group at 31 days and 38 days after surgery and the percentage of correct steps at 24 days, 31 day, 38 days after surgery improved significantly compared with those at 3 days and 10 days after surgery(P<0.05). In ArTMS group, the BBB score increased significantly at 17 days, 24 days, 31 days, 38 days after surgery compared with those at 3 days and 10 days（P<0.05）. The BBB score and the percentage of correct steps between SCI group and SrTMS group showed no difference from 3 days to 38 days after surgery. The BBB score and the percentage of correct steps in ArTMS group at 3 days and 10 days after surgery showed no significant difference compared with those in SCI group and SrTMS group. The BBB score of ArTMS group at 17 days, 24 days, 31 days and 38 days after surgery improved significantly compared with those in SCI group and SrTMS. The Horizontal Ladder Scale of ArTMS group was significantly higher at 17 days, 24 days, 31 days, 38 days after surgery than SCI group and was higher at 24 days, 31 days, 38 days after surgery than SrTMS group（P<0.05）. ATPase staining of paralysis tibialis anterior of right low limb showed the diameters of Ⅰ, 2A, 2B type muscle fibers in SCI group decreased compared with normal control group and sham group（P<0.05）. The diameters of type 2A muscle fibers decreased in ArTMS group than in normal control group and sham group（P<0.05）. The diameters of type 2A and 2B muscle fibers were significantly greater in ArTMS group than those in SCI group（P<0.05）, but for 1 type muscle fibers there was no significant difference between ArTMS group and SCI group. In SrTMS group, the diameters of 2A and 2B muscle fibers significantly decreased compared with normal control group and sham group（P<0.05）, and 2B muscle fibers decreased significantly than those of ArTMS group（P<0.05）. Conclusions:　rTMS in acute stage of SCI improves the functional recovery and alleviate muscle atrophy partially after spinal cord hemisection in rats, which shows better effect than subacute stage.