Effects Of RTMS Combined Exercise Training On Locomotor Function And Neuronal Plasticity In Rats With Incomplete Spinal Cord Injury

Background:After spinal cord injury(SCI),the conduction of ascending and descending fibers is disrupted,and the dynamic interactions among the spinal neuronal network,supraspinal pathways and peripheral sensory inputs are disruptive,resulting in an impairment of locomotor function.Previous studies have suggested that both exercise training and repetitive transcranial magnetic stimulation(rTMS)can promote the recovery of SCI motor function to some extent.Recently,the combination of non-invasive stimulation and exercise training as a rehabilitation strategy has been gradually applied in the clinical rehabilitation of SCI.Objective:To investigate the effect of repetitive transcranial magnetic stimulation(rTMS)combined with exercise training and the sequence of combination on locomotion recovery and neuronal plasticity in rats with incomplete spinal cord injury(SCI).Methods:Sixty Sprague-Dawley rats were randomly divided into Sham operation group(Sham),spinal cord injury control group(Con group),individual exercise training group(ET group),rTMS after exercise training group(ET+rTMS group),and rTMS before exercise training group(rTMS+ET group),12 in each group.In the Sham group,only T9 level laminectomy was performed without SCI.In the Con group,spinal cord contusion model was established without any training.After SCI,only treadmill training was performed in the ET group without rTMS intervention.rTMS was conducted immediately after treadmill training in the ET+rTMS group,while rTMS was conducted before treadmill training in the rTMS+ET group.BBB and neuroelectrophysiology test were performed to evaluate locomotor and distal neuron function before and after operation.After our intervention,magnetic resonance imaging(MRI)was used to detect the injured segment of the rats.The expression of brain-derived neurotrophic factor(BDNF),synapsin I and neurofilament heavy polypeptide(NF200)were measured by immunofluorescence,and Western Blot was used to detected BDNF and synapsin I protein level.Results:(1)After 8-week-treatment,compared with the Con group,BBB scores significantly enhanced in the ET+rTMS group(P<0.05)and rTMS+ET group(P<0.01),and the difference showed statistically significant.Compared with the ET group,the scores in rTMS+ET group were significantly higher(P<0.05).(2)The mean amplitude and chronodispersion(F-CD)of F wave in Sham group remained stable before and after surgery.At the ninth week after surgery,the mean amplitude of Con group was still markedly higher than that of Sham group(P<0.01)and was also significantly higher than that of ET+rTMS group(P<0.01)and rTMS+ET group(P<0.01).The change of F-CD showed that after all the intervention,F-CD decreased to different degrees in the ET+rTMS group and the rTMS+ET group,which were lower than the Con group,and the differences were statistically significant(P<0.05).(3)MRI results showed that the lesion volume in the ET+rTMS group and the rTMS+ET group was significantly smaller than that in the CON group(P<0.01).Compared with the ET group,the lesion volume was also markedly reduced in the ET+rTMS group(P<0.01)and the rTMS+ET group(P<0.001).(4)Immunofluorescence results showed that compared with Con group,the expression of BDNF in ET+rTMS group was significantly increased(P<0.05),and the expression of BDNF(P<0.01),synapsin I(P<0.05)and NF200(P<0.05)in rTMS+ET group were significantly enhanced.Compared with ET group,BDNF expression was gained in rTMS+ET group,and the difference was statistically significant(P<0.05).(5)Western blot results showed that compared with Con group,the protein expression of BDNF in ET group(P<0.05),ET+rTMS group(P<0.001)and rTMS+ET group(P<0.001)was significantly increased,and the protein expression of synapsin I in rTMS+ET group was notably higher(P<0.01).Compared with ET group,BDNF expression in rTMS+ET group was significantly enhanced(P<0.05).Conclusions:rTMS combined with exercise training can enhance the hind limb locomotion of incomplete SCI rats,improving motor control of central nerve and motor neuron plasticity by promoting expression of BDNF,synapsin I and NF200.