The Effect Of Exercise Training On The Functional Recovery Of Rats With Spinal Cord Injury After Blocking The BDNF-TrkB Pathway

Background:Intrathecal catheterization(subarachnoid space catheterization)is a common mode of subarachnoid space administration in practice.However,in the rat model of spinal cord injury(SCI)in T10,there is no uniform method of intrathecal administration to subarachnoid space of spinal cord.Objective:To explore an intrathecal catheterization method that suitable for T10 SCI rats model,which can be better used for dosing subarachnoid space in SCI model.Methods:60 female SD rats were randomly divided into L3-4 catheterization group(T group)and L6-S1 catheterization group(group C).After 7 days of intrathecal catheterization and SCI,the differences between two types of intrathecal catheterization in disability rate,mortality,biting catheter rate,lidocaine test,weight changes and blue ink location test were compared.After 7 days of SCI,Alzet osmotic pumps were implanted into two groups respectively,then observing the mortality,weight and the morphology of the spinal cord after long-term catheter and osmotic pumps implanted in SCI rats.Results:After 7 days of intrathecal catheterization and SCI,two groups of biting catheter rate had significant difference(P<0.05),total elimination rate had significant difference(P<0.01).After intrathecal catheterization and SCI,two groups were weight lose,and after 35 days of intrathecal catheterization,T group rats’ weight higher than C group(P<0.05),Blue ink location test showed there was no appearance of catheter obstruction and position migration in two groups.After 4 weeks of Alzet osmotic pumps implanted,the histocompatibility of Alzet osmotic pumps were well.HE staining showed that the lumbar spinal cord in two groups all been compressed mildly.Conclusion:The L3-4 intrathecal catheterization is ideal for SCI model in rats,because the biting catheter rate and mortality is lower,and the operation is easier.Background:Exercise training can promote the expression of Brain-Derived Neurotrophic Factor(BDNF)and Tropomyosin-related kinase B(TrkB)in spinal cord after SCI,and promote the recovery of motor function of spinal cord injury(SCI)rats through various mechanisms.However,after exercise training,whether BDNF plays a key role in the repair of nerve after SCI is still unclear.Objective:In this study,we used TrkB blocker to blocking the BDNF-TrkB signaling pathway,and investigated the effects of BDNF that induced by Body-weight support treadmill training(BWSTT)on motor function,secondary injury of lumbar spinal cord,neuronal activity and synaptic plasticity,and further discussed the mechanism of BWSTT on locomotor function recovery after SCI.Methods:This study was divided into two parts,and a total of 56 SD rats were needed:Part 1:In order to investigated the effect of BWSTT on BDNF and TrkB expression,24 rats were randomly divided into:sham operated group(Sham group),SCI control group(SCI-Sed group)and SCI treadmill training group(SCI-TT group).Part 2:In order to investigated the effect BDNF-TrkB signaling pathway in recovery of locomotor function in SCI rats after BWSTT,32 rats were randomly divided into:SCI+PBS control group(SCI-Sed-PBS group),SCI exercise+PBS group(SCI-TT-PBS group),SCI+TrkB/Fc control group(SCI-Sed-TrkB/Fc group)and SCI exercise+TrkB/Fc group(SCI-TT-TrkB/Fc group).All rats in two part of this study were underwented SCI operation.In part 2 of this study,intrathecal catheterization was operated 1 week before SCI operation,and 7 days after SCI,TrkB blocker was used to blocking BDNF-TrkB signaling pathway.All the exercise group rats were trained for 4 weeks by BWSTT 1 week after SCI.The locomotor function were assessment evaluated with BBB at 1 day,3 day 3,1 week,2week,3 week and 4week after SCI.At the end of this study,the L2-5 spinal segments of all rats were taken after sacrificed.In part 1 of this study,immunohistochemistry and western blot were used to detect the BDNF and TrkB expression in distal spinal segments.In Part 2 of this study,nissl staining was used to investigated the morphology and quantity of motor neurons,and immunohistochemistry technology was used to detect the NeuN,GFAP,PSD-95,and SYP expression in distal spinal segments,and western blot was used to detect the PSD-95 and SYP expression in distal spinal segments.Results:1)BWSTT can promote the recovery of motor function of SCI rats,and increase the expression of BDNF and TrkB in injured spinal cord.2)After blocking the BDNF-TrkB pathway,the effect of BWSTT on the motor function recovery of SCI rats was inhibited.3)Immunohistochemistry of the distal spinal segments showed that,after BDNF-TrkB pathway blocked,the NeuN,GFAP,PSD-95,and SYP expression in spinal cord were reduced compared with un-blocked rats underwent BWSTT.4)Western blot of the distal spinal segments showed that,after BDNF-TrkB pathway blocked,the PSD-95 and SYP expression in spinal cord were reduced compared with un-blocked rats underwent BWSTT.Conclusion:BWSTT can promote the recovery of motor function in SCI rats,and enhance the expression of BDNF and TrkB in distal spinal segments of the SCI rats.Blocking the BDNF-TrkB signaling pathway inhibits the effect of BWSTT on the locomotor function recovery,neuronal activity and neuronal plasticity in SCI rats.Thus,the BDNF-TrkB signaling pathway is the key way to improve the function recovery by exercise training in SCI rats.