The Study Of Synaptic Plasticity In The Rat Lumbar Ventral Horn After Spinal Cord Hemisection

PartⅠSpontaneous functional recovery of the rat hindlimb after thoracic spinal cord hemisectionPurpose:To investigate the functional locomotor recovery of the rat hindlimb by inclined plane method,Tarlov grading and BBB scale after spinal cord hemisection in T10.Methods:Sixty six adult Sprague-Dawley rats(200-250g) were randomly divided into experimental,sham operation and normal control group.The rats in experimental groups and sham operation group were subdivided into 12h,3d,7d,14d and 21d subgroups,based on the survival time alter operation.The rats in the experimental groups were hemisected the right half of spinal cord at T10.The vertebral lamina were removed at the same site in the sham operation rats.And the normal rats served as controls without any treatment.Motor function of hindlimb of all rats were detected by inclined plane method,Tarlov grading and BBB scale at the point of survival time.Results:The experimental group rats lost almost locomotor function in the hindlimb and the scores of inclined plane method,Tarlov grading and BBB scale all decreased at 12h(p＜0.05) after T10 hemisection,the function and scores began to recover on 3d,and arrived to the normal level on 21d.Conclusion:A wide range of spontaneous hindlimb locomotor recovery could occur in the rat after spinal cord hemiscetion. PartⅡThe study of synaptic plasticity in the rat lumbar ventral horn after spinal cord hemisectionPurpose:Based on the functional recovery of the hindlimb,the expression of synaptophysin(SYN) in the rat lumbar cord was detected to elucidate the synaptic plasticity in the motoneurons and interneurons after spinal cord hemisection in T10.Methods:The experiment animal model and the group division were same as the first part.Sixty six rats were randomly selected to inject fluorogold into the sciatic nerve 5 days before sacrifice,and then SYN double immunofluorescence with fluorogold retrograde labeling in the motoneurons and with calbindin D28k(CB) and calretinin(CR) in the interneurons were observed at the 5th lumbar spinal cord.Then another series rats(n=66) were used to detect the expression of SYN protein in the lumbar cord by Western blot.Then linear correlation and linear regression were tested between BBB scale of the hindlimb and expression of SYN around motoneurons and interneurons.Results:SYN expression around motoneurons and CB/CR-ir interneurons down-regulated in the injured early stage and up-regulated in later stage in lumbar spinal cord.SYN expression around CR-ir interneurons decreased at 12h after injury and recovered to the normal level on 3d.SYN expression around CB-ir interneurons began to decrease on 3d after injury.While SYN expression around motoneurons decreased at 12h after injury,recovered lightly on 3d,then maintained this level, and arrived to the normal level on 21d,suggesting that the recovery was later than that of SYN-ir around CR-ir neuron.Western blot showed that there were no obvious changes in SYN protein ipisilateral to lumbar spinal cord in the injured early stage,while the expression of SYN protein was increased on 21d after spinal cord hemisection.The linear correlation and regression analysis showed there was positive correlation between the BBB scores of hindlimb and SYN protein or the SYN expression surrounding the motoneurons or CR-ir neurons in the lumbar cord after T10 hemisection(r=0.42,p=0.003;r=0.33,p=0.02; r=0.45,p=0.001,respectively).Conclusion:There were the temporal changes of synaptic plasticity in the motoneurons and CB/CR-ir interneurons of lumbar spinal cord following spinal cord hemisection.The linear correlation and regression analysis showed that SYN protein or expression of SYN around motoneurons or CR-ir interneuron was positive correlation with the spontaneous recovery of hindlimb locomotion. PartⅢThe mechanism of synaptic plasticity in the rat lumbar cord after spinal cord hemisectionPurpose:To clarify the underlying mechanism of synaptic plasticity in the motoneurons and interneurons of rat lumbar cord after spinal cord hemisection in T10.Methods:Fifty four adult Sprague-Dawley rats(200-250g) were randomly divided into experimental,sham operation and normal control group.The rats in the experimental groups were hemisected the right half of spinal cord at T10.7th day after the operation,BDA was injected into the left or right hindlimb motor cortex or bilateral gray matter in the fourth cervical cord.All rats were allowed to survival for 21 days.Then the parvalbumin(PV) or CR and BDA immunofluorescence staining were made in C5 spinal cord.And the SYN,PV or CR and BDA immunofluorescence staining were made in L5 spinal cord.Results:There were contacts located between BDA positive CST collaterals and CR/PV-ir interneurons in the both sides of cervical spinal cord.The double staining of BDA positive LPN axons and SYN-ir were seen in the ipisilateral to the injured spinal cord,and contacts between BDA positive LPN axons and CR/PV-ir interneurons were also viewed in the lumbar spinal cord on the 21th day after hemisection.Conclusion:Interneurons and motoneuorns in the lumbar cord contacts with CST collateral sprouting of the injured and uninjured CST by the relay of cervical interneuron or LPN axons on 21d after T10 hemisection,which may be morphological evidence of locomotor recovery following spinal cord hemisection.