| Every spinal nerve was communicated with spinal cord by ventral root (VR) and dorsal root (DR) of which was motor nerve and sensory nerves respectively. Most nerve root axons were extramedullary with the myelin sheath of Schwann cell, and only a small part of them were embedded centrally in oligodendrocyte and astrocyte. Sensory neurons of the dorsal root ganglia (DRG) was pseudounipolar neuron in which send out not only central processe to constitute the dorsal root and enter spinal cord, but peripheral processe converge toward ventral root to forme spinal nerve and connected with peripheral receptor or effector. Both mechanical and chemical stimulation initiate the electrical activity and transmission of neurotransmitter along afferent fiber from peripheral nerve endings to ganglion, and to spinal cord finally along the dorsal root to produce sensation and modulate muscle's motion.The nerve fibers of ventral and dorsal root were parallel alignment and had poor extensibility for lower contents of collagen fiber. Peripheral nerve fibers were plexi-form arrangement with well extensibility. Furthermore, there were only blood-nerve barrier existed on the capillary wall of endoneurium in spinal nerve root for the lack of epineurium and perineurium. But, the protection provided by blood-nerve barrier and perineurium cells were far from perfect in ganglion neuron with gap junction between capillary endothelial cells. There were material and morphological basis in ganglion for the mutually regulatory of sensory and motor information. DRG were responible for transmitting information about the body's external and internal environments to the spinal cord. Dorsal root injury led to sensory afferent pathway interruption by which were strongly related to sensory loss and motion abnormality for motor reflection had been destroyed.The treatment and recovery of neurological disfunction induced by paraplegia, cauda equina injury, brachial plexus root avulsion, and so on, imposed under high impact energy conditions, had been a huge difficulties faced by our nation with the frequently-occurring traffic and architectural accident. Xiao CG, et al. proposed that anastomosis of rat L4 VR to L6 VR, to set up an artificial somatic-autonomic reflex arc. Hou CL, et al. had re-established a artificial "patellar ligament-spinal cord center-bladder" reflex pathway both in dog by intradural micro-anastomosis of the L6 VR to S2 VR and in a paraplegia patient by autogenous sural nerve bridge grafting anastomosis of the T11 VR to S2 VR. All of their research and clinic outcome had been proved that the artificial reflex arc had been established successfully and effectively after the regeneration of ventral root axon. However, a remarkable difference existed between the abilities of ventral root and peripherally and centrally projecting branches of sensory axons to regenerate, by which neural functional recovery was still a difficult problem.The reason for the lack of functional restitution was that regenerating axons invariably fail to penetrate the dorsal root entry zone (DREZ) in which the environment was so replete with inhibitory cells and extracellular martrix molecules, and to reconnect with their lost central targets in spinal cord after dorsal root was injured in adult mammals. At present, some strategies to promote axon regeneration had involved:(1) boosting the regenerative capacity of the damaged sensory neurones by use of ciliary neurotrophic factor (CNTF), acidic fibroblast growth factor (aFGF), and so on. (2) keeping away from the inhibitory nature of the DREZ with such permissive substrates as peripheral nerve grafts, or replacing them with such regeneration-capable cells as embryonic stem cell or olfactory ensheathing cell transplantation. But most of the measures described above were not suitable for human beings.In our study, we tried to establish a new anastomosis operation for dorsal root regeneration and retain sensory axons intact in DREZ. Our work efficiency and the effects of nerve regeneration were evaluated by Neuro-DiI and horseradish peroxidase (HRP) neural tracing, calcitonin gene-related peptide (CGRP) immunohistochemistry, survival rate of neurons assessed by Nissl staining, regenerative nerve observed by Bielschowsky and myelin staining and transmission electron microscope. Objective:To provide the morphological evidence for axonal regeneration after the dorsal root were transected and anastomosed partially.Method:SD rats were randomly divided into experimental group and sham operation group. L4 and L6 DR in right side were exposed and divided equally into two bunches in which one of them was transected randomly and distal stump were cross reanastomosed, but no anastomosis was performed in sham operation group. L4 and L6 DR on the left side keep intact served as normal control group. Three months postoperation, Neuro-DiI were injected to L4 and L6 DRG for neural tracing. The distribution of CGRP-nerve fibers in DREZ were detected by immunohistochemistry. Nerve fibers were counted by Bielschowsky staining in all groups.Result:At the 3th month after operation, DiI positive marked ganglion neurons and regenerative nerve fibres in stoma were found in experimental group. The distribution density of CGRP-axon in L4 spinal dorsal horn was no significant difference in experimental group (P>0.05), but was decreased significantly in sham operation group than that in normal control group (P<0.05). The quality and quantity of the axonal regeneration in normal control group was no significant difference compared with the experimental group (P>0.05), but showed significant difference with sham operation group (P<0.05) in which decreased significantly.Conclusion:Dorsal root has the capacity of regeneration after partical incision and anastomosis. Morphological evidence for information transmission existed in both ipsilateral DRG.Part Two:Experimental observation of repair after transection of dorsal rootObjective:To explore a effective repairing mode after dorsal transetion for reconstruction of sensory afferent pathway.Method:SD rats were randomly divided into group A, B and C. The right DR of L6 was cut more proximally in all groups. In addition, in group A, L4 DR in right side was cut at a point of pre-ganglia 3-5mm, and its proximal stump was anastomosed to the distal stump of the L6 DR. In group B:The right DR of L4 was cut at a point of post-ganglion 3mm, and its proximal stump was anastomosed to the distal stump of the L6 DR. In group C:under the same operative manipulation in group B, but no anastomosis was performed to serve as the sham operation group. L4 and L6 DR on the left side keep intact served as normal control group. Three months postoperation, Neuro-DiI were injected to L6 DRG for neural tracing. The distribution of CGRP-axon in DREZ were detected by immunohistochemistry. Regeneration nerve fibers were observated by histological stain and electron microscopy in all groups.Result:At the 3th month after operation, DiI marked nerve fibres in stoma were found both in group A and B. The mean number of nerve and the thickness of myelinated axon was no significant difference in group A and B (P>0.05), but was decreased significantly in group C compared with normal control group (P<0.05). CGRP-axon stoped at DREZ in group A, but across the DREZ into the spinal cord, and DiI labeled neuron in L4 DRG was found in group B. The distribution density of CGRP-axon in spinal dorsal horn was no significant difference in group B (P>0.05), but was decreased significantly in group A and C compared with normal control group (P<0.05).Conclusion:Sensory nerve axon were unable to across the DREZ following pre-ganglion incision, but capable of treating axon outgrowth through DREZ when anastomosis was performed post-ganglia. The method of repairing transected DR was achieved by using of post-ganglia anastomosis.Part Three:The neural tracing and morphological study on the change of ventral/dorsal horn and DRG neurons after repairing transected ventral and dorsal rootObjective:To examine whether the signal transduction pathway was smooth or not and the survival of ventral/dorsal horn and DRG neurons after VR and DR axons regeneration, so as to lay histologic foundation for both sensory and motor recovery.Method:SD rats were randomly divided into group A, B and C. In group A:The proximal stump of the L4 VR was anastomosed to the distal stump of the L6 VR in right side. In addition, the right DR of L4 was cut at a point of pre-ganglia 3-5mm as well as ipsilateral L6 DR cut proximal to spianl cord. The proximal stump of the L4 DR was anastomosed to the distal stump of the L6 DR. In group B:The proximal stump of the L4 VR was anastomosed to the distal stump of the L6 VR in right side. In addition, the right DR of L4 was cut at a point of post-ganglion 3mm as well as ipsilateral L6 DR cut proximal to spianl cord. Coaptation between the proximal stump of the L4 DR and the distal stump of the L6 DR was achieved. In group C:under the same operative manipulation on group B, but no VR and DR anastomosis was performed to serve as the sham operation group. L4 and L6 DR on the left side keep intact served as normal control group. Three months postoperation, HRP were injected to sciatic nerve and L6 DRG for neural tracing. The number of ventral/dorsal horn and DRG neurons were counted by Nissl staining for detecting the cell survival in all groups.Result:HRP retrograde tracing demonstrated axonal axoplasmic transport of regenerative nerve recovered well, and HRP positive neurons were identified in the L4 ventral and dorsal horn and L4 DRG in group B, but were noted in the L4 ventral horn only in group A. Survival rate of motor neurons had no significant difference in group A and B (P>0.05), but had decreased significantly in group C compared with normal control group (P<0.05). Survival rate of neurons in the dorsal horn had no significant difference in group B (P>0.05), but had decreased significantly in group A and C compared with normal control group (P<0.05). Survival rate of DRG neurons had no significant difference between all groups(P>0.05).Conclusion:DR anastomosis pre-ganglion has more severe effects on cell survival in dorsal hcrn neurons than post-ganglia, a surgical mode which does not affect the DRG in short-term. Efferent and afferent pathways had been estabilished by spinal nerve anastomosis between L4-L6 VR and DR.
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