Changes Of Electrophysiology In Sciatic Nerve And GAP-43 And VEGF Protein Expression In The Injury Spinal Cord Tissue Of Rats

Spinal cord injury (SCI) is an accident for someone, and not only leads to the ability of aesthema and locomotion destroy, but also bring a heavy burden to the relatives of the patiens and the society. Recently there is an ascedning trend in the incidence rate in many countries, due to traffic accidents, falling, violence, physical exersise and so on. As evidenced by the poor neurologic recovery after most spinal cord injuries and the paucity of pharmacologic treatments currently available, it should be obvious to even the most casual observer that our present understanding of these pathophysiologic processes and mechanism is fairly rudimentary.The final consequence of spinal cord injury was determined by primary injury , secondary injury and the repair and anagenesis of injury tissue. Primary injury to the spinal cord immediately disrupts cell membranes, destroys myelin and axons in the longitudinal tracts, and damages microvessels, triggering devastating secondary injury process with the release of various deleterious factors. Multiple cellular and molecular mechanisms of the secondary injury process cause neurodegeneration, working through complex cascades to spread neurodegeneration beyond the site of primary injury. Because of primary injury is inconvertible, the clinical treatment strategies mainly focused on to control secondary injury mediators of SCI. These mediators including two ascepts:(1) free radical, nitrogen monoxidum (NO), platelet activating factor (PAF), excitatory aminacids (EAA), dielectric changes, energy metabolism disorder, lipid peroxidize and apoptosis etc.(2)promoting the repair and anagenesis of injury tissue, for example the secretion of nerve growth factor, GAP-43 and VEGF etc.In 1944, Berry used electrophysiological technique to study and research the anagenesis of peripheral nerve. In 1948, electrophysiological technique was used in clinic by Hodes. And he found the the relation between stimulus intensity and time, and also found that nerve conduction velocity is relative to the injure and anagenesis of nerve. Now electrophysiological technique is an effect method of estimating the ability of nerve.GAP-43, found in 1980s, is a cell membrane phosphoprotein related to neural development, axon anagenesis and synapse rebuinding, so it is an important and decisive factor of repair and anagenesis.There are many GAP-43 proteins and their DNA in cerebellum, cerebrum, spinal cord, posterior root ganglion, autonomic nerve, axon of developing nerve neurons, especially increment borer, and gliocyte. In molecular level, growth of axon when developing and repairing, is related to expressions of growth associated proteins, which have special effect on growth of nerve. GAP-43, a cell membrane phosphoprotein, is full of increment borer, irritates growth of axon through promoting actins aggregation, increasing the ability of increment borer and promoting neurons grow, differentiate and regenerate. There is also reported GAP-43 can make neuron grow without other growth factors, increase neuronal plasticity, and promote transmitter realeasing. Moretto found that there is GAP-43 in glial cells, and GAP-43 is related to skeleton protein.VEGF was found in nutrient medium of follicle cells of cow in 1989. VEGF is special mitogen in vascular endothelial cell. It can not only promote vascular endothelial cell growing, but also induce blood vessel developing through increasing mRNA of PA and PAI, accommodating ability of PA and PAI, and promoting protein out of cell hydrolyzing. Except for these, VEGF also can increase permeability of blood vessel, so it is called ascular permeability factor. In vivo, Lin found there are more neurons of cerebrum, more axons and longer axon with VEGF. Jin reported VEGF can decrease apoptosis of neurons in hippocampus because of hypoxia and alimentary deficiency. In all, VEGF can not only make blood vessel grow, but also provide nourishment for neurons and protect neurons. Vaquero reported VEGFR is found in glial cell in spinal cord, illustrating VEGF can promote glial cell growing, especially astrocyte, then secrete glial cell-line derived neurotrophic factor to support neurons, nourish neurons and protect neurons indirectly. In a word, VEGF is important of repair and anagenesis of spinal cord injury.Now, repair and functional recovery of SCI is hot and difficult. Our laboratory has studied pathematology changes and neuron apoptosis of SCI before. But repair and anagenesis of SCI is still in the air. So we used acute spinal cord injury model, and studied changes of electrophysiology in sciatic nerve and GAP-43 and VEGF protein expression in the injury spinal cord tissue of rats by electrophysiology technique and immunohistochemistry, to investigate the effect and mechanisms of GAP-43 and VEGF in SCI.The main results of our research and discussion are as follows:1. changes of electrophysiogy in sciatic nerve in SCIWe investigate the change of threshold, amplitude and conduction velocity of action potential in sciatic nerve of the rats ofthe control group and the different time after SCI. The amplitude, threshold and conduction velocity of AP of the control group is 4.18±0.21mV, 0.296±0.009V and 20.60±1.55m/s, respectively. The increase of threshold, and the decrease of amplitude and conduction velocity of AP in sciatic nerve showed time-dependence change followed by 1d, 3d and 7d after SCI of rats, compared with the control group. However, the change of above indicants attenuated after 14d of rats SCI. This is the same to the results of the locomotion ability by CBS appraisal before. And these indicate that there are repair and regeneration after SCI and the recovery of locomotion ability.2. changes of GAP-43 Protein expression in the injury spinal cord tissue of rats GAP-43 is an important and decisive factor of repair and anagenesis. Theexpression of GAP-43 dicide the recovery of SCI. We study GAP-43 protein express in the injury spinal cord tissue after SCI of rats at the different time by immunohistochemistry. The number of GAP-43 of the control group is 2.53±0.77 in 200*field of vision. The peak is 16.33±2.96 in 200*field of vision on 7th d of SCI. but there were 9.47±1.83 on 14th d less than 7thd of SCI. Expression of GAP-43 proteins increased progressively followed by 1 d, 3d, and 7d after rat SCI, which reached the peak at the 7th d of SCI. These indicate that GAP-43 maybe promote the recovery of SCI.3.changes of VEGF Protein expression in the injury spinal cord tissue of rats Recently, it is reported that VEGF can protect spinal cord neurons, promote blood vascular endothelial cell growing, but also induce blood vessel developing. We study VEGF protein express in the injury spinal cord tissue after SCI of rats at the different time by immunohistochemistry.We found that there were expression of VEGF in two different neurons. We differentiate them by morphology:big motor neuron and glial cell. Expression of VEGF proteins increased obviously followed by 1d, 3d, and 7d on big motor neurons after rat SCI, comparing to the control group 0.60±0.89, which reached the peak 20.80±6.06 at the 3thd of SCI. And the expression reduced obviously at the 14th d of SCI, but there were no expression at the 28th d. These indicate that GAP-43 maybe promote the recovery of SCI. But there were expression of VEGF in glial cells at the 3th d, which reached the peak 35.83±6.11at the 14th d, lasting two weeks, and there were still expressing at the 28th d, but were less than the 14th d. The results indicate that VEGF expression depend on time, and maybe protect the neurons. But the expression in glial cell is late, because activiated cells can synthesize VEGF and protect neurons indirectly. There were expressions of VEGF in blood vascular endothelial cell. Expression of VEGF proteins increased progressively followed by 1d, 3d, 7d and 14d after rat SCI, but there was no expressiong on 28d. These indicate that VEGF maybe play part on blood vessel.Above all, there is repair and regeneration of injury nerve tissue, and GAP-43 and VEGF may be important. Changes of electrophysiology in sciatic nerve and GAP-43 and VEGF protein expression in the injury spinal cord tissue of rats can estimate the epair and regeneration of injury nerve tissue. Our study fulls up the mechanisms of pathology changes of SCI, also find the new index for estimating repair and regeneration of nerve.Conlusions:1. After SCI in rat, the excitability and the conductibility in sciatic nerve degrade. 2.GAP-43 protein in spinal cord expresses more strongly than the control group' s, and the expression depend on time in first and intermediate stage. 3. VEGF protein in blood vessel and nerve of spinal cord expresses more strongly than the control group' s, and the expression depend on time in first and intermediatestage.