The Study Of The Effect Of Glutamate And Memantine On The Retinal Ganglion Cells After Blast Injury Combined With Hypoxia In Rats

Background and Aims: The occurance of apoptosis of the RGCs in glaucoma, diabetic retinopathy, eye explosive injury and optic nerve semitransection injury has been shown in many investigation. Furthermore it has been certified that the exitotoxitity of glutamate is the important factor which trigger the apoptosis cascade reaction while ischemia and hypoxia. It is reported that memantine the NMDA receptor antagonist can reduce the apoptosis of the RGCs in glaucoma and optic nerve semitransection injury. Till now it is not reported whether the apoptosis of the RGCs mediated by glutamate exists in the visual disfunction after blast injury and whether Memantine has effect on the RGCs after blast injury. The aim of the study is to observe the pathomorphologic characteristics of the eye, the concentration of glutamate in the retina, the expression of caspase-3, the apoptosis of RGCs and the effect of Memantine on the RGCs after blast injury and blast injury combined with hypoxia, to approach the causative mechanism of injury of ocular blast injury, and to provide theoretical guide for the treatment after blast injury combined with hypoxia.Methods: 80 Wistar rats were divided into four groups randomly: normal group (NG) , blast injury group (BG), hypoxia control group (HCG) , and hypoxia treat group(HTG). The rats of NG is in no dispose. The injuried rats were inflicted of blast injury by BST- I bio-shock tube (the overpressure peak 482.7±1.2kPa, positive pressure time 43.6ms) . Rats of HCG, HTG were put into the 12.5% hypoxic-cabin for 6 hours immediately after they were inflicted of blast injury, and the rats of HCG were intraperitoneal injection with saline 4ml/kg.d, the rats of the HTG were intraperitoneal injection with memantine 10mg/kg.d . At days 1, 3 , 5 , 7 the injuried rats were killed to gain the retina to observe the pathomorphology characteristics of the eye, the concentration of glutamate in the retina, the expression of caspase-3, the apoptosis of RGCs.Results:1.characteristics of the injury: 1.1 the total condition: Some rats of BG behaviours dysphoria, quic anapnea, the mortality is approximately 4 percent. Some rats of HCG present cyanosis, dysphoria, even downcast, reaction dullness, the mortality is approximately 20 percent. 1.2 ocular condition: 1.2.1 the light microscope: corneal epithelium and hypothallus slightly edema, the blood vessel of ciliary body slightly dilataltion, the occurrenc of effusion of anterior chamber; the blood vessel of choroids and retina slightly dilatation, hemocyte stasis, occasionally the outer segment of photoreceptor cell constitution derangement, the cells of inner nuclear layer and RGCs vacuoles alteration, and the nervr fiber layer presents edema. 1.2.2 the transmisson electron microscope: the blood vessel endothelial cell slightly swelling, the membranous disc lamellose of the photoreceptor is in disorganization, inner and outer nuclear layer and RGCs exist edema, mitochondria swell, endoplasmic reticulum distension, neurites degenerate and myelin sheaths come into being.2. The concentration of glutamate in the retina: The concentration of glutamate in the uninjuried retina is 0.245±0.008 ug/mg, it rises significantly at 1 day after injury (P<0.01), it falls gradually afterward, but remains upper than the normal (Z^O.Ol) .At day 1 to 5, The concentration of glutamate in the reinta in HCG is upper than the BG(P<0.05), while the concentration of glutamate in the reinta in HTG is lower than the HCG at day 1,3 and 7CPO.05).3. The immunohistochemistry staining of the Caspase-3P20: The positive cells of Caspase-3P20 are principle RGCs. The positive cells Caspase-3 P20 are not detected in the NG. It start to a occurrenc at day 3 after injury in BG and HCG, increase strikingly at day 5 (PO.01), and remains the leavel at day 7. It also start to a occurrenc at day 3 after injury in HTG, and remains positive expression at day 5 and 7. At eyery corresponding time the positive expression in HCG is upper than it in BG(P<0.0l),while the positive expression in HTG is lower than it in HCG. (PO.01).4. TUNEL staining : The positive cells of TUNEL staining are principle RGCs. The positive cells TUNEL staining are not detected in the NG. It start to a occurrenc at day 3 after injury in BG and HCG, increase strikingly at day 5 (P<0.01), and remains the leavel at day 7. It also start to a occurrenc at day 3 after injury in HTG, and remains positiveexpression at day 5 and 7. At eyery corresponding time the positive expression in HCG is upper than it in BG (P<0.01),while the positive expression in HTG is lower than in HCG.5. The analysis of correlation: The result show that the analysis of correlation between the concentration of glutamate in the retina, the immunohistochemistry staining of the Caspase3P20 of RGCs and TUNEL staining: R2 > 0.8, PO.01.Conclusion:1. Blast injury can lead to the destruction of the blood-aqueous barrier, the disturbance of the circulation of uvea and retina, the lesion of photoreceptor cell ,the degeneration of RGCs and neurite.2. The concentration of glutamate in the injuried retina rises to the peak at 1 day. The result manifests that the exitotoxicity mechanism of glutamate is switched on in earlier period after blast injury.3. The high positive expression of Caspase3 P20 is detected in the injured RGCs. It shows that the activation of the apoptic gene Caspase3 maybe is in relation to the apoptosis of RGCs.4. The positive TUNEL staining RGCs are detected in the injured retina. It shows that the apoptosis of RGCs mediated by glutamate maybe an important agent in the retina lesion after blast injury.5. The total condition , the ocular pathomorphology, the concentration of glutamate in the retina , the positive expression of Caspase3 P20 and the the positive TUNEL staining RGCs are much more serious in HCG than in BG. It manifests that hypoxia can worsen the coup condition.6. The concentration of glutamate in the retina , the positive expression of Caspase3 P20 and the the positive TUNEL staining RGCs are much more slightly in HTG than in HCG. It shows that memantine can play a key role in protecting the RGCs after blast injury.