The Studies On Retinal Injury Induced By Glutamate Intravitreal Injections And Protection Of Extracts Ginkgo Biloba On It

Objective To study injuries of retinal nerve cell and the changes of nitric oxide and hydroxyl free radical in the retinal neurotoxicity models induced by Glutamate intravitreal injections in adult rabbits and the acute ocular hypertension model established by saline perfused in anterior chamber of rabbit eyes and the effects of extracts ginkgo biloba (EGB) on it.Methods 1.Changes of ERG at various concentrations of glutamate at different time were observed in the retinal neurotoxicity models induced by Glutamate intravitreal injections in adult rabbits .EGB was retrobulbarly injected in the models. The levels of NO were measured by spectrophotometer. Retina DNA fragmentation was determined by agarose gel eletrophoresis. 2. A model of ocular hypertension was established by perfusing physiological saline in anterior chamber, rabbits were simultaneously injected intravenously with ginkgo flavonoids and after 70 hours were injected intravenously with sodium salicylate that by acting as an hydroxyl-99radical trap, forms 2,3-dihydroxybenzoic acid (2,3-DHBA). 2,3-DHBA were identified by highpower liquid chromatography coupled to electrochemical and fluorescent detectors (HPLC-ECD). salicylate was quantitated fluorimetrically.Results: l.The b and OPs wave amplitudes of dark adaptation ERG were significantly reduced and gradually recovered when the dosage of glutamate was 100ng/20lil. But it didn't recovered within 7 days when received more than 300pg/20pl. There were significant changes of ERG when compared big dosage group with small dosage group or control group received PBS. The group received 600iig/20|il dosage glutamate and 40(ig/20iJl MK-801 (NMDA receptor antagonist) did not show these changes.2. The levels of NO in retina in experiment groups was significantly increased compared to controls, after treatment with high dosage of EGB, levels of NO was decreased to normal. It was not decreased by injection small dosage of EGB.DNA fragmentation of retina apoptosis was detected in experiment groups and small dosage EGB groups.3. After 5 hours ocular hypertension and recovering till 72 hours. The levels of hydroxyl radicals in rabbit retina in model groups were significantly higher than that in the control groups. After treatment of ginkgo fiavonoids, the levels of hydroxyl radicals in rabbit retina in middle dosage of ginkgo fiavonoids groups or above were significantly decreased compared to the model groups. But the levels of hydroxyl radicals in rabbit retina in small dosage of ginkgo fiavonoids groups are not decreased-9 -compared to model groups.Conclusion l.More than 1 OOlij dosage of glutamate in intravitreal injections at adult rabbit can induce function changes of rabbit retina. There were significant excitotoxicity on rabbit retina when dosage were more than 300|ig. NMDA receptor antagonist MK-801 can protect against glutamate-induced excitotoxcity. 2. The retina apoptosis was induced by glutamate by intravitreal injection in adult rabbit and was inhibited by EGB that may be through blocking the generation of NO free radicals.3. ginkgo flavonoids as free radical scavenger may antagonize hydroxyl radicals damage in the rabbits retina undergoing acute ocular hypertension status and protect the retinal tissue following acute ocular hypertension status...