EVALUATION OF RAT MODEL OF CHRONIC GLAUCOMA BY LIGATING EPISCLERAL VEINS

Objective To develop and evaluate the rat model of chronic glaucoma by episcleral veins ligation （EVL）. Methods Experimental glaucoma was induced unilaterally in 28 male Sprague-Dawley rats by ligating two episcleral veins. Intraocular pressure （10P） in rats was measured by a Goldmann applanation tonometer under 3 % pentobarbital sodium anesthesia. The optic nerve head and retinal vasculature were assessed by repeated fundus examinations. The amount of optic nerve axons was assessed by Image-Pro Plus image analysis system in a masked fashion. Results lOP without EVL was （ 19.21 ± 1.23） mmHg, whereas the EVL eyes gained about 1.8-fold higher 10P[ （33.96 ±2. 73） mmHg]after EVL immediately （ P 〈 0. 001 ）. The elevated IOP gradually decreased over time. However, the differences were kept significant up to 8 weeks after EVL. The lOP was reduced to similar levels as contralateral eyes at 12 and 16 weeks after EVL. The glaucomatous optic nerve excavation appeared in EVL eyes at 8 weeks after EVL, and the optic nerve excavation enlarged gradually with the increasing post-operation time. The amount of optic nerve axons also significantly decreased in EVL eyes at 8 weeks after EVL, and the amount of axons decreased gradually with the increasing post-operation time. Conclusion Increase of lOP caused by EVL represents a useful and efficient model of experimental glaucoma in rats.

Exploration of the glutamate-mediated retinal excitotoxic damage: a rat model of retinal neurodegeneration

AIM： To explore the more suitable concentration of glutamate or N-methyl-D-aspartic acid（NMDA） for intravitreal injection to establish a rat model of retinal neurodegeneration. METHODS： We injected different doses of glutamate（20 or 50 nmol） or NMDA（40 nmol） into the vitreous chambers of rats, then measured the concentration of glutamate and retinal thickness, quantified apoptotic cells and determined the degree of tau hyperphosphorylation at different time points. T-test was used for comparison of two groups. One-way ANOVA and Turkey＇s multiple comparisons test were used for comparisons of different groups, and P values below 0.05 were considered statistically significant.RESULTS： The glutamate level in the rats treated with 50 nmol of glutamate was twice that of the control group and persisted two weeks. Seven days after intravitreal injection of 50 nmol of glutamate, three parameters [inner retinal thickness（IRT）, retinal thickness（RT） and ganglion cell layer（GCL） cell number] were reduced significantly. Furthermore, numerous TUNEL-positive cells were observed in the GCL one day after intravitreal injection of 50 nmol of glutamate, the expression of the apoptosisrelated factor cleaved casepase-3 was markedly increased compared with the expression levels in the other treatment groups, and the expression levels of tau s396 and tau s404 were significantly increased compared with those in the control group.CONCLUSION： This study demonstrates that the intravitreal injection of 50 nmol of glutamate can establish the more effective retinal neurodegeneration animal model relative to other treatment groups.