Protective Effect Of Melatonin Against Rat Retinal Ischemia Reperfusion Injury

Objective To investigate the protective effect of melatonin on retinal ischemia reperfusion injury and its possible mechanism .Methods 136 Wistar rats were randomly divide into control group, model group, protective group. Retinal ischemic reperfusion was induced in rat by acute elevated intraocular pressure through normal saline intracameral perfusion. The rats in the protective group received four subcutaneous injections at six-hour intervals for total dosage of of 10mg/kg melatonin. The first dose of melatonin was administered 5 minutes before retinal ischemia, the rats in the control group and the molel group received a subcutaneous injection of vehicle( control 2% alcohol ) at same dose .The eyes were enucleated at 0, 6, 12, 24, 48hours and 3days and 7days after reperfusion. Histopathologic changes were observed with light microscopy and the thickness of inner retinal layers were measured. The contents of malondialdehyde ( MDA ), superoxide dismutase ( SOD ), and nitric oxide ( NO ) in the retinal were measured by photometry. These were compared with equivalent measurements of the control.Results 1. In the model group, we can found edema of retinal (especially in the neuron fibrary layer and inner plexiform layer) in the early stage after ischemia-reperfusion injury, and the retinal atrophy, degeneration and necrosis were found in the later period. We can found that the thickness of inner retinal layers became thinner and the RGCs was much less than the control group. In the protective group, the edema was much less than model group in the early stage and the thickness of inner retinal layers were more than the models group in the later period. 2. after ischemia-reperfusion , the content of MDA and NO were increased and activity ofSOD is decrease dpersistently, which' significantly differed from the control group(P<0.01). In contrast to the model group, the content of MDA and NO in the protective group were reduced (P<0.01), and activity of SOD is increased (P<0.01). Conclusion Melatonin, by inhibiting production of NO and elevating the ability of anti-oxidation in rat retina, can protect retinal neurons from ischemia-reperfused injury.