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H Katano, Y Kawai, A Tamai, Y Inoue; Changes In The Electroretinogram During Ischemia-reperfusion In Normothermic And Hypothermic Rats . Invest. Ophthalmol. Vis. Sci. 2002;43(13):1786.
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Purpose: The present study was designed to examine the changes in the electroretinogram (ERGs) during postischemic reperfusion in young (4 months old) and aged (over 18 months old) Wistar rats under normothermic and hypothermic conditions. Methods: The ERG responses to single white light flashes were recorded by Ag/AgCl electrodes placed on the cornea. Ocular ischemia was induced by the elevation of intraocular pressure (IOP) from 15 mmHg to 80 mmHg for 2 hours. In the hypothermia groups, the rectal temperature was decreased from 38.5 °C to 31.5 °C by using a domestic cooling pad throughout the experiments. Results: Exposure to 80 mmHg of IOP decreased the choroidal blood flow to 40 - 60% of the baseline value. In the young rats, the normalized amplitude of b-wave decreased during ischemia to 60.6±3.0% of the baseline value under normothermic condition and to 70.8±5.3% under hypothermic condition. During reperfusion, the amplitude of the b-wave recovered to the baseline level by 2 hours under normothermic condition, and 1 hour under hypothermic condition. In the aged rats, exposure to ischemia decreased the amplitude of b-wave to 38.9±5.0% under normothermic condition and to 55.3±7.1% under hypothermic condition. In the aged rats, however, it did not recover to the baseline level within 6 hours during reperfuisoin under normothermic condition, on the other hand, it recovered by 4 hours under hypothermic condition. Conclusion: These results indicate that the electrophysiological function of the retina is less tolerable against ischemia-reperfusion in aged rats than in young rats. Hypothermia plays a beneficial role in protecting the retinal function during ischemia-reperfusion in young and aged rats.
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