The protection of the retina from ischemic injury by the free radical scavenger EGb 761 and zinc in the cat retina.

We investigated the effects of a free radical scavenger (EGb 761) and zinc in experimentally induced ischemic injury in the cat retina. Total retinal ischemia for 90 min was produced in the left eyes of 40 cats by raising intraocular pressure. In group 1, 10 cats were used as control. The free radical scavenger (EGb 761, 100 mg/kg) in group 2 (10 cats) and zinc chloride (250 microg/kg) in group 3 (10 cats) were administered intravenously at the end of ischemia. In group 4, both EGb 761 (100 mg/kg) and zinc chloride (250 microg/kg) were injected into 10 cats. ERG and a histologic study were performed 1 h, 1 day, 3 days, 1 week and 2 weeks after ischemia. The amplitude of the ERG b-wave was 62.73+/-0.32, 84.31+/-6.10, 83.65+/-12.23 and 102.4+/-14.27%, and the summed amplitude of oscillatory potentials was 66.16+/-16.42, 99.44+/-14.92, 95.45+/-6.42 and 99.62+/-12.32% in each group 2 weeks after ischemia. There was no significant effect in animals that received zinc alone (group 3) by the end of 1 week but some additive effect in combining EGb 761 and zinc chloride (group 4) 1 h after ischemia. These findings suggest that the free radical scavenger EGb 761 may efficiently protect the retina from ischemic injury and zinc may have an additive effect when combined with a radical scavenger.