The Protection of the Retina from Ischemic Injury by the Free Radical Scavenger EGb 761 and Zinc in the Cat Retina

Abstract

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 μg/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 μg/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.

Expression of antioxidant enzymes in rat retinal ischemia followed by reperfusion

“…Previous studies have demonstrated an elevated presence of free radicals in ischemic/reperfused rat retina, either directly by electron paramagnetic resonance [28] or indirectly by showing diminished damage after administering antioxidant drugs such as SOD, EGB 761 extracted from Ginkgo biloba, vitamin E, mannitol, CAT, and several other compounds [2,29,30]. Several studies have demonstrated the ischemic effect on retina as…”

Clinical and electrophysiological efficacy of leaf extract of <i>Gingko biloba</i> L (Ginkgoaceae) in subjects with diabetic sensorimotor polyneuropathy

“…Daily dose of 120 mg of Ginkgo biloba was chosen based on information from prior clinical studies [23][24][25][26] suggesting a doseresponse relationship up to 240 mg [26]. Ginkgo biloba has been reported to protect various types of neurons in the central nervous system including cerebellum [27], cerebral cortex [28], basal ganglia [29], hippocampus [30] and retina [31] in various disorders like ischemia and oxidative stress.…”

Protecting retinal ganglion cells

“…A number of compounds targeting a variety of mechanisms including modulation of glutamate-induced excitotoxicity, [11][12][13][14] vascular regulation via inhibition of nitric oxide synthase 15,16 or the endothelin pathway, 17,18 oxidative stress, [19][20][21][22][23] and inhibition of glial activity 24,25 have been shown to be neuroprotective in animal models of glaucoma though few have been tested in formal clinical trials.…”