Protection of the rat retinal ganglion cells from ischemia-reperfusion injury by Ginkgo biloba

Abstract

Ischemic-reperfusion injury causes extensive loss of retinal ganglion cells (RGC). We studied the effects of single and combined extracts of Ginkgo biloba (GB), Hypericum perforatum (HP) and Panax quinquefolis L. (PQ) on RGC survival after transient retinal ischemia-reperfusion damage in albino Lewis rats. Ischemic-reperfusion injury was induced in the retina by insertion of a needle into the anterior chamber of the eye. The needle, attached to a saline tube, delivered a pressure of 110 mm Hg for 60 min. Animals were given oral administration of single or combined extracts daily for 14 days beginning immediately after ischemic-reperfusion. There were five treatment groups: GB (30mg/day), HP (84mg/day), PQ (84mg/day), Menta-Fx (an extract containing 7.7% GB, 61.5% HP and 30.8% PQ) (84mg/day) and control (PBS, 0.01M). Seven days after injury a piece of gelfoam soaked with 6% Fluoro-Gold was placed on the surface of both superior colliculi to retrogradely label surviving RGC in the damaged eye and normal RGC in the undamaged eye. At the end of the treatment period animals were sacrificed and retinas of both eyes removed and wholemounted. Changes in the numbers of RGC in each animal were expressed as a ratio of surviving RGC in damaged eye/RGC in undamaged eye in the same animal. There was no significant effect in RGC survival in animals that received HP, PQ and Menta-Fx. Treatment with GB however significantly increased RGC survival after ischemic-reperfusion injury. A greater survival effect was observed in the peripheral retina where the extent of RGC survival was 2.3 fold compared to 1.7 fold in the central retina. Supported by Research grant from the University of Hong Kong