Histological and immunohistochemical study on the protective effect of Ginkgo biloba extract against glutamate-induced neurotoxicity in male albino rat retinal cells

ABSTRACT

Monosodium glutamate [MSG] has a flavor-enhancing effect; hence, it is added to processed food. It is known for its neurotoxicity. This study was conducted to demonstrate the possible protective effect of the natural antioxidant, Ginkgo biloba extract, against the neurotoxicity of MSG on the retinal cells of male albino rats. Thirty adult male albino rats were used. The animals were divided into the following groups group I was the control group and group II was subdivided into subgroup IIa, which received MSG injections for 7 days, and subgroup IIb, which received Ginkgo biloba [EGb 761] orally for 7 days and then received MSG injections, in addition to EGb. Retinal sections were stained with H and E stain, toluidine blue stain, and immunohistochemical staining for glial fibrillary acidic protein [GFAP]. Total retinal thickness, thickness of the outer nuclear layer, and the mean area% of GFAP were measured using an image analyzer. MSG caused complete loss of the outer and inner segments of the photoreceptors, a decrease in the thickness of the outer nuclear and plexiform layers, focal cytoplasmic vacuolation in the inner nuclear layer, and complete distortion of the ganglion cell layer. Such abnormalities were, to a large extent, prevented with the use of EGb 761. Statistically significant differences in the total retinal thickness, the thickness of the outer nuclear layer, and mean area% of GAP were found between the groups. MSG exposure was shown to induce deleterious morphological changes on the retina, many of which were prevented with the use of EGb 761. Thus, this natural extract could have further clinical implications in reducing glutamate-induced excitotoxicity in several ophthalmic diseases