RESUMO
Noise has been a major problem to mankind and induces many auditory and extra-auditory hazards. This study was carried out to determine the injurious effects of noise on the hippocampus and to show whether Ginkgo biloba has any modulatory effect on hippocampal injury. Twenty-five adult male albino rats were divided into five groups: a control group; a noise group exposed to 100 dB of sound pressure level white noise 4h/day for 4 weeks; a protected group exposed to the same noise level with the administration of a G. biloba extract [50mg/kg daily] for 4 weeks; a recovery group, which was allowed to recover for 4 weeks after noise cessation; and a treated group, administered the same dose of G. biloba for 4 weeks after noise cessation. In the noise-exposed group, the pyramidal cell layer of CA1 and CA3 and the granular cell layer of the dentate gyrus [DG] showed a decrease in thickness compared with the control group, which showed loss and degeneration of many cells, and evidence of increased apoptosis. The protected and treated groups showed improvement in many parameters compared with the recovery group, that is, an increase in the thickness of CA1, CA3, and DG; increase in the surface area of cells; increased vascularity; and a statistically significant decrease in apoptosis compared with the recovery group. Noise exerted detrimental effects on cells of CA1, CA3, and DG of the hippocampus. Although partial spontaneous recovery may occur after cessation of noise exposure, the administration of G. biloba led to a marked decrease in the injurious effect of noise on the hippocampus. This might suggest the probable usefulness of G. biloba in reducing the central hazardous effects in individuals exposed to noise