الفهرس 
? Noise PollutionOnly 14 pages are availabe for public view
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Abstract
Background and aim of the study: Noise-induced hearing loss (NIHL), which is the second most common type of sensorineural hearing loss after presbycusis, is an irreversible disorder but potentially preventable. Noise induced hearing loss is a major health problem, because opportunities for overexposure abound, and exposures that damage hearing are not necessarily painful or even annoying. Extensive studies have documented the damaging effects of high-intensity acoustic overexposures on the cochlea, but only few works have focused on the danger of over exposure to moderate noise levels on the cochlea. Statins have recently been proposed to prevent NIHL so, this study was conducted to evaluate the effects of moderate intensity noise overexposure on the histological structure of the cochlea and to evaluate the possible protective role of Pravastatin.
Materials and Methods: Thirty adult male guinea pigs were included in the present study. Animals were divided into three groups: group I (control group) (12 animals), group II: 12 guinea pigs were further subdivided into two equal subgroups. Subgroup IIa animals were exposed to noise 70-90 decibels (dB) for 6hr/day for 6 weeks then sacrificed. Subgroup IIb were exposed to noise and given Pravastatin once daily for 6 weeks from the 1st day of exposure to noise then sacrificed. group III: recovery group (6 animals) were exposed to noise for 6 weeks then were left for spontaneous recovery for 4 weeks. The cochleae were dissected, decalcified and processed for histological and immune-histochemical study.
Results: Light and scanning electron microscopic examination of the cochleae revealed that noise exposure resulted in various degrees of damage of hair cells and their stereocilia, stria vascularis, cochlear nerve fibers and spiral ganglia. The spiral ganglia neurons showed increased
expression of Caspase 3. Administration of Pravastatin resulted in improvement of the structure of the cochlea compared to the exposed and the recovery groups. These results were confirmed by the morphometric and statistical results.
Conclusion: Exposure of guinea pigs to moderate intensity noise have irreversible damaging effects on the cochlear structure and concomitant administration of Pravastatin daily showed protective effects on these damaging effects.
Keywords: Noise induced hearing loss, Pravastatin, presbycusis, Caspase 3.