Objective To investigate the protective effect of moderate noisy backgrounds on guinea pig's hearing after an exposure to a traumatic noise. Methods Thirty guinea pigs were randomly divided into five groups (6 each). Animals in group A, B, C and D were subjected to noise of 84 decibels sound pressure level (dB SPL) for 4, 8, 24 and 0 hour respectively after a traumatic exposure of 110 dB SPL, and those in group E were kept in quiet environment. Distortion product oto-acoustic emission (DPOAE) amplitudes were determined on 1 day prior, and 1 and 7 days after noise exposure. Blood plasma was obtained to determine the contents of malondialdehyde (MDA) and the activities of hemocuprein (SOD) and nitricoxide synthase (NOS) at the end of the experiment. Results Noise-induced hearing loss was caused in group D after a traumatic exposure. At the 1st and 7th day after exposure, DPOAE amplitudes were higher in group A and B than in group D, especially at high frequencies, while no significant difference was observed between group C and D. At the 7th day after exposure, the activity of SOD lowered, while the content of MDA increased in group A and B as compared with group E (P<0.05). The content of MDA in group A increased as compared with group D (P<0.05). Conclusion After the traumatic noise-exposure, the recovery of noise-induced hearing loss, especially the high-frequency hearing loss could be motivated when exposed to noise at 84 dB SPL for 4 or 8 hours.%目的 探讨强噪声暴露后中等水平噪声环境对豚鼠听力的保护作用.方法 30只雄性健康白化种红目豚鼠随机分为5组,每组6只.A、B、C和D组分别于110dB SPL白噪声暴露4h后继续84dB SPL噪声暴露4、8、24、0h;E组为空白对照,不施加噪声暴露.噪声暴露前1d、暴露后1d和7d进行3次畸变产物耳声发射(DPOAE)测定.测试完毕后,取血浆测试超氧化物歧化酶(SOD)、丙二醛(MDA)含量及一氧化氮合酶(NOS)活力.结果 强噪声暴露后,D组豚鼠出现噪声性听力损失.噪声暴露后1d和7d,A、B两组DPOAE幅值较D组升高,尤其表现在高频部分,而C组与D组比较差异无统计学意义.噪声暴露后7d,与E组相比,A、B两组SOD活力降低、MDA含量增加(P＜0.05).与D组相比,A组MDA含量增加(P＜0.05).结论 强噪声暴露后,84dB、4h和84dB、8h的声环境可促进噪声性听力损失的恢复,尤其是高频听力损失.
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