中等强度噪声预暴露对强噪声致豚鼠听力损失恢复的影响

目的探索中等强度噪声预暴露对强噪声暴露后豚鼠听力损失恢复的影响。方法 30只豚鼠按数字表法随机分为5组：预暴露3 d组、预暴露2 d组、预暴露1 d组、强噪声暴露组、空白对照组（对照组）,每组6只。先将预暴露1 d组、预暴露2 d组、预暴露3 d组在90 dB SPL白噪声中暴露1、2、3 d,每天暴露3 h;再将上述3组和强噪声暴露组在110 dB SPL白噪声中暴露4 h。对照组不施加噪声暴露。噪声暴露前1 d、暴露后1、7 d检测听性脑干反应（ABR）。实验结束后测定血浆丙二醛（MDA）含量、超氧化物歧化酶（SOD）和总一氧化氮合酶（TNOS）活力。结果 （1）噪声暴露后1 d,预暴露3 d组、预暴露2 d组、预暴露1 d组、强噪声暴露组左右耳平均短声ABR阈值[分别为（44.58±3.42）、（53.34±8.35）、（49.17±5.57）、（46.67±7.48）dB]均升高,与对照组（23.75±2.26）dB相比差异均有统计学意义（P〈0.05）;暂时性听阈偏移（TTS）[分别为（20.83±4.69）、（27.92±7.53）、（20.42±5.42）、（21.67±6.15）dB]均增加,与对照组（-1.67±3.26）dB相比差异均有统计学意义（P〈0.05）。（2）噪声暴露后7 d,预暴露3 d组、预暴露2 d组、预暴露1 d组左右耳平均短声ABR阈值[分别为（27.50±2.61）、（26.67±3.26）、（27.50±2.61）dB]均降低,与强噪声暴露组（31.67±3.26）dB相比差异均有统计学意义（P〈0.05）;预暴露2 d组和预暴露1 d组永久性听阈偏移（PTS）[分别为（1.25±5.28）、（-1.25±3.11）]dB均降低,与强噪声暴露组（6.67±5.37）dB相比差异均有统计学意义（P〈0.05）;预暴露3 d组PTS有降低趋势。（3）各组高频ABR阈值变化不明显。（4）预暴露1 d组SOD活力[（105.74±13.21）U/ml]降低,与对照组（124.97±8.05）U/ml相比差异有统计学意义（P〈0.05）。预暴露3 d组和预暴露2 d组SOD活力[分别为（136.91±14.81）、（128.54±13.84）U/ml]均升高,与强噪声暴?

Effects of moderate intensity noise preconditioning on the recovery of hearing loss induced by high intensity noise in guinea pigs

Objective To investigate the effects of moderate intensity noise preconditioning on the recovery of hearing loss induced by high intensity noise in guinea pigs. Methods Thirty guinea pigs were randomly divided into 5 groups： the 3-day noise preconditioning group（ or the 3-day group）,the 2-day noise preconditioning group（ or the 2-day group）,the 1-day noise preconditioning group（ or the 1-day group）,the high intensity noise exposure group（ or the high intensity group） and the control group,each consisting of 6 animals. As a first step,the animals in the 3-day group,the 2-day group and the 1-day group were exposed to white noise of90 decibels sound pressure level（ dB SPL） respectively for 3 hours a day and for a succession of 3,2,1 days respectively（ 3h /day）.Then,the above 3 groups and the high intensity group were exposed to a traumatic white noise of 110 dB SPL for 4 hours. Guinea pigs in the control group were kept in a quiet environment. Auditory brainstem response（ ABR） was determined 1 day before exposure,and1 and 7 days after exposure. The content of malondialdehyde（ MDA） and the activities of superoxide dismutase（ SOD） and total nitricoxide synthase（ TNOS） were measured at the end of the experiment. Results（ 1） One day after exposure,click ABR threshold levels in the 3-day group,the 2-day group,the 1-day group and the high intensity group respectively increased to the levels of [（ 44. 58 ±3. 42）,（ 53. 34 ± 8. 35）,（ 49. 17 ± 5. 57） and（ 46. 67 ± 7. 48） dB],and statistical significance could be noticed,when compared with those of the control group（ P〈0. 05）. Temporary threshold shift（ TTS） all increased to the levels of [（ 20. 83 ± 4. 69）,（ 27. 92 ±7. 53）,（ 20. 42 ± 5. 42） and（ 21. 67 ± 6. 15） dB] and statistical significance could be noted,when compared with that [（- 1. 67 ±3. 26） dB]of the control group（ P〈0. 05）.（ 2） Seven days after exposure,click ABR threshold levels in the 3-day group,the 2-da