外耳道间断加压对豚鼠耳蜗外侧壁心钠素表达的影响

Effects of Intermittent Overpressure in Ear Canal on Expression of ANP in Cochlear Lateral Wall of Guinea Pigs

目的 研究外耳道 49和 2 0cmH2 O间断加压对豚鼠听功能及耳蜗外侧壁心钠素 (ANP)表达的影响。方法 建立豚鼠外耳道间断加压模型 ,观察 49和 2 0cmH2 O压力引起的中、内耳病理改变及AEP阈值改变 ,用免疫组化SP法研究心钠素在耳蜗外侧壁的表达。结果 49cmH2 O间断加压引起鼓膜松驰部和中耳粘膜出血 ,各频率反应阈平均提高 12 0 9dB ;2 0cmH2 O间断加压对中耳及内耳均无明显损伤 ,不影响AEP阈值 ;间断加压使ANP在耳蜗外侧壁表达减弱。结论 2 0cmH2 O的压力相对安全 ,可以此为参考进行外耳道加压实验。

Objective To investigate the effects of intermittent overpressure in ear canal on the expression of atrial natriuretic peptide (ANP) in the cochlear lateral wall of guinea pigs.Methods Intermittent pressure increase of 49 cmH 2O and 20 cmH 2O was respectively loaded in ear canal of normal guinea pigs in an experimental model.The expression of ANP was investigated by immunohistochemical SP method.Histopathological changes of middle and inner ear were examined under light microscope.AEPs were recorded using tone-burst at 0.5,1.0,4.0,and 8.0 kHz.Results Intermittent pressure increase of 49 cmH 2O may damage middle ear,inducing an average of 12.09 dB threshold increase across the frequencies.The most common change was tympanic relaxation.In some cases,small hemorrhages in the tympanic membrane and /or in the otic bulla were observed.There was no sign of hair cell loss across the cochlear turns.Application of 20 cmH 2O caused no obvious pathophysiological change in each ear. Expression for ANP decreased in the cochlear lateral wall of ears with pressure treatment,suggesting that ANP positive cells had a paracrine and/or autocrine function in the organ.ANP may play a role in the local control of fluid and electrolyte homeostasis of the inner ear.Conclusion Intermittent overpressure of 20 cmH 2O is safe in this experiment,which may serve as a reference in further studies.ANP positive cells in the cochlear lateral wall have an autocrine/paracrine function.