强声暴露后豚鼠耳蜗外毛细胞电反应特性的在体研究

Response Characteristics of the Guinea-pig Cochlea Outer Hair Cells and Its Alteration Induced by Intense Tones: Intracellular studies

目的 探讨强声暴露后豚鼠耳蜗毛细胞感受器电位 (receptorpotential,RP)变化和复合神经动作电位(compoundactionpotential,CAP)的关系。方法 在成功建立豚鼠耳蜗毛细胞电反应记录方法后 ,将同一强度、不同频率的强声施加于受试耳 ,观察外毛细胞频率响应和RP及圆窗CAP的变化。结果 外毛细胞在不同频率强声暴露后 ,特征频率 (characteristicfrequency ,CF)的RP反应幅度减小 ,刺激声强度与RP的I-O曲线线性增加 ,CF的频率选择性下降。频率低于CF的强声较高于CF的强声更易引起CF的RP下降。重复暴露有累加效应。同步记录的圆窗CAP未见阈移。结论 低频强声引起耳蜗外毛细胞RP损伤也遵循半倍频程漂移规律。

Objective To study the response characteristics of the hair cel1 receptor potentials(RP) and the changes both in the receptor potential of outer hair cells (OHCs) and the compound action potential(CAP) following rather 1ow-frequency loud tones exposure. Methods Intracellular recordings were made on cells of the organ of Corti from the low-frequency region (third turn) of the guinea pig cochlea, the recording sites being confirmed by subsequent histology. Response characteristics of the hair cell receptor potentials and the changes both in the receptor potential of OHCs and CAP following rather low-frequency loud tones exposure were studied.Results Following multiple loud tones (125 dB SPL, 250 ms) exposure, OHCs demonstrated a cumulative decrease in their voltage responses to a test tone, where as CAP showed no threshold shift.Conclusion The largest decreases in sensitivity of OHCs and nonlinear properties reduction were found at the characteristic frequency (CF) after intense tones below their CF exposure.