Kirk D L, Moleirinho A, Patuzzi R B
Physiology Department, University of Western Australia, Nedlands.
Hear Res. 1997 Oct;112(1-2):69-86. doi: 10.1016/s0378-5955(97)00104-4.
Neural auditory thresholds in the guinea pig can be temporarily improved by up to 6 dB about 2 min after the cessation of an moderately intense low-frequency tone (Kirk and Patuzzi, 1997). We have measured changes in the f2-f1 distortion product otoacoustic emission (DPOAE) and low-frequency microphonic potential in scala tympani before, during and after a low-frequency tone (200 Hz) to determine the cause of this so-called bounce phenomenon. In particular we have analysed the low-frequency microphonic waveform in detail to estimate changes in the maximal receptor current through the outer hair cells (OHCs), the sensitivity of the OHC forward transduction process and the change in OHC operating point on the mechano-electrical transduction transfer curve. Our results indicate that a 200 Hz tone changes the maximal current and sensitivity of the OHCs minimally, but more importantly, it transiently changes the operating point on the OHC transfer curve. In particular, the operating point changes are consistent with a movement of the OHC stereocilia away from the OHC basal body at the peak of the bounce. These changes detected using the microphonic potential are associated with changes in the level of the f2-f1 DPOAE that correlate well with the electrical measurements. We suggest that the shift in operating point is largely responsible for the increase in cochlear sensitivity, and is due to a disruption of the salt balance within the cochlea during the intense low-frequency tone.
在豚鼠中，适度强度的低频音调停止后约2分钟，神经听觉阈值可暂时提高多达6分贝（Kirk和Patuzzi，1997）。我们测量了低频音调（200赫兹）之前、期间和之后鼓阶中f2 - f1畸变产物耳声发射（DPOAE）和低频微音器电位的变化，以确定这种所谓反弹现象的原因。特别是，我们详细分析了低频微音器波形，以估计通过外毛细胞（OHC）的最大受体电流变化、OHC正向转导过程的敏感性以及OHC在机电转导传递曲线上工作点的变化。我们的结果表明，200赫兹的音调对OHC的最大电流和敏感性影响最小，但更重要的是，它会短暂改变OHC传递曲线上的工作点。特别是，工作点的变化与反弹峰值时OHC静纤毛远离OHC基体的运动一致。使用微音器电位检测到的这些变化与f2 - f1 DPOAE水平的变化相关，这些变化与电学测量结果密切相关。我们认为，工作点的移动在很大程度上导致了耳蜗敏感性的增加，这是由于在强烈低频音调期间耳蜗内盐平衡的破坏所致。
