Experimental Studies on mechanism underlying noise-induced Rearing disorder.

第一年分别测定两种音调刺激下耳蜗微音（CM）和听神经复合动作电位（CAP）在100dB声压下4kHz纯音暴露10min前后的变化。CM （CM- dp）中2f1-f2失真产物的输出在曝光后立即显著降低，然后逐渐恢复。CM-DPs的减少和恢复与cap的减少和恢复密切相关，这可能表明外毛细胞（OHC）功能的影响在噪声诱导的暂时阈值移位的发生中起重要作用。在随后的研究中，已知水杨酸会干扰ohc的机电转导（EMT），揭示了声音暴露对CM-DPs的不同改变。从这些结果可以推测声过度刺激会影响热盐的机电转导。在接下来的一年里，研究了响亮的声音和水杨酸盐的联合作用。通过改变两种药剂的使用顺序，效果发生了改变。现有的声音引起的损伤减弱了水杨酸盐的额外耳毒性，而当水杨酸盐在声音暴露之前施用时，则不会发生衰减。从这些结果可以推测MET在耳蜗转导机制中比EMT占据主导地位。在不接触任何声音或药物的情况下，意外地记录了几种动物耳蜗的自发电振荡（交流电位）。对交流电位特性的密切观察表明，这些电位是由主动机械振动系统在基底膜上的特征频率与电位对应的区域产生的。

In the first year, cochlear microphonics (CM) in response to two tone stimuli as well as compound action potential (CAP) of the acoustic nerve were measured before and after exposure to 4kHz pure tone at 100dB SPL for 10min. The output of 2f1-f2 distortion product in the CM (CM-DP) were markedly reduced immediately after the exposure and then recovered gradually. The reduction and recovery in CM-DPs closely paralleled with those in the CAP.This may indicate that the affection of the outer hair cell (OHC) function plays an important role in developing the noise induced temporary threshold shift. The following study with administration of salicylate, which was known to interfere the electro-mechanical transduction (EMT) of OHCs, reveled the different alterations of the CM-DPs from those with sound exposure. From these results it is postulated that acoustic overstimulation affects the mechano-electrical transduction (MET) of OHC.In the following year, combined effects of loud sound and salicylate were studied. The effects were altered by changing the order in which the two agents were applied. The existing sound-induced damage attenuated the additional ototoxicity of salicylate, whereas attenuation did not occur when salicylate administration preceded sound exposure. From these results it is postulated that the MET holds dominant position over EMT in the cochlear transduction mechanism.Spontaneous electrical oscillations (AC potentials) were accidentally recorded from the cochlea of several animals without any exposure to sound or drugs. Close observations in the properties of the AC potentials indicated that the potentials were generated by the active mechanical vibration system at the area on the basilar membrane where the characteristic frequency corresponded to that of the potential.