蜗内直流电对耳蜗基底膜振动的影响

Effects of direct current on vibration of cochlear basilar membrane

目的 探讨外加直流电流后对耳蜗基底膜振动的影响。方法 在豚鼠耳蜗底回距圆窗龛缘 2 4mm处开一直径约 0 4mm小孔 ,作为测量活体基底膜的振动速度测试窗。在测试窗上、下缘的鼓阶、前庭阶各开一小孔 ,将铂 铱电极置入鼓阶、前庭阶作为跨蜗管的电刺激电极。用激光多普勒干涉测速仪观察直流电流对纯音诱发的基底膜振动速度的影响。结果 当外加电流前庭阶极性为正 ,鼓阶极性为负时 ,可以看到基底膜振动速度显著增大 ,给相反极性电流时 ,基底膜振动速度减小。结论 生理状态下的正内淋巴电位是耳蜗将声音能量转变为神经冲动的必要条件。适当提高外毛细胞顶端正电位 ,有助于提高耳蜗放大器的增益。外加负电位则严重影响耳蜗放大器的增益。

Objective To explore the effects of direct current on vibration of cochlear basilar membrane. Methods A small hole with a diameter about 0.4mm, which had the distance of 2.4mm from round window niche, was made on cochlear basic turn of guinea pig for measuring the velocity of basilar membrane in vivo. On the superior and inferior edge of the measuring window, holes were made on the scala tympani and scala vestibuli for insert stimulating electrode that was made of platinum-iridium. The basilar membrane vibration was elicited by tone and the effect of direct current stimuli were observed by Laser Doppler interference velocimeter . Results The velocity of basilar membrane vibration elicited with tone was increased significantly when positive current was delivered to scala vestibuli and the velocity was decreased on the contrary. Conclusion The positive endolymphatic potential is essential for cochlea to transit sound to nerve impulse in physiological condition. It is benefit to enhance the gain of cochlear amplifier when the positive potential is increased on the top of outer hair cells, but the extrinsic negative potential should significantly decrease the gain of cochlear amplifier.