外源性谷氨酸对豚鼠耳蜗复合动作电位及微音电位的影响

EFFECT OF EXOGENOUS GLUTAMATE ON COMPOUND ACTION POTENTIAL (CAP) AND COCHLEAR MICROPHONICS (CM) OF GUINEA PIG′S COCHLEA

为观察和研究灌流外源性谷氨酸时复合动作电位 (CAP)和微音电位(CM)的变化特点 ,行全耳蜗灌流不同浓度谷氨酸 (1、5、10mmol/L) 2h,由圆窗记录CAP和CM。结果显示 :CAP的阈值变化与谷氨酸的灌流浓度有剂量依赖关系 ,灌流谷氨酸可以明显影响CAP的幅度和阈值 ,但对CM幅度及输入输出曲线的非线性特点没有显著的影响。研究表明谷氨酸对内毛细胞有选择性的作用 。

To investigate the changes in CAP and CM recorded from the cochlear round window when glutamate solution in different concentrations(10mmol/L, 5mmol/L, 1mmol/L) was instilled into whole cochlea perilymph. The results demonstrated that there was a dependent correlation between CAP threshold shift and glutamate concentration. CAP threshold shift and amplitude could be markedly influenced by glutamate instillation. However, amplitude of CM was not obviously affected, and the I/O function of CM amplitude always maintained a nonlinear characteristic. The results suggest that glutamate has selective effects between inner hair cells and outer hair cells. High concentration glutamate might cause an increase in intracellular calcium, even as high as to induce toxicity. It could be induced by glutamate when it acts on IHC′s presynaptic autoreceptor in positive feedback manner, or on the afferent neurons, so that the synapsis is directly damaged by glutamate concentration overload in synaptic cleft.