Sellick P M, Kirk D L, Patuzzi R, Robertson D
The Auditory Laboratory, Discipline of Physiology, School of Biomedical, Biomolecular and Chemical Sciences, The University of Western Australia, Nedlands, WA 6009, Australia.
Hear Res. 2007 Feb;224(1-2):84-92. doi: 10.1016/j.heares.2006.11.011. Epub 2007 Jan 12.
The calcium chelator BAPTA was iontophoresed into the scala media of the second turn of the guinea pig cochlea. This produced a reduction in low frequency cochlear microphonic (CM) measured in scala media and an elevation of the cochlear action potential (CAP) threshold that lasted for the duration of the experiment. Using two pipettes, one filled with KCl and the other KCl and BAPTA (50, 20 and 5 mM) it was possible to observe the effect of passing current through one electrode while measuring the endolymphatic potential (EP) with the other. The results demonstrated that current passed via the BAPTA pipette caused a sustained increase in EP of 8.2, 12.9 and 7.8 mV in the three animals used. This increase coincided with the decrease in low frequency CM that indicated a causal connection between the two. In a second series of experiments, pipettes with larger tips were inserted into scala media in the first cochlear turn and BAPTA was allowed to diffuse from the pipette. The results confirmed the relationship between EP increase and the fall of scala media CM. One interpretation of these results is that lowering the Ca2+ concentration of endolymph with BAPTA inhibits mechano-electrical transduction in outer hair cells (OHCs) and leaves the hair cell transduction channels in a closed state, thus increasing the resistance across OHCs and increasing the EP. These findings are consistent with a model of hair cell transduction in which tension on stereo cilia opens the transduction channels.
将钙螯合剂1,2-双（2-氨基苯氧基）乙烷-N,N,N',N'-四乙酸（BAPTA）通过离子电渗法导入豚鼠耳蜗第二圈的中阶。这导致中阶测量的低频耳蜗微音器电位（CM）降低，以及耳蜗动作电位（CAP）阈值升高，且这种情况在实验持续期间一直存在。使用两根移液管，一根装有氯化钾，另一根装有氯化钾和BAPTA（50、20和5 mM），可以在通过一个电极通电流的同时，用另一个电极测量内淋巴电位（EP），从而观察其效果。结果表明，通过装有BAPTA的移液管通电流，在所用的三只动物中，EP持续增加了8.2、12.9和7.8 mV。这种增加与低频CM的降低同时出现，表明两者之间存在因果关系。在第二系列实验中，将尖端较大的移液管插入耳蜗第一圈的中阶，使BAPTA从移液管中扩散。结果证实了EP增加与中阶CM下降之间的关系。这些结果的一种解释是，用BAPTA降低内淋巴中的Ca2+浓度会抑制外毛细胞（OHC）中的机械电转导，并使毛细胞转导通道处于关闭状态，从而增加跨OHC的电阻并提高EP。这些发现与一种毛细胞转导模型一致，在该模型中，静纤毛上的张力会打开转导通道。
