Department of Otorhinolaryngology, Peking University Third Hospital, Beijing 100083, P. R. China.
Anal Chem. 2012 Jun 19;84(12):5433-8. doi: 10.1021/ac301087v. Epub 2012 Jun 6.
As one of the most important neurochemicals in biological systems, ascorbate plays vital roles in many physiological and pathological processes. In order to understand the roles of ascorbate in the pathological process of tinnitus, this study demonstrates an in vivo method for real time monitoring of the changes of ascorbate level in the cochlear perilymph of guinea pigs during the acute period of tinnitus induced by local microinfusion of salicylate with carbon fiber microelectrodes (CFMEs) modified with multiwalled carbon nanotubes (MWNTs). To accomplish in vivo electrochemical monitoring of ascorbate in the microenvironment of the cochlear perilymph, the MWNT-modified CFME is used as working electrode, a microsized Ag/AgCl is used as reference electrode, and Pt wire is used as counter electrode. Three electrodes are combined together around a capillary to form integrated capillary-electrodes. The integrated capillary-electrode is carefully implanted into the cochlear perilymph of guinea pigs and used both for externally microinfusing of salicylate into the cochlear perilymph and for real time monitoring of the change of ascorbate levels. The in vivo voltammetric method based on the integrated capillary-electrodes possesses a high selectivity and a good linearity for ascorbate determination in the cochlear perilymph of guinea pigs. With such a method, the basal level of cochlear perilymph ascorbate is determined to be 45.0 ± 5.1 μM (n = 6). The microinfusion of 10 mM salicylate (1 μL/min, 5 min) into the cochlear decreases the ascorbate level to 28 ± 10% of the basal level (n = 6) with a statistical significance (P < 0.05), implying that the decrease in ascorbate level in the cochlear may be associated with salicylate-induced tinnitus. This study essentially offers a new method for in vivo monitoring of the cochlear perilymph ascorbate following the salicylate-induced tinnitus and can thus be useful for investigation on chemical essences involved in tinnitus.
作为生物系统中最重要的神经化学物质之一，抗坏血酸在许多生理和病理过程中发挥着至关重要的作用。为了了解抗坏血酸在水杨酸盐诱导的耳鸣病理过程中的作用，本研究采用碳纤维微电极（CFMEs）修饰的多壁碳纳米管（MWNTs），通过体内实时监测水杨酸盐局部微灌注诱导的豚鼠耳蜗外淋巴中抗坏血酸水平的变化，展示了一种体内方法。为了实现耳蜗外淋巴微环境中抗坏血酸的体内电化学监测，将 MWNT 修饰的 CFME 用作工作电极，将微尺寸的 Ag/AgCl 用作参比电极，将 Pt 丝用作对电极。三个电极一起围绕在毛细管周围形成集成毛细管电极。将集成毛细管电极小心地植入豚鼠耳蜗外淋巴中，用于将水杨酸盐外部微灌注到耳蜗外淋巴中，并实时监测抗坏血酸水平的变化。基于集成毛细管电极的体内伏安法对豚鼠耳蜗外淋巴中的抗坏血酸具有高选择性和良好的线性关系。使用这种方法，确定豚鼠耳蜗外淋巴中的基础抗坏血酸水平为 45.0 ± 5.1 μM（n = 6）。将 10 mM 水杨酸盐（1 μL/min，5 min）微灌注到耳蜗中，将抗坏血酸水平降低至基础水平的 28 ± 10%（n = 6），具有统计学意义（P <0.05），这表明耳蜗中抗坏血酸水平的降低可能与水杨酸盐诱导的耳鸣有关。本研究为水杨酸盐诱导的耳鸣后耳蜗外淋巴中抗坏血酸的体内监测提供了一种新方法，因此可用于耳鸣相关化学本质的研究。
