Yang Kun, Huang Zhi-Wu, Huang Juan, Zhang Xiao-Jun, Xiao Bo-Kui
Department of Otolaryngology-Head & Neck Surgery, Renmin Hospital of Wuhan University, Wuhan 430060, People's Republic of China.
Neurosci Lett. 2008 Aug 22;441(2):205-9. doi: 10.1016/j.neulet.2008.06.038. Epub 2008 Jun 18.
Auditory transduction in the cochlear is subject to modulate higher auditory centers in the brain via the efferent systems, which provide protection against damage caused by excessive excitation during auditory over stimulation. GABA is a proven inhibitory neurotransmitter in the efferent systems in mammalian cochlear. KCC2 is a neuron-specific potassium chloride cotransporter whose role in mature central neurons is to maintain the low intracellular Cl(-) concentrations required for the hyperpolarizing responses to the inhibitory amino acids GABA and glycine. However, there is a lack of information concerning KCC2 expression in the mammalian cochlear. In this study, reverse-transcription polymerase chain reaction (RT-PCR) and immunohistochemistry were used to detect the expression and localization of KCC2 in the mammalian cochlear. The results showed that these neuron-specific KCC2 transporters were present in most spiral ganglion neurons (SGNs) corresponding to the distribution of GABA(A)Rs. In addition, less intense reactions were observed on the organ of Corti, stria vascularis, and fibrocytes of the spiral ligament. These data suggest that KCC2 may play an important role in the modulation of a GABA neurotransmitter's function in a mammalian cochlear. Moreover, the presence of KCC2 on the organ of Corti and its surrounding tissues may contribute to maintaining normal K+ cycling. It is also presumed to be related to Cl(-) transportation in hair cells.
耳蜗中的听觉转导可通过传出系统调节大脑中的高级听觉中枢，该传出系统可防止在听觉过度刺激期间因过度兴奋而造成损伤。γ-氨基丁酸（GABA）是哺乳动物耳蜗传出系统中已被证实的抑制性神经递质。钾氯共转运蛋白2（KCC2）是一种神经元特异性的钾氯共转运体，其在成熟中枢神经元中的作用是维持对抑制性氨基酸GABA和甘氨酸产生超极化反应所需的低细胞内氯离子（Cl⁻）浓度。然而，关于KCC2在哺乳动物耳蜗中的表达情况却缺乏相关信息。在本研究中，采用逆转录聚合酶链反应（RT-PCR）和免疫组织化学方法检测KCC2在哺乳动物耳蜗中的表达及定位。结果显示，这些神经元特异性的KCC2转运体存在于大多数与GABA(A)受体分布相对应的螺旋神经节神经元（SGN）中。此外，在柯蒂氏器、血管纹和螺旋韧带的纤维细胞上观察到较弱的反应。这些数据表明，KCC2可能在调节哺乳动物耳蜗中GABA神经递质的功能方面发挥重要作用。此外，KCC2在柯蒂氏器及其周围组织中的存在可能有助于维持正常的钾离子循环。据推测，这也与毛细胞中的Cl⁻转运有关。
