去甲肾上腺素抑制大鼠耳蜗螺旋神经元γ氨基丁酸门控氯通道电流

目的 研究去甲肾上腺素(noradrenaline,NA)对培养大鼠耳蜗螺旋神经元γ氨基丁酸(gamma-aminobutyric acid,GABA)诱发电流的作用.方法分离培养大鼠耳蜗螺旋神经元,采用制霉菌素穿孔膜片钳全细胞记录技术,记录NA对GABA诱发电流的作用.结果 大鼠螺旋神经元GABA诱发反应的反转电位为(-0.78±0.05)mV(n=8),与Cl-平衡电位一致.GABA在钳制电位为-50 mV时,可引起内向电流,EC50为(5.2±0.5)μmol/L,Hill系数为1.03(n=26),该电流可被GABA-A受体拮抗剂荷包牡丹碱抑制,NA对该电流具有抑制作用.结论 NA可以抑制螺旋神经元GABA-A受体介导的门控氯通道电流,该作用可能与交感神经系统对听觉的调控有关.

Inhibition of gamma-aminobutyric acid receptor-gated chloride currents by noradrenaline in rat spiral ganglion neuron

OBJECTIVE: To investigate the pharmacological modulatory properties of noradrenaline in the rat spiral ganglion neuron. METHODS: Nystain perforated patch recording technique under voltage-clamp conditions was used to record the modulatory effect of noradrenaline on the current evoked by gamma-amino butyric acid (GABA) in the spiral ganglion neuron. RESULTS: The reversal potential of the GABA response was about (- 0.78 +/- 0.05) mV (n = 8), which was almost identical to the theoretical Cl- equilibrium potential. At the holding potential of -50 mV, GABA evoked inward current (I(GABA)) over the concentration range of 0.3 to 1 micromol/L. The EC50 and Hill coefficient for GABA were (5.2 +/- 0.5) micromol/L and 1.03 (n = 26). The I(GABA) was suppressed by bicuculline, the selective GABA-A receptor antagonist, and the chloride currents evoked by GABA was inhibited by noradrenaline. CONCLUSIONS: The result indicates that noradrenaline depressed GABA-A receptor-gated chloride currents, which may contribute to the modulatory effect of sympathetic system on auditory transmission.