Hyperpolarization-activated current (I-h) in primary auditory neurons
Hyperpolarization-activated current (I-h) in primary auditory neurons
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DOI：
10.1016/s0378-5955(97)00078-6
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发表时间：
1997-08-01
期刊：
影响因子：
2.8
通讯作者：
Chen, C
中科院分区：
文献类型：
--
作者：
Chen, C
据信，超极化激活电流（称为 I-h）可在窦房结细胞以及一些中枢和外周神经元中提供起搏器去极化。在本研究中，我们使用全细胞膜片钳技术检查了初级听觉神经元中是否存在这种内向阳离子电流。在超极化步骤中观察到大的向内非失活电流，其静息电位为负值。在超极化电流注入期间发生去极化凹陷，并且在电流注入终止时出现过冲或回弹激发。低浓度的 Cs+（而非 Ba2+）可以可逆地阻止内向电流和去极化凹陷。电流的激活表现出电压依赖性，半激活发生在-101 +/- 1 mV。激活的时间过程通过双指数函数拟合并且与电压相关（时间常数：-100 mV 时 tau(1) 和 tau(2) = 480 和 3125 ms，-160 mV 时 66 和 404 ms）。从尾电流测量，电流的反转电位为-36 mV。电流电导在无Na+溶液中降低，在高K+溶液中升高。细胞内 cAMP 或 cGMP 水平的增加增强了电流。结果表明，哺乳动物初级听觉神经元中存在超极化激活的内向阳离子电流。该电流可以在初级听觉神经每次放电之后的膜超极化期间提供去极化电流。
A hyperpolarization-activated current (termed I-h) is believed to provide a pacemaker depolarization in sinoatrial node cells and in some central and peripheral neurons. In the present study, we examined if such an inward cation current exists in primary auditory neurons using the whole-cell patch-clamp technique. A large inward, non-inactivating current was seen during hyperpolarizing steps negative to the resting potential. A depolarizing sag occurred during hyperpolarizing current injection, and upon termination of the current injection there was an overshoot, or a rebound firing. A low concentration of Cs+, but not Ba2+, reversibly blocked the inward current and depolarizing sag. The activation of the current showed voltage dependence with half-activation occurring at -101 +/- 1 mV. The time course of a activation was fitted by double exponential function and was voltage-dependent (time constants: tau(1) and tau(2) = 480 and 3125 ms at -100 mV, and 66 and 404 ms at -160 mV). The reversal potential of the current was -36 mV measured from tail currents. The conductance of the current was decreased in Na+-free solution, and increased in high K+ solution. Increases in the levels of intracellular cAMP or cGMP enhanced the current. The results suggest that there exists a hyperpolarization-activated inward cation current in mammalian primary auditory neurons. This current may provide a depolarizing current during the membrane hyperpolarization following each firing of the primary auditory nerve.