胞外高钾对大鼠背根神经元超极化电流的影响

应用全细胞膜片钳技术研究了胞外高钾对大鼠背根神经元（DRG）超极化电流（Ih）的影响．结果表明，Ih随着胞外钾离子浓度的增大而增大，同时随着外加刺激电压的增高而增强．当胞外钾离子浓度[Kext]为4，8和16mmol／L时，半数激活电压V1/2分别为-98±1．9，-106±1．3（p〈0．05）和-110±1．0mV（p〈0．05），其对应的最大电流的峰值分别为1085±340，1576±409和2124±614pA，与4mmol／L比较，后者分别增长了45％和92％．胞外高钾使，Ih激活曲线显著左移，说明高Kext改变了超极化电流的激活过程．提高细胞外钾离子浓度，可以使早期钾通道（又称快通道）的激活时间常数增大，使晚期钾通道（又称慢通道）激活时间常数减小．当胞外钾离子浓度由4mmol／L升高到8和16mmol／L时，翻转电位右移，但不具有显著性差异．结果提示，细胞外高浓度钾可增强大鼠背根神经元超极化电流，Ih，改变Ih的激活过程，从而提高了神经元的兴奋性，产生不正常的动作电位，对神经细胞产生损伤．

The effects of rises in external K~+ on the hyperpolarization-activated cation current Ih in rat dorsal root ganglion neurons

The effects of rises in external K^＋ （Kext） were examined on the hyperpolarization-activated cation current （Ih） in rat dorsal root ganglion neurons using the whole-cell patch clamp technique. The results showed that external K^＋ （Kext） increased lh in a certain concentration and voltage-dependent manner. At the basal Kext level （4 mmol/L）, Ih had a maximal amplitude of 1085±340 pA which was enhanced by -45% and -92% at 8 and 16 mmol/L Kext respectively. The midpoint activation voltage was significantly shifted from -98 mV in the hyperpolarizing direction by 8 and 12 mV at 8 and 16 mmol/L Kext respectively with alteration of the activation course of lb. The short time constants of activation became longer with increasing amplitude of the command potential upon rises in Kext. The long time constants became shorter. The reversal potentials were shifted in the positive direction without significant alterations upon rises in Kext. According to the functional role of Ih, Kext increased Ih resulting in an enhanced neuronal excitability, which might produce activation potential abnormality and perhaps neuropathic pain involved.