Properties and functions of calcium-activated K+ channels in small neurones of rat dorsal root ganglion studied in a thin slice preparation
Properties and functions of calcium-activated K+ channels in small neurones of rat dorsal root ganglion studied in a thin slice preparation
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DOI：
10.1111/j.1469-7793.1998.055by.x
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发表时间：
1998-11-15
影响因子：
5.5
通讯作者：
Vogel, W
中科院分区：
文献类型：
--
作者：
Scholz, A;Gruss, M;Vogel, W
1.采用膜片钳技术，在未经酶处理的背根神经节（DRG）薄片标本上，研究了小神经元（A δ型和C型）大电导钙激活钾通道（BKCa）的特性、动力学和功能.在对称的高Kf溶液（155 mM）中测量的BK 1通道的单位电导对于内向电流为200 pS，而对照溶液中的弦电导为72 pS。在-28 mV（pCa 4）~+100 mV（pCa 7）范围内，通道的半最大激活电位（V-1/2）线性移动43 mV/log [Ca ~（2+）]（i）单位（pCa）。每15-32 mV的电位去极化，开放概率增加e倍.平均开放概率主要在pCa > 6和电位> +20 mV时随时间快速变化，实验条件变化不明显.通过表观振幅降低测量，0.4mM TEA半最大程度地阻断BK 1通道。它们被100 nM的Charybdotoxin和50 nM的iberiotoxin通过降低开放概率而完全阻断。小DRG神经元的两种亚型可以通过BKCa通道的存在（I型）或不存在（II型）来区分。此外，只有不到10%的小神经元表现出快（类似于135 V s（-1））和短（类似于0.8 ms）的动作电位（AP）。BK_（1+）通道的主要功能是缩短AP时程，加快复极速度，促进快速后超极化。因此，BKCa通道可以减少AP期间进入神经元的钙的量。BKCa通道电流抑制随后的AP并延长不应期，这可能导致重复活动减少。我们认为，BKCa电流是一个可能的机制，在重复刺激DRG神经元的传导失败的报告。
1. Properties, kinetics and functions of large conductance calcium-activated K+ channels (BKCa) were investigated by the patch-clamp technique in small neurones (A delta- and C-type) of a dorsal root ganglion (DRG) thin slice preparation without enzymatic treatment.2. Unitary conductance of BK,, channels measured in symmetrical high Kf solutions (155 mM) was 200 pS for inward currents, and chord conductance in control solution was 72 pS. Potentials of half-maximum activation (V-1/2) of the channels were Linearly shifted by 43 mV per log,, [Ca2+](i) unit (pCa) in the range of -28 mV (pCa 4) to +100 mV (pCa 7). Open probabilities increased e-times per 15-32 mV depolarization of potential.3. In mean open probability, fast changes with time were mainly observed at pCa > 6 and at potentials > +20 mV, without obvious changes in the experimental conditions.4. BK,, channels were half-maximally blocked by 0.4 mM TEA, measured by apparent amplitude reductions. They were completely blocked by 100 nM charybdotoxin and 50 nM iberiotoxin by reduction of open probability.5. Two subtypes of small DRG neurones could be distinguished by the presence (type I) or absence (type II) of BKCa channels. In addition, less than 10% of small neurones showed fast (similar to 135 V s(-1)) and short (similar to 0.8 ms) action potentials (AP).6. The main functions of BK,, channels were found to be shortening of AP duration, increasing of the speed of repolarization and contribution to the fast after-hyperpolarization. As a consequence, BKCa channels may reduce the amount of calcium entering a neurone during an AP.7. BKCa channel currents suppressed a subsequent AP and prolonged the refractory period, which might lead to a reduced repetitive activity. We suggest that the BKCa current is a possible mechanism of the reported conduction failure during repetitive stimulation in DRG neurones.