Büsselberg D, Michael D, Evans M L, Carpenter D O, Haas H L
Heinrich-Heine Universität Düsseldorf, Physiologisches Institut II, FRG.
Brain Res. 1992 Oct 9;593(1):77-81. doi: 10.1016/0006-8993(92)91266-h.
Dorsal root ganglion cells (DRGs) exhibit 3 types of voltage-dependent calcium channels. We have cultured DRGs from 2- to 4-day-old rat pups and obtained whole-cell patch-clamp recordings of calcium-channel currents after 1-5 days in culture. The calcium-channel currents (carried by barium) were recorded with tetrodotoxin (TTX) in the external solution. A cesium-based solution containing Na-ATP, HEPES and EGTA was used in the recording pipette. Cells were held at -80 mV and calcium channel currents were evoked by stepping to depolarized voltages. The divalent cation zinc (Zn2+) blocked sustained and transient voltage sensitive calcium channel currents. Onset of the blockade was fast and a steady-state was reached within 5-15 min, depending upon the concentration used. The IC50 for inhibition of the peak current evoked by a step depolarization from -80 mV to 0 mV (N plus L channels) for 80 ms was 69 microM Zn2+ and the Hill slope about 1. The calcium current evoked by a voltage step from -80 mV to voltages between -40 mV and -15 mV (T-type current) was more sensitive (> 80% block with 20 microM Zn2+). During wash the effect was only partly reversible in 50% of the neurons. Thus, Zn2+ is a potent blocker of voltage dependent calcium currents in mammalian neurons, especially of T-type currents.
背根神经节细胞（DRGs）表现出3种电压依赖性钙通道。我们从2至4日龄的大鼠幼崽中培养背根神经节，并在培养1至5天后获得钙通道电流的全细胞膜片钳记录。在外部溶液中用河豚毒素（TTX）记录钙通道电流（由钡携带）。记录电极中使用含有Na-ATP、HEPES和EGTA的铯基溶液。细胞保持在-80 mV，通过将电压阶跃到去极化电压来诱发钙通道电流。二价阳离子锌（Zn2+）阻断持续和瞬时电压敏感钙通道电流。阻断的起始很快，根据所用浓度，在5至15分钟内达到稳态。从-80 mV到0 mV（N加L通道）进行80 ms的阶跃去极化诱发的峰值电流抑制的IC50为69 microM Zn2+，希尔斜率约为1。从-80 mV到-40 mV至-15 mV之间的电压进行电压阶跃诱发的钙电流（T型电流）更敏感（20 microM Zn2+时>80%阻断）。在冲洗过程中，50%的神经元中这种效应仅部分可逆。因此，Zn2+是哺乳动物神经元中电压依赖性钙电流的有效阻断剂，尤其是T型电流。
