Wang H H, Yeh J Z, Narahashi T
J Membr Biol. 1982;66(3):227-33. doi: 10.1007/BF01868497.
The effects of spin-labeled local anesthetics on sodium currents of internally perfused squid axons were studied using the voltage-clamp technique. Internal application (10 mum) of the most potent spin-labeled local anesthetic used in this study produced a small initial block of sodium currents. However, after sixty repetitive pulses (to + 80 mV) given at 1 Hz, the sodium currents were drastically reduced. In addition to this frequency-dependent phenomenon, the anesthetic effect on the sodium currents was also sensitive to the voltage of the pulses. Both the frequency- and voltage-dependent properties remained intact after removal of sodium inactivation with pronase. The recovery of sodium currents from this frequency-dependent anesthetic effect followed a single exponential curve with a surprisingly long time constant of about 10 min. Such a long recovery time, which is longer than any known sodium inactivation process, led us to suggest that the recovery process represents the dissociation of drug molecules from their binding sites. We have also found that increasing hydrophobic character of the homologues series of spin-labeled local anesthetics enhances the frequency- and voltage-dependent block of sodium currents. This effect strongly suggests that hydrophobic interaction is an integral component of the binding site. These probes with their selective effects on the sodium currents, are expected to be highly useful in studying the molecular structure of the sodium channels.
运用电压钳技术研究了自旋标记局部麻醉药对经内部灌注的枪乌贼轴突钠电流的影响。在本研究中，使用体内应用（10μm）最有效的自旋标记局部麻醉药会使钠电流产生一个小的初始阻滞。然而，在以1Hz给予60个重复脉冲（至+80mV）后，钠电流急剧降低。除了这种频率依赖性现象外，麻醉药对钠电流的作用还对脉冲电压敏感。在用链霉蛋白酶消除钠失活后，频率依赖性和电压依赖性特性均保持不变。钠电流从这种频率依赖性麻醉效应中的恢复遵循单指数曲线，其时间常数惊人地长，约为10分钟。如此长的恢复时间，比任何已知的钠失活过程都要长，这使我们认为恢复过程代表药物分子从其结合位点的解离。我们还发现，自旋标记局部麻醉药同系物系列疏水性的增加会增强钠电流的频率依赖性和电压依赖性阻滞。这种效应强烈表明疏水相互作用是结合位点的一个组成部分。这些对钠电流具有选择性作用的探针，有望在研究钠通道的分子结构方面非常有用。
