An improved vaseline gap voltage clamp for skeletal muscle fibers
An improved vaseline gap voltage clamp for skeletal muscle fibers
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一种改进的骨骼肌纤维凡士林间隙电压钳
DOI：
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发表时间：
1976
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通讯作者：
Donald T. Campbell
中科院分区：
文献类型：
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作者：
B. Hille;Donald T. Campbell
建立了一种用于蛙类骨骼肌纤维的凡士林间隙电位记录和电压钳法。该方法是在Frankenhaeuser-Dodge电压钳的基础上进行改进，以提高频率响应，补偿外部串联电阻，并补偿电流通过通路的复杂阻抗。单个肌肉纤维的碎片从半腱肌中拔出，并在用脑脊液等溶液去极化的同时安装。在流体池之间形成凡士林密封后，再次切割光纤端部，用林格溶液冲洗中心区域，并打开反馈放大器。电位和电流记录中的误差是通过微电极直接测量来评估的。用“圆盘”等效电路模拟了横向管状系统的无源特性，得到的参数与以前用微电极测量的参数相似。由于没有延迟整流，5℃时的动作电位很长。通过求解钠在表面和管状膜中渗透的圆盘模型，近似模拟了它们的形状。电压箝位电流主要由容量电流和钠电流组成。在5℃时，钠向内电流密度峰值为3.7 mA/cm2。在5℃时，钠电流平滑渐变，去极化增加，无缺口，表明对表面膜的控制良好。在较高的温度下，一个小的，晚额外的内向电流出现在小的去极化中，具有期望在横向管状系统中激发的性质。记录电流与模拟电流的对比表明，虽然横向管状系统具有再生钠电流，但它们太小，不会对低温下电压箝位下表面记录的总电流产生重大误差。这些小管绝对不是在电压钳控制下的。
A Vaseline gap potentiometric recording and voltage clamp method is developed for frog skeletal muscle fibers. The method is based on the Frankenhaeuser-Dodge voltage clamp for myelinated nerve with modifications to improve the frequency response, to compensate for external series resistance, and to compensate for the complex impedance of the current-passing pathway. Fragments of single muscle fibers are plucked from the semitendinosus muscle and mounted while depolarized by a solution like CsF. After Vaseline seals are formed between fluid pools, the fiber ends are cut once again, the central region is rinsed with Ringer solution, and the feedback amplifiers are turned on. Errors in the potential and current records are assessed by direct measurements with microelectrodes. The passive properties of the preparation are simulated by the "disk" equivalent circuit for the transverse tubular system and the derived parameters are similar to previous measurements with microelectrodes. Action potentials at 5 degrees C are long because of the absence of delayed rectification. Their shape is approximately simulated by solving the disk model with sodium permeability in the surface and tubular membranes. Voltage clamp currents consist primarily of capacity currents and sodium currents. The peak inward sodium current density at 5 degrees C is 3.7 mA/cm2. At 5 degrees C the sodium currents are smoothly graded with increasing depolarization and free of notches suggesting good control of the surface membrane. At higher temperatures a small, late extra inward current appears for small depolarizations that has the properties expected for excitation in the transverse tubular system. Comparison of recorded currents with simulations shows that while the transverse tubular system has regenerative sodium currents, they are too small to make important errors in the total current recorded at the surface under voltage clamp at low temperature. The tubules are definitely not under voltage clamp control.