Intact fibres of human intercostal and rat omohyoid muscles were studied at 23 degree C with a loose-patch voltage-clamp technique that employed two concentric micropipettes to electrically isolate small-diameter (10-15 microns) patches of sarcolemma. This method allows investigation of membrane excitability under highly physiological conditions. Step depolarizations to 0 mV elicited sodium inward currents that reached peak values of up to 20 mA/cm2 within 250 microseconds, and then declined. In human muscle, the reversal potential (ENa) was approximately 40 mV, and maximal conductances (GNa) ranged from 44 to 360 mS/cm2. In rat muscle, ENa was 42 mV and GNa ranged from 100 to 250 mS/cm2. Sodium channels in rat and human muscle were indistinguishable in most aspects of their kinetic behaviour and voltage dependence. Outward potassium currents were small by comparison (usually less than 2 mA/cm2) and saturated at positive potentials. The maximum potassium conductance (GK) ranged from 0 to 19 mS/cm2 (human) and from 4 to 12 mS/cm2 (rat muscle).
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机译：在23摄氏度下，采用宽松的电压钳技术研究了人肋间和大鼠舌舌肌的完整纤维，该技术使用两个同心微量移液管将小直径（10-15微米）的肌膜斑电隔离。该方法允许在高度生理条件下研究膜的兴奋性。逐步去极化至0 mV会引起钠内向电流，该电流在250微秒内达到最高20 mA / cm2的峰值，然后下降。在人体肌肉中，反向电位（ENa）约为40 mV，最大电导（GNa）范围为44至360 mS / cm2。在大鼠肌肉中，ENa为42 mV，GNa为100至250 mS / cm2。大鼠和人体肌肉中的钠通道在动力学行为和电压依赖性的大多数方面都无法区分。相比之下，向外的钾电流很小（通常小于2 mA / cm2），在正电势下饱和。最大钾电导（GK）范围为0至19 mS / cm2（人）和4至12 mS / cm2（大鼠肌肉）。
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