Ionic currents during action potentials in mammalian skeletal muscle fibers analyzed with loose patch clamp

Experimental analysis of transmembrane currents during action potentials in mammalian skeletal muscle fibers, using loose patch-clamp technique identifies three current components, namely a capacitive, an inward sodium and an outward potassium current. Potassium channel activity is unavailable for loose patch extracellular voltage-clamp stimulation and only sodium current occurs with extracellularly applied depolarization steps. The potassium current is, however, crucial for depolarization of the intracellular action potential of muscle fibers.