Voltage clamp method on single cardiac cells from adult rat heart

Voltage clamp experiments on isolated cardiac cells from adult rat hearts were carried out using an intracellular dialysis method. The fast inward current was recorded. Tetrodotoxin (TTX) at a concentration of 2.5 x 10(-7) g/ml blocked this current to 30% of its initial value. Inward maximal fast current density was calculated to be 0.14--0.7 mA/cm2.