Voltage‐clamp investigations of membrane currents underlying pace‐maker activity in rabbit sino‐atrial node.

Abstract

1. Small preparations of spontaneously beating rabbit sino‐atrial node have been investigated using the two micro‐electrode voltage‐clamp technique. 2. Hyperpolarizing clamp pulses given from holding potentials of about ‐45 mV reveal a time‐dependent change of a membrane current, if, which is shown to overlap the pace‐maker range (‐65 mV to ‐45 mV) for these preparations. 3. The changes in if are shown to be quite distinct from the de‐activation of the time‐dependent outward current, iK. 4. The time‐dependent changes of the if system increase during adrenaline application and therefore contribute to the chronotropic action of adrenaline on the heart. 5. Evidence for a link between slow inward current (iSi) and time‐dependent outward current (iK) in rabbit sino‐atrial node is presented and assessed.