Voltage-clamp investigations of membrane currents underlying pace-maker activity in rabbit sino-atrial node.
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.
D000818:Animals; D004837:Epinephrine / Q000494:pharmacology; D005711:Gallopamil / Q000494:pharmacology; D066298:In Vitro Techniques; D008564:Membrane Potentials / Q000187:drug effects*; D011188:Potassium / Q000502:physiology; D011817:Rabbits; D012849:Sinoatrial Node / Q000187:drug effects / Q000502:physiology*; D013268:Stimulation, Chemical; D013696:Temperature; D013779:Tetrodotoxin / Q000494:pharmacology
D005711:Gallopamil; D013779:Tetrodotoxin; D011188:Potassium; D004837:Epinephrine