Ionic current and pacemaker activity of the S-A node cells

Abstract

1) Five membrane current (if, is, ik, ih, il) were observed in rabbit S-A node cells by the voltage clamp method. 2) The outward current (ik) was carried by k ion, while the inward current (is) was mainly carried by Na ion with some contribution of Ca ion. The inward current activated by hyperpolarization (ih) ws a mixed current system, but participation of Na and Cl ions was found to be existed. 3) Each current was analysed according to the Hodgkin-Huxley type equation. 4) Finally the action potential and pacemaker activity of S-A node were reconstructed. 5) In phase 4 diastolic depolarization, is played the major role, but the assistance of ik ws also important.