CONTRIBUTION OF TIME-INDEPENDENT CURRENTS TO THE PACEMAKER POTENTIAL OF SINOATRIAL NODE CELLS USING A SIMULATION-MODEL

We investigated the roles of the time-independent currents in sinoatri al node cells revealed by mathematical models. The time-independent ba ckground current (Ib) was expressed by Goldman-Hodgkin-Katz equations, and the Na-K pump current (Ip) and the Na-Ca exchange current (I-NaCa ) were expressed using an original model based on the Chapman-Johnson- Kootsey chemical model, and by the model described by Hilgemann and No ble, respectively. According to these models, it was found that the ou tward current through Ip of around 10 pA contributed to the pacemaker potential. Ib and I-NaCa contributed as inward currents during pacemak er potential, and their amplitudes were around -9 and -4 pA, respectiv ely.