Sarai, Matsuoka, Kuratomi, Ono, Noma, 2003

Model Status

This model has been curated and unit checked by Alan Garny in collaboration with the model authors and it is known to run in OpenCell and COR to reproduce the published results. The units have been checked and they are consistent.

Model Structure

ABSTRACT: This paper discusses the development of a cardiac sinoatrial (SA) node pacemaker model. The model successfully reconstructs the experimental action potentials at various concentrations of external Ca2+ and K+. Increasing the amplitude of L-type Ca2+ current (I(CaL)) prolongs the duration of the action potential and thereby slightly decreases the spontaneous rate. On the other hand, a negative voltage shift of I(CaL) gating by a few mV markedly increases the spontaneous rate. When the amplitude of sustained inward current (I(st)) is increased, the spontaneous rate is increased irrespective of the I(CaL) amplitude. Increasing [Ca2+](o) shortens the action potential and increases the spontaneous rate. When the spontaneous activity is stopped by decreasing I(CaL) amplitude, the resting potential is nearly constant (-35 mV) over 1-15 mM [K+](o) as observed in the experiment. This is because the conductance of the inward background non-selective cation current balances with the outward [K+](o)-dependent K+ conductance. The unique role of individual voltage- and time-dependent ion channels is clearly demonstrated and distinguished from that of the background current by calculating an instantaneous zero current potential ("lead potential") during the course of the spontaneous activity.

The original paper reference is cited below:

Role of Individual Ionic Current Systems in the SA Node Hypothesized by a Model Study, Sarai N, Matsuoka S, Kuratomi S, Ono K, and Noma A, 2003, The Japanese Journal of Physiology, 53, 125-134. PubMed ID: 12877768

A schematic diagram describing the ionic components of the Matsuoka et al. 2003 SA node cell mathematical model. Unique to the SA node cells are the acetylecholine-activated K+ current, IKACh, the hyperpolarisation-activated cation current, Iha, and the sustained inward current Ist.

A schematic diagram describing the reaction kinetics of the ion channel gates in the Matsuoka et al. 2003 mathematical models. A) The kinetics of the sodium channel voltage-dependent gate. B) The kinetics of the Na-Ca exchange pump. C) The kinetics of the Na-K pump. D) The kinetics of the inward rectifier K+ current. E) The kinetics of the Ca2+-dependent gate of the L-type Ca2+ channel. F) The kinetics of the ultra-slow gates of several ion channels. G) The kinetics of the SR Ca2+ pump. H) The kinetics of the hyperpolarisation-activated cation current. I) The kinetics of the RyR channel in the SR.