Abstract

For many years, local circuit current through gap junctions has been seemed to be the main fundamental route for impulse transmission. In the last few years, some different evidences suggest another view on action potential propagation via myocardial cells. Some researches offered that myocardial cells may not require low-resistance connections for successful propagation of action potential. It seems that some other mechanisms are involved in the action potential propagation. Electrical field has been suggested as the main effective mechanism in action potential propagation. It is demonstrated that in the lack of gap junctions, electrical field is sufficient for action potential propagation. We simulated the mechanism of electrical field and local circuit current separately, studied the effect of these mechanisms on action potential propagation and compared them with each other. Our results demonstrate that although the mechanism of electrical field alters the resting potential of the post-junctional cell, but it is not sufficient to excite the post-junctional cell. These results offer a new view on action potential propagation in which both of the abovementioned mechanisms are necessary for normal cardiac functioning, but in different times of a cardiac cycle. It seems that gap junction has a dynamic behavior in each cardiac cycle, managing different routes of propagation in the diverse moments of normal cycle. Closure of gap junctions allows the negative cleft potential to develop and enhance the cell excitability by reducing cell potential. Then opening the gap junction produces AP. Based on this view, we think that most of the paradox about the role of gap junctions in cardiac impulse propagation will be solved.