Functional roles of the L-type calcium channel on cardiac pacemaking — Insights from bifurcation analysis

In this study, we used the bifurcation analysis technique to study the functional roles of the maximal channel conductace of the L-type calcium channel coded by isoforms of Cav1.2 and Cav1.3 in a novel mathematical model of murine sinoatrial node (SAN) cells. A continuous variation in the maximal channel conductance of I_CaL (g_{CaL, 1.2} and g_{CaL, 1.3}) was carried out to reveal the emergence and annihilation of pacemaking action potentials (APs), changes in AP´s cycle length, maximal diastolic potential and overshoot. Parameter value range of the channel conductances essential for generating or annihilating pacemaking APs were identified. Our data demonstrates that the L-type calcium channel current contributes to cardiac pacemaking APs, especially during their diastolic and up-stroke depolarization phases.