Abstract
Duration of the plateau phase (phase 2) of action potentials in pacemaker cells in mouse sinoatrial node characterized by low upstroke rate during the rapid depolarization (dV/dt max <7 V/sec, phase 0) and in atrial-like cells with dV/dt max <100 V/sec were prolonged by 50% with 4-aminopyridine in concentrations of 0.7 and 0.1 mM, respectively. This blocker did not lengthen the terminal repolarization (phase 3). The above changes were accompanied by a 20-80% decrease in dV/dt max in comparison to the control. It is hypothesized that the short-term (transient) outward current Ito takes a part in the plateau formation and modulates the duration of the rapid depolarization phase of action potentials in mouse sinoatrial node cells.
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