 To achieve bursts, a persistent sodium current provides enough depolarization to facilitate the firing of action potentials during a burst.Unlike the fast and transient sodium current, the persistent sodium current (INaP) is activated at very low membrane potentials and has a much slower inactivation, which allows neurons to intrinsically fire action potentials at sub-threshold membrane potentials.Studies have shown that the inactivation of this persistent sodium current helps end bursts in pacemaker neurons.