[Effects of hyperpolarizing currents on the action potentials of nodal and perinodal sino-atrial cells of the rabbit heart].

A technique of focal polarization allowed us to confirm that the action potentials of the true rabbit heart pacemaker cells possess a rapid sodium channel normally inactivated because of the low value of the take-off potential of this tissue. The latent pacemaker cells are regular sinocaval cells depolarized as a consequence of the proximity of true pacemaker cells.