Fig. 1

Action potentials in differentiating P19 cells. a Representative action potentials (APs) from a single isolated beating cardiomyocytes derived from P19 cells on differentiation day 14 with vehicle (control). Note that the APs exhibit distinct spontaneous diastolic depolarization with the maximum diastolic potential (MDP) of − 58.2 mV. b–d Representative action potentials (membrane potentials) in P19-derived cardiomyocytes on differentiation day 14 in the presence of 10 μM PD98059 (b), 10 μM SP600125 (c), and 10 μM SB203580 (d) recorded by the same protocol described in a