Figure 6. Effect of catecholamines on spontaneously beating clusters of EBs after acute application of reserpine.

Representative FP frequencies of day 11 to 12 beating cardiac clusters under acute presence of reserpine (10 µM) and after recovery with adrenergic receptor agonists (A) ISO (1 µM), (B) epinephrine (EPI, 100 nM) and (C) norepinephrine (NE, 100 nM). EBs were incubated with reserpine until maximum negative chronotropic effects were observed (between 8–30 min) and then co-applied with the adrenergic agonist as stated. Depicted are frequency-time plots of representative 60 sec intervals during the experiment. 10 sec FP traces are showcased on top of each. Note: After rescue with epinephrine no washout could be recorded. Full summary of all EBs measured is shown in Table 2.