Fig. 2.

Effects of ion channel inhibitors on field potential (FP) of hiPSC cardiac clusters.

A) Raw FP signal from a single MEA electrode, showing the effect following 6 mins superfusion of 500 nM isoprenaline (black arrow). B) Schematic of MEA protocol, with phase contrast image inset of cardiac clusters loaded onto an MEA. Bar = 500 μm. C) Representative ensemble FP signals at individual electrodes, showing effect of increasing doses of ajmaline, mexiletine or dofetilide on iPS-HS1M clusters. Arrow heads indicate examples for time points of activation and recovery peaks, to calculate cFPD. Grey dashed line shows 0 μV. D–E) Mean iPS-HS1M cluster activation-recovery interval over increasing drug doses (D), or activation complex downslope gradient dV/dt(minimum) at highest drug dose (E), showing effect of ajmaline (n ≥ 9), mexiletine (n ≥ 9) and dofetilide (n ≥ 4, some clusters ceased beating or were too inconsistent to generate ensemble averages at higher doses) normalised to baseline, error bars show ± s.e.m. One way ANOVA followed by Tukey HSD (D) or paired t-test (E), ** = p ≤ 0.01 or * = p ≤ 0.05 respectively vs baseline before normalisation.