Effect of cMyBP-C ablation on mECT contractile intervals. (A and B) Averaged amplitude-normalized twitch traces of WT and cMyBP-C^−/− mECT paced at 6 (A) and 9 Hz (B). Solid blue lines show vehicle-treated WT mECT, solid red lines show vehicle-treated cMyBP-C^−/− mECT, dashed blue lines show dobutamine-treated WT mECT, and dashed red lines show dobutamine-treated cMyBP-C^−/− mECT. AU, arbitrary units. (C and D) Contraction times from electrical stimulus to 50% of F_Max (CT₅₀; C) and from 50% F_Max to F_Max (CT_50–100; D) are shown. (E and F) Relaxation times from F_Max to 50% twitch force decay (RT₅₀; E) and 50 to 90% twitch force decay (RT_50–90; F) are shown. (C–F) Blue closed bars show vehicle-treated WT mECT, red closed bars show vehicle-treated cMyBP-C^−/− mECT, blue striped bars show dobutamine-treated WT mECT, and red striped bars show dobutamine-treated cMyBP-C^−/− mECT. *, P < 0.05 (one-way ANOVA with Tukey’s post hoc test; WT, n = 6; cMyBP-C^−/−, n = 7). (A–F) Error bars indicate SEM.