Fig. 5

Effect of the L-type Ca²⁺ channel blocker nifedipine on cardiac Ca²⁺ levels and ventricular shortening of 3 and 5 dpf zebrafish larvae. Tg(myl7:Twitch-4) larvae at 3 (n = 11, N = 4) and 5 dpf (n = 12, N = 4) were treated with 100 µM nifedipine for 1 h. (A) Emission ratio images of a ventricular systole of representative larvae before (basal) and after the incubation with nifedipine. The traces show the atrial (red) and ventricular (black) Ca²⁺ levels (emission ratio) of these larvae. (B) Fold change over the basal HR of larvae treated with nifedipine. (C) Fold change of the average Ca²⁺ levels and amplitude of Ca²⁺ transients over their basal values in the atrium (At) and ventricle (Vt) (D) Diagrams of the ventricular vs. atrial Ca²⁺ levels (one cardiac cycle) of representative larvae before (basal) and after the incubation with nifedipine (note the different scale for 3 and 5 dpf). (E) Diagrams of the ventricular diameter vs. ventricular Ca²⁺ level (one cardiac cycle) of representative larvae before (basal) and after addition of nifedipine. The plot shows the fold change over the basal FS. All data are shown as the mean ± SD. A two-tailed unpaired Student's t-test was used (* p < 0.05, ** p < 0.01, *** p < 0.001).