Figure 6.

Intracellular Ca²⁺ transients in response to increase in frequency and membrane potential measurements. Stimulation from 0.5 to 4 Hz. A) representative traces of intracellular Ca²⁺ in myocytes from adult Wt (n = 35) and TREK-1 KO (n = 27) myocytes (isolated from 4 mice each group). The numbers on the traces indicate the frequency of stimulation and transients evoked at 0.5, 1, and 2 Hz. B) Intracellular Ca²⁺ at resting level while stimulated at the correspondent frequency, values measured at the resting level indicated by the arrow-heads in panel A. C) Optical measurements of action potentials duration (AP) by using a voltage-sensitive dye (FluoVolt). Comparison of action potential measured using FluoVolt loaded cardiomyocyte isolated from TREK-1 KO and WT hearts. Cells were paced electrically at 1-Hz and AP waveform was recorded as a FluoVolt fluorescence signal. The figure shows a representative trace from each group containing five peaks superimposed to emphasize action potential prolongation in TREK-1 KO cardiomyocytes (arrow-heads, red trace). B) Peaks were evaluated for time to baseline (APD90%), five peaks from each cell were averaged, each point represents APD averaged from each heart 15 cells/5 hearts. Values are presented as mean ± S.E.*P < 0.05 compared to the control group.