Simultaneous imaging of V_m and [Ca²⁺]_i in a Langendorff-mode saline-perfused rat heart.

<p>(<b>A</b>) V_m (red) and [Ca²⁺]_i (green) fluorescence signals (camera signals on a 16-bit scale) taken from the 4×4-pixel white-square region on the left ventricle. (<b>B</b>) Normalized fluorescence intensity maps (colorbar shown) at progressive time points during sinus rhythm. The delay of the CaT relative to the AP peak (∼17 ms from transients in part <b>A</b>) is clearly visible. Scale bar = 5 mm. For these images, blebbistatin was used to eliminate the contribution of motion to the signals.