[Ca²⁺]_i and membrane potential oscillations during stimulation with 12 mM glucose plus 10 mM tetraethylammonium (TEA).

<p><b>A</b> A high resolution image showing loading of cells with the calcium-sensitive dye OGB-1. <b>B</b> A color-coded representation of responsive cells from A with respect to time lags between the start₅₀ of [Ca²⁺]_i oscillation in the first cell and every other cell. <b>C</b> Time trace of a [Ca²⁺]_i oscillation during stimulation with 12 mM glucose plus 10 mM TEA in the cell indicated in B. <b>D</b> A high resolution image showing labeling of cells with the voltage-sensitive dye VF. Note that almost exclusively plasma membranes are labeled. <b>E</b> A color-coded representation of responsive cells from D with respect to time lags between the start₅₀ of membrane potential oscillation in the first cell and every other cell. <b>F</b> Time trace of a membrane potential oscillation during stimulation with 12 mM glucose plus 10 mM TEA in the cell indicated in D. The time scale is the same for C and F. Y axis represents the normalized fraction of the difference between maximum and plateau baseline fluorescence. <b>G</b> Durations of [Ca²⁺]_i oscillations (OGB-1: 1^st quartile=135 ms, median=166 ms, 3^rd quartile=248 ms, n=57 cells from three islets) and membrane potential oscillations (VF: 1^st quartile=81 ms, median=101 ms, 3^rd quartile= 162 ms, n=107 cells from five islets) at their half-maximal amplitude. Asterisks indicate a statistically significant difference (p<0.001, Mann-Whitney rank sum test). <b>H</b> Velocities of [Ca²⁺]_i waves (OGB-1: 1^st quartile=372 µm/s, median=623 µm/s, 3^rd quartile=1058 µm/s, n=8 values from three islets) and membrane potential waves (VF: 1^st quartile=457 µm/s, median=577 µm/s, 3^rd quartile=857 µm/s, n=12 values from five islets) were not statistically significantly different. Resolution was 256 x 64 pixels at 97 Hz for OGB-1 and 256x128 at 99Hz for VF.