Figure 3. Reproducibility of spiking.

A) Patch clamp voltage recordings of spontaneously spiking HEK cells at different levels of confluence. Although the beat rate varied with cell density, the rising edge was consistently fast (2-3 ms) and the variation in the voltage swing was typically ~10% between dishes. B) Representative fluorescence traces from eight different dishes treated with the voltage sensitive dye VF2.1.Cl. Fluorescence was recorded at a 1 kHz frame rate. C) Histogram of fluorescent spike amplitudes. D) Histogram of spike rise time (40% to 70% depolarization) as recorded optically. Histograms show the aggregate results from 13 dishes of cells and 15 locations within each dish.