Figure 3. Effect of a 20 min pulse of 35 mM KCl on [Ca²⁺]_in of a superfused photoreceptor cell

Cells were continuously superfused with BSS (0-4 min; 24-31 min) or modified BSS containing 35 mM K⁺ (4-24 min), as described in Methods. Fluorescence emission ratios were obtained at 10 s intervals throughout the experiment. Depolarization induced a large increase of [Ca²⁺]_in and this increase remained for as long as the elevated [K⁺]_out was applied. The [Ca²⁺]_in of the cell rapidly returned to basal levels when the high K⁺ BSS was washed out of the superfusion well. This type of response is representative of that recorded from 3 cells.