Zinc release from a bipolar stainless steel electrode. '+' indicates the beginning of current passage with the bottom electrode as the anode, while '-' denotes that the polarity was reversed. A 100 Hz square wave with pulse duration of 30 μs was applied for 2.5 s at a current amplitude of 500 μA. The experiment was performed in Hepes saline with 2μM NPG and 50 μM Ca-EDTA. Pseudocolor images are the differences between the fluorescence at the peak of the response and that immediately prior to delivering the stimulus; Left '+' stimulus, right '-' stimulus. Color bar 0–50. Scale bar 100 μm.