Fig. 6

Depolarization does not activate Ca_V1.3 channels in all cells. a–c Example neuromast with immunostain labeling presynaptic ribbons (Ribeye b, magenta) in a, and presynaptic Ca_V1.3a channels (cyan) in b. Images in a and b are merged in c. d Quantification of the percent of Ribeye b positive ribbons per neuromast that colocalize with Ca_V1.3a (93.00% ± 1.93, n = 10 neuromasts). e–h Representative neuromast demonstrating spatial patterns of hair-cell presynaptic GCaMP6s Ca²⁺ signals during mechanical and high K⁺ stimulation. Signals are colorized according to the ∆F/F heat map and superimposed onto baseline GCaMP6s image (e). f A subset of cells shows presynaptic Ca²⁺ signals in response to a 2-s 5 Hz mechanical stimulus. g All mechanical responses are eliminated after BAPTA treatment. h After BAPTA treatment, to depolarize hair cells, high K⁺ was applied (via the fluid jet). High K⁺ application activates the same cells as the original mechanical stimulus (f). i, l Example neuromasts demonstrating spatial patterns of hair-cell Bongwoori voltage signals during high K⁺ stimulation. Spatial patterns of Bongwoori voltage signals during high K⁺ stimulation are colorized according to the ∆F/F heat map and superimposed onto baseline Bongwoori image (i, l, left panels). k, n Using 5 µm ROIs shown in j, m, all cells show depolarization in response to high K⁺ application. Inset in k demonstrates that changes in Bongwoori signals in the background skin pigment (ROIs a, b) do no correlate with the stimulus. Scale bars = 5 μm