Figure 2. Spatiotemporal Dynamics of Calcium Changes in a Rod Photoreceptor.

Sequential images of [Ca²⁺]_i changes were recorded from a Fura 2–loaded rod. Between (a) and (b), the rod was surperfused with high KCl. The images in (b) and (c) were captured 3 and 21 s after KCl application, respectively. The image in (d) was captured 15 s after KCl was replaced by LiCl. The image in (e) was captured 7 s after the return to control saline. These images show that KCl-evoked increases in [Ca²⁺]_i occurred most rapidly in the synaptic terminal region and then in the basal region of the inner segment. In LiCl, the IS and synaptic terminal returned to baseline while [Ca²⁺]_i in the OS rose, most notably at the tip. The pseudocolor scale representing the 256 gray levels of the 340/380 ratios is shown on the bottom; red indicates the largest changes. Scale bar, 10 μm.