Fig. 10.
[Ca2+]i is depressed by nonxanthine store-releasing compounds and after spontaneous calcium spikes. A, 4-Chloro-m-cresol (500 μm) evoked a transient peak and a subsequent depression in [Ca2+]i.B, Ratios (340/380 nm) from two simultaneously recorded rods in 20 mmKCl are plotted. In this particular recording session, we were not able to perform absolute calibrations of [Ca2+]i on these particular cells and so have used the 340/380 ratio as the indicator of calcium concentration. Caffeine (10 mm) was applied at 14.9 and 35.4 min. At t = 23.7 min, rod 2 (bottom solid line) exhibited a spontaneous regenerative increase in [Ca2+]i(thick open arrow) followed by an undershoot (thin filled arrow). No such phenomenon was exhibited by rod 1 (top dotted line).