FIGURE 4.

Changes in first-puff latencies with Ca²⁺ influx and 3-deaza-cADPR. Latencies were measured as the time from end of the photolysis flash to the observation of the first puff at any given site. A, mean values of latencies in control and 3-deaza-cADPR-injected oocytes before (open bars) and after (filled bars) Ca²⁺ influx. Paired measurements were made in each oocyte before and after Ca²⁺ influx and show significant differences for both experimental groups; but wide experimental variation between oocytes makes statistical comparison difficult between control and 3-deaza-cADPR groups. B, increases in mean puff latencies with Ca²⁺ influx and 3-deaza-cADPR largely arise from the appearance of long-latency puffs. Histograms show the proportion of initial puffs under each experimental condition that arose within <2s, 2–5s, and >5s following the photolysis flash. C and D, distributions of first-puff latencies before (open bars) and after Ca²⁺ influx (filled bars) in control (C) and 3-deaza-cADPR-injected oocytes (D). Data are plotted on 3 timescales to more clearly illustrate the relative invariance of the population of short latency (<2s) puffs, and the appearance of puffs with latencies of tens of seconds. Measurements were obtained from 11 control oocytes and 10 oocytes injected with 3-deaza-cADPR. Curves are single exponential fits to data at latencies <2s.