Secreted vesicles were immobile immediately before fusion.

<p>(<b>A</b>) Histogram of the averaged lateral CD distribution of secreted vesicles from cells at a pre-stimulus [Ca²⁺]_i of 590 nM (black). Data points are represented by circles, whereas solid lines represent the best fit by a single log-normal and two Gaussian components. Cells were stimulated by a train of ten depolarizations (5 Hz) 10 s before the end of the imaging period. The CD values were calculated from the last 15 s prior to fusion. The two fits obtained from cells kept at 100 nM (blue) and 700 nM (orange) [Ca²⁺]_i were plotted for comparison. (<b>B</b>) Average secretion of 19 cells stimulated 1 to 2 times. The increase in membrane capacitance is shown in red and the averaged cumulative number of exocytotic events visualized by TIRF-microscopy in black. The type of mobility of these LDCVs prior to secretion is indicated by grey filled circles (immobile) and grey empty boxes (caged). All curves were aligned to the onset of the stimulus. N_100nM/n: 23/719; N_700nM/n: 14/309; N_secreted/n: 19/53.