Figure 2. Amperometry recordings of catecholamine release from chromaffin cells with tetraspanner manipulations. A, Representative recordings from WT cells, syp KO cells, syp KO cells transfected with WT syp (syp KO+syp), syp KO cells transfected with syp-dC (syp KO+dC), WT cells overexpressing full-length syp (WT+syp), and syp/syg DKO cells. The lines below each trace indicate the time of depolarization by high KCl application. B, The frequency of spikes (amplitudes >4 pA) from the first stimulation, presented as cell-mean. C, Pooled cumulative spike counts from the first stimulation of each cell, plotted to show fusion events versus time (normalized to cell number). As in B, the line below indicates the time of depolarization. D, The slope of the rise from 10% to 70% of the plateau from the cumulative plots in C. Cell numbers: WT, N = 77; syp KO, N = 75; syp KO+Syp, N = 53; syp KO+dC, N = 41; WT+syp, N = 29; DKO, N = 72 cells; *p < 0.05, **p < 0.01, ***p < 0.001, by one-way ANOVA with the Tukey's post hoc test.