Figure 7.

Overexpression of the Syt1-RQ mutant does not alter secretion in wild type chromaffin cells. A, Mean membrane capacitance, Ca²⁺, and amperometry measurements of wild-type (blue), with Syt1-wt overexpression (black) and Syt1-RQ mutant (red). B, Quantification of preflash [Ca²⁺]. C, The burst size was slightly higher in Syt1-wt overexpression than in Syt1-RQ overexpression and syt1 null, but this was not significant (Kruskal–Wallis, p = 0.149). D, The total release (ΔC_m at 5.5 s) was unchanged between conditions. E, No difference was detected for sustained release (ΔC_m at 5.5–1 s). F, G, I, J, Fitting individual capacitance traces with a sum of exponentials allowed separating the amplitude and time constant of fast burst secretion from the amplitude and time constant of slow burst secretion. None of the parameters were significantly different between groups. H, Scaled version of the mean capacitance traces in A clearly show similar kinetics in the three groups. Overexpression levels of Syt1 constructs were similar (see Fig. 1). Error bars indicate SEM.