Figure 3.
Reversible events mirror repetitive fusion of single vesicle. ai, The distributions of vesicle membrane capacitance (Cv) amplitudes of reversible events from a representative patch, before and after the stimulation with dbcAMP, were similar. Lines show fitted Gaussian curves with means of 1.09 ± 0.05 fF (control, correlation coefficient r = 0.92; n = 11 events) and 1.08 ± 0.01 fF (dbcAMP, r = 0.99; n = 64 events), respectively. aii, The relationship between amplitudes of the downward and the preceding upward Cv steps of reversible events: the regression line represents the best fit with parameters: y (Cv amplitude of the downward step) = (1.0 ± 0.1) × x (Cv amplitude of the upward step) + (−0.1 ± 0.1) (r = 0.95, n = 11 events) before stimulation and the regression line y (Cv amplitude of the downward step) = (0.8 ± 0.1) × x (Cv amplitude of the upward step) + (0.26 ± 0.10) (r = 0.76, n = 64 events) after the stimulation (open circles). The slopes of both regression lines were similar (p = 0.2). b, The relationship between the average Cv amplitudes of downward versus upward discrete steps of reversible events in distinct membrane patches before and after the addition of cAMP-increasing agents. The solid line represents linear fit of the controls: y (the average Cv amplitudes of downward steps) = (0.97 ± 0.04) × x (the average Cv amplitudes of upward steps) + (−0.03 ± 0.15) (r = 0.99, n = 9 cells), and the hyphenated line represents linear fit to the data obtained after the addition of cAMP-increasing agents: y (the average Cv amplitudes of upward steps) = (1.04 ± 0.02) × x (the average Cv amplitudes of downward steps) + (−0.03 ± 0.05) (r = 0.99, n = 16 cells). The slopes of both regression lines were similar (p = 0.3). Values are mean ± SEM. c, Distribution of Cv amplitudes of all events in control conditions shows two population best fitted with Gaussian curves with means: 0.58 ± 0.01 fF (r = 0.82) and 1.44 ± 0.02 fF (r = 0.80), each corresponding to 50% of all events in control conditions. After dbcAMP, we only observed one population best fitted with Gaussian curve with mean 0.61 ± 0.01 fF (r = 0.99) that represents 93% of all events after dbcAMP.