Figure 5. Compensatory retrieval is accurate and reliable for large C_m jumps.

A, the magnitude of endocytosis vs. the C_m jump for single depolarizations (40-640 ms duration; symbol for each duration as indicated). Total endocytosis in femtofarads was determined from the amplitude of the best exponential fit to the C_m decay (A, or A₁+A₂; see Methods) whilst the C_m jump was calculated from the average across the first 10 capacitance points subsequent to the depolarization. Therefore some compensatory endocytotic responses are significantly larger than the C_m jump, because membrane added after the time used for C_m jump calculation was retrieved accurately (i.e. ⋄, 550 fF at exocytosis, 780 fF at endocytosis). Excess retrieval events (undershoot > 100 fF) were excluded from analysis. Inset, expansion of the region 0-100 fF. Many C_m jumps in this region were not accompanied by endocytosis (decay undetectable based on inability to be fitted by an exponential function). B, stimulus-evoked responses were sorted independently by (a) exocytosis (i.e. size of C_m jump) or (b) Ca²⁺ entry, and the percentage of responses accompanied by endocytosis was calculated for each bin.