Dysbindin deficiency produces a smaller RRP size of LDCVs in chromaffin cells. (A) Comparison of the kinetics of vesicle endocytosis in WT and sdy chromaffin cells. The cell was stimulated by a 200-ms depolarization from −70 to +10 mV. Depolarization-induced capacitance changes (ΔC_m) were larger in WT cells than in sdy cells (P < 0.001). The kinetics of endocytosis in sdy cells was similar to that in WT cells (P > 0.05). n = 7 (WT) and 6 (sdy). (B) Use of a dual-pulse protocol for estimating RRP size. Example of the capacitance responses (top) and Ca²⁺ currents (bottom) to a dual pulse. Two depolarizations with a 100-ms interval were applied. The depolarizing potentials were adjusted to give a similar amount of Ca²⁺ influx. (C) Comparison of the RRP size in WT (548.6 ± 92.3 fF) and sdy (287.0 ± 48.5 fF) cells, which were markedly different. n = 10 (WT) and 13 (sdy). (D) Comparison of the refilling kinetics of the RRP in WT and sdy cells. Normalized RRP size values were plotted versus the interpulse interval. Data points up to 10 s were fitted by a monoexponential curve. The interval between pulse pairs was ∼60 s. The time courses of RRP recovery were not significantly different. n = 10 (WT) and 13 (sdy). *, P < 0.05. Error bars indicate the mean ± SEM.