Figure 7. Voltage dependence of exocytosis in β-cell.

A, capacitance increases (bottom) elicited by 500-ms depolarizations (top) from −70 mV to −40, −20, 0, +20 and +40 mV. The voltages during the depolarizations are indicated to the right of the respective capacitance traces. B, capacitance increase (ΔC) displayed against the voltage during the depolarizing pulses (V). Data are mean values ±s.e.m. of 32 experiments. The right hand axis indicates the exocytosis normalized to the response observed at 0 mV. The dotted lines indicate amplitude of exocytosis measured at −20 mV, which corresponds to the peak of the action potential (see Discussion). C, peak Ca²⁺ current amplitude (I) displayed against voltage during depolarization (V). Note that the current amplitude is maximal between 0 and +10 mV and that the current reverses at (+60 mV. Data are mean values ±s.e.m. of 20 experiments.