Figure 10.

The RRP of vesicles is larger at high temperature. A, The paired pulse protocol used to calculate the maximum size of the RRP was composed of two 100 ms pulses with a 25 ms interval. The second pulse was depolarized to −30 mV. The first pulse was adjusted to give the same total amount of Ca²⁺ influx (Q_Ca) as the second pulse. It was different from cell to cell. In this example, the first depolarizing potential was −38 mV. The intervals between pulse pairs was 60–90 s to allow for full recovery. Ca²⁺ current recorded at 23°C and 31°C is shown in black and red, respectively. ΔC₁ and ΔC₂ are capacitance jumps triggered by the first and second depolarization, respectively. B, The maximum size of the RRP was calculated according to B_max = $\frac{\Delta C_1+\Delta C_2}{1-{\left(\Delta C_2/\Delta C_1\right)}^2}$. The value of B_max increased significantly from ∼83 fF (n = 4) at 23°C to 246 fF at 31°C (n = 7, p = 0.0351, unpaired t test). C, The Ca²⁺ influx during the first and second depolarizing pulses was 31.8 ± 6.8 pC and 31.7 ± 6.8 pC at room temperature (n = 4, p = 0.93), whereas the Ca²⁺ influx during the first and second pulses was 62.8 ± 3.8 pC and 63.3 ± 3.1 pC at high temperature (n = 7, p = 0.69). Both the first (p = 0.0005, unpaired t test) and the second (p = 0.0002, unpaired t test) pulses thus triggered more Ca²⁺ influx at high temperature. *p < 0.05, **p < 0.01, ***p < 0.001.