Voltage-gated Ca²⁺ channel subtypes contributing to modulation of exocytosis by dexmedetomidine. (A) Effect of 0.1 μM dexmedetomidine (DEX) on exocytosis in the presence of the selective N-type, voltage-gated Ca²⁺ channel (VGCC) antagonist ω-conotoxin GIVA (Cono, 1 μM). (Top) Schematic diagram of protocol. (Middle) Time series of fluorescence changes with stimulation at 10 Hz for 20 s. Fluorescence was normalized to TP with data shown every 2.5 s. (Bottom) Mean amplitudes of synaptophysin-pHluorin (syn-pHy) responses at 10 s of 10-Hz stimulation normalized to control (CTL; n = 7). (B) Effect of 0.1 μM DEX in the presence of the specific P/Q-type VGCC antagonist ω-agatoxin IVA (Aga, 0.4 μM). (Top) Schematic diagram of protocol. (Middle) Time series of fluorescence change with 20-s stimulation at 10 Hz. Fluorescence was normalized to TP with data shown every 2.5 s. (Bottom) Mean amplitudes of syn-pH responses at 10 s AP of 10-Hz stimulation normalized to control (n = 8). Data are expressed as mean ± SEM. *P < 0.05, ***P < 0.001 by one-way repeated measures ANOVA followed by Tukey multiple comparison test.