Fig. 2.
Effects of α2-adrenergic receptor (AR) antagonists on dexmedetomidine (DEX) inhibition of synaptic vesicle (SV) exocytosis. (Top) Schematic diagram of protocol to test the effect of DEX on synaptophysin-pHluorin (syn-pH) fluorescence in the presence of α2-AR antagonists. Filled boxes indicate electrical stimulation at 10 Hz for 20 sec. (A, Top) Time series of fluorescence changes in the absence (control; CTL) or presence of DEX applied for 7 min, shown every 2.5 s, normalized to total pool (TP) before and after stimulation (horizontal bar). (Bottom) Mean effect of 0.1 μM DEX on SV exocytosis at 10 s of stimulation (DEX 57 ± 6% of control). Data are expressed as mean ± SEM. **P < 0.01 by two-tailed paired t test (n = 9). (B–D) Effects of α2-AR antagonists on action potential (AP)–evoked SV exocytosis at 10 s of stimulation (boxes). (Top) Fluorescence changes (ΔF) with time before and after stimulation. Fluorescence intensities normalized to TP, with data shown every 2.5 s. (Bottom) ΔF at 10 s of stimulation. Data are expressed as mean ± SEM. ***P < 0.001; ns, not significant by one-way repeated measures ANOVA followed by Tukey multiple comparison test.