Fig. 1. Neutralization of interleukin (IL)-10 protein expression by anti-IL-10 antibody in amitriptyline/morphine coinfused rats. (  A ) IL-10 protein level was measured in the different groups (n = 4 of each group). Coadministration of amitriptyline significantly increases IL-10 expression in morphine-infused rats; anti-IL-10 antibody neutralizing the IL-10 expression induced by this combination. One-way analysis of variance (ANOVA) revealed significant differences among the six groups (F(5,18) = 24.35,  P < 0.001). ***  P < 0.001 as compared with saline-infused group; ###  P < 0.001 as compared with morphine-infused group, +++  P < 0.001 as compared to the amitriptyline/morphine coinfused group. (  B ) Spinal cords were fixed and double-labeled with FITC-labeled anti-CD11/OX42 (microglia,  green fluorescence ) and rhodamine-labeled goat anti-IL-10 antibody (  red fluorescence ). Coincidence of the two labels is seen in  yellow (  white arrows ) (n = 4 of each group). The  scale bar represents 20 μm. CONT = saline infusion; CONT+AMI = saline plus amitriptyline coinfusion; CONT/Anti-IL-10Ab = saline infusion plus anti-IL-10 antibody injection for 5 days; FITC = fluorescein isothiocyanate; MO = morphine infusion; MO+AMI = morphine plus amitriptyline coinfusion; MO+AMI/Anti-IL-10Ab = morphine plus amitriptyline coinfusion plus anti-IL-10 antibody injection for 5 days.