Fig. 4.

Effect of opioid receptor antagonists on PECN–induced antinociception assessed using the acetic acid–induced abdominal constriction test in mice. β–funaltrexamine (β–FNA; 10 mg/kg, i.p.), naltrindole (NALT; 1 mg/kg, i.p.), or nor–binaltorphimine (nor–BNI; 1 mg/kg, i.p.) were administered 90 min, 15 min and 30 min respectively, before oral administration of vehicle (10 mL/kg), or PECN (500 mg/kg). Each column represents the mean ± SEM of six mice. Statistical analyses were performed using one–way ANOVA followed by Dunnett’s post hoc test. ^** p < 0.01, ^*** p < 0.01compared to control group. ^### p < 0.001 compared to 500 mg/kg PECN–treated group