Figure 2. Effect of EEB of H. umbrosa on the acetic acid-induced writhing test in the absence and presence of naloxone in mice. Vehicle (control), EEB (100, 200 and 400 mg/kg) or morphine (MOR) were administered p.o. 1 h before acetic acid injection. Pre-treatment with naloxone (NAL, 1.5 mg/kg, i.p.) was performed 0.5 h before treatment (i.p.) with EEB (400 mg/kg), or MOR (3 mg/kg). Each column represents mean ± S.E.M. (n = 6, per group). *p < 0.05 or ***p < 0.001 versus control. ###p < 0.001 versus MOR group (ANOVA followed by Tukey's test).
