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Fig. 1. Intraperitoneal (i.p.) injection of essential oil of Eucalyptus (EOE) reduced licking time in the second phase of the formalin test. Licking time in mice injected with control (0.9% saline, i.p.), vehicle (almond oil, i.p.), essential oil (11.25, 22.5, and 45 mg/kg, i.p.), or morphine (4 mg/kg, i.p.) 30 min prior to the injection of 20 μl of formalin (2% v/v) into the dorsal surface of their left, hind paws. Morphine, a positive control, reduced the licking time in the first phase (0–5 min). Meanwhile, EOE (45 mg/kg) and morphine significantly reduced licking time in the second phase (20–25 min). Each value represents the mean and standard error of mean. *P < 0.05, **P < 0.001 compared to the vehicle group. One-way analysis of variance followed by Tuckey’s post hoc test were performed for statistical analyses. The control group had 12 mice while the others had 8 mice.
Korean J Pain 2019;32:79~86
© Korean J Pain