2.8. Arachidonic Acid-Induced Mouse Algesic Model

To test whether AQCA is able to ameliorate algesic property induced by arachidonic acid, as reported previously [19, 20], ICR mice (n = 7) were orally pretreated with AQCA (3 and 30 mg/kg) or indomethacin (5 mg/kg) for 7 days. After the final treatment, arachidonic acid (2% (w/v)) was applied to the ear of the mouse (25 μL/ear) as described previously [21]. The thickness of the oedema was measured with a constant-pressure thickness gauge 1 h after treatment with arachidonic acid. To evaluate hypoalgesic efficacy, the inhibitory effect of AQCA on ear oedema was calculated as follows:

where D_ET is ear thickness of drug-treated group, N_ET is ear thickness of normal untreated group, and C_ET is ear thickness of control group.