Xylene-induced ear edema in mice

Mice (n=48) were randomly divided into six groups (n=8), as follows: Vehicle control [sodium CMC]; 250 mg/kg, 500 mg/kg, 1,000 mg/kg and 2,000 mg/kg AP ethanol extract; and 5 mg/kg dexamethasone. AP ethanol extract and dexamethasone were administered by gastric perfusion once daily for 3 days. The vehicle control group was administered an equivalent volume of 2.5% sodium CMC solution. Xylene (10 µl) was added dropwise onto the anterior and posterior surfaces of the right ear 4 h after gastric perfusion on the third day, while the left ear was used as a control. Mice were sacrificed by cervical dislocation 2 h after xylene application. Subsequently, both ears of the mice were removed, and ear disks measuring 9 mm in diameter were punched using a cork borer (YLS-25A; Jinan Yiyan Biotechnology, Jinan, China) and weighed. The extent of edema was evaluated by the weight difference between the right and the left ear disks of the same animal, according to the following formula:

where w indicates weight of the ear.