5.6.2. Carrageenan-Induced Paw Edema Model

According to the previous protocol [50], the adult male rats were randomly divided into control group, carrageenan group, positive drug group (indomethacin), DKK-SP1 groups (2, 1, 0.5 mg/kg), with 12 rats in each group. DKK-SP1 and indomethacin were diluted with normal saline into each dose. The DKK-SP1 groups were intravenously injected DKK-SP1 (2, 1, 0.5 mg/kg) and the positive drug group was established by intraperitoneal injection of indomethacin (10 mg/kg). The control group and carrageenan group were intravenously injected with normal saline. After 1h, carrageenan (1%, 0.1 mL; except for the control group) was injected into the left hind paw pad. After injection of carrageenan for 0, 1, 2, 3, 4 and 5 h, the paw volumes were measured and recorded with a vernier caliper. After the final recording, the rats were anesthetized with ether and sacrificed, the hind paw and DRG were taken and stored in liquid nitrogen.

Paw swelling rate (%) = (paw volumes at each time point after carrageenan administration − paw volumes before administration)/paw volumes before administration) × 100%