Effect of intraplantar injection of prostaglandin E2 (PGE2) on mechanical sensitivity after the plantar incision. (A) After the plantar incision, the threshold against von Frey stimulation decreased immediately but returned to the same level as in naive animals by 14 days after the treatment. Intraplantar injection of PGE2 induced a reduction in the threshold against von Frey stimulation. Animals that received the plantar incision (incision 14 plus PGE2 group) developed prolonged mechanical hypersensitivity, which continued for 7 days after PGE2 injection, while naive animals treated with PGE2 (naive plus PGE2 group) developed transient mechanical hypersensitivity that lasted for less than 8 h. (B) PGE2 treatment 21 days after the plantar incision (incision 21 plus PGE2 group) also produced prolonged mechanical hypersensitivity compared to the transient mechanical hypersensitivity in naive animals treated with PGE2 (naive plus PGE2 group). Data are presented as mean ± SD. ****P < 0.0001 and *P < 0.05 versus naive plus PGE2 group (repeated two-way ANOVA); n = 6 per group.