Effect of prokineticin 2 on nociceptive responses to injection of acetic acid in rats. Intraplantar injection acetic acid evoked a flinch/shaking response in the presence of the TRPV1 inhibitor capsazepine (100 μM). The pretreatment of PK2 increased flinching behavior induced by acetic acid in dose-dependent manner. The effect of PK2 was blocked by PKRA (10 nM), a PK2 receptor antagonist. Flinching or shaking of the paw was recorded as the number of flinches per observation period (5 min). **P <0.01, post hoc Bonferroni’s test, compared with control; #
P <0.05, post hoc Bonferroni’s test, compared with PK2 (3nM) column. n = 10 per each column. PKRA: prokineticin 2 receptor antagonist; PK2: prokineticin 2; TRPV1: transient receptor potential vanilloid receptor-1.