Fig. 1. Effect of an intraplantar injection of complete Freund's adjuvant (CFA) on spontaneous pain-like behaviors in wild-type (+/+) and prodynorphin (PDYN) knockout (−/−) mice. Immediately after intraplantar injection, the number of flinching (A-i ) or licking (A-ii ) behaviors was counted, and the total duration of flinching and licking behaviors was measured (B ) for 20 min after the injection of CFA into the right hind paw of mice. Each point indicates the mean ± SEM of 3–5 mice. Bonferroni test: ***P < 0.001, wild-type mouse with intraplantar injection of saline versus  wild-type mouse with intraplantar injection of CFA; $$ P < 0.01, $$$ P < 0.001, wild-type mouse with intraplantar injection of CFA versus  PDYN knockout mouse with intraplantar injection of CFA.