Fig. 3.

Effects of PF and MK-801 on formalin-induced licking and biting behavior in mice. a: represents early phase (0–5 min) and b represents late phase (10–30 min) of formalin-induced nociception. PF (100, 200, 500 nmol, i.c.v.) was administered 15 min before intraplantar injection of 20 μl 1 % formalin. MK-801 (pmol, i.t.) was injected 5 min before intraplantar formalin injection. The control group received ACSF. Total time of each mouse spent on licking and biting of the injected paw was recorded. Data represents mean ± S.E. (n = 12). ^*** p < 0.001 compared with the control group; ^### p < 0.001 compared with the MK-801-treated group, respectively