Figure 2: Effects of 5-HT7 receptor agonists AS-19 (a), E-57431 (b), and E-55888 (c) on formalin-induced nociceptive behaviors during phase II in wild-type and 5-HT7 receptor knockout mice. Subcutaneous administration of AS-19 (10 mg/kg), E-57431 (10 mg/kg), and E-55888 (20 mg/kg) significantly reduced the licking/biting time of the hind paw injected with formalin in wild-type but not in 5-HT7 receptor knockout mice. Each bar represents the mean ± S.E.M. (–12). *** versus vehicle corresponding group; ## versus corresponding dose in 5-HT7 receptor knockout mice (Bonferroni multiple comparison test after ANOVA).