Figure 1: Nociceptive behavior of wild-type and 5-HT7 receptor knockout mice in the tail flick and tail immersion tests (a), hot plate 55°C test (b), and formalin test (c). Both genotypes showed similar latency for all measured behaviors in the tail flick, tail immersion, and hot plate tests. Formalin-induced licking and biting of the hind paw injected with formalin in 5-HT7 receptor knockout mice did not significantly differ from those in wild-type mice either in phase I (0–5 min) or in phase II (15–45 min). Only a slight but not significant increase of the licking/biting time was observed 25 min after formalin injection in 5-HT7 receptor knockout mice compared to wild-type mice. Each bar or symbol represents the mean ± S.E.M. (–12 per group). Forepaw licking: FPL; hindpaw licking: HPL. No significant differences were observed in thermal nociception (unpaired Student’s -test) or formalin-induced nociceptive behaviors (Two-Way ANOVA).