Fig. 1.
5-HT2B mediates 5-HT-induced mechanical hyperalgesia through phospholipase Cβ (PLCβ) and protein kinase Cε (PKCε). a Wild-type CD1 mice (8–12 weeks old) were intraplantarly injected with different doses of 5-HT2B antagonist (RS127445 (RS)) before 5-HT injection. Mechanical tests were performed and the threshold of paw withdrawal (PWT) was measured at 30 min. Data are mean ± SEM PWT of total tested mice (n ≥ 6 per group). Comparisons between inhibitor-injected groups and inhibitor-uninjected groups were done by one-way ANOVA with a post hoc Bonferroni test. ***p < 0.001. b Mice were intraplantarly injected with 25 μl of different doses of PKA inhibitor (PKAI; H89) or PKCε inhibitor (PKCεI; TAT-PKCεV1–2) before 5-HT injection. The PWT was measured at 30 min (for PKAI) or 60 min (for PKCεI) after 5-HT injection. Inhibitor-injected groups were compared with inhibitor-uninjected groups by one-way ANOVA with a post hoc Bonferroni test. ***p < 0.001. c Mice were injected with 5-HT, followed by mechanical tests at different times. Ipsilateral PWTs were compared with contralateral PWTs by two-way ANOVA with a post hoc Bonferroni test. ***p < 0.001. d Mice were pre-injected with RS (20 μM) before 5-HT injection, followed by mechanical tests at different times. Comparisons between the ipsilateral PWTs of 5-HT-injected and RS/5-HT-injected animals were done by two-way ANOVA with a post hoc Bonferroni test. ## p < 0.01; ### p < 0.001. e Mice were pre-injected with PKCεI (50 μM) or PKAI (50 μM) before 5-HT injection. PWT for ipsilateral paw was measured at different times. The ipsilateral PWTs of 5-HT/inhibitor- were compared with the ipsilateral PWTs of 5-HT-injected animals by two-way ANOVA with a post hoc Bonferroni test. ## p < 0.01; ***p < 0.001; ### p < 0.001. f Mice were pre-injected with AC inhibitor (SQ22536 (SQ), 1 mM), Gi inhibitor (pertussis toxin (PTX), 4 ng/μl) or PLCβ inhibitor (U73122, 500 μM) before 5-HT injection. PWT for ipsilateral paw was measured at different times. Comparisons between ipsilateral PWTs of 5-HT/inhibitor- and ipsilateral PWTs of 5-HT-injected animals (number sign), were done by two-way ANOVA with a post hoc Bonferroni test. ### p < 0.001