Results are expressed as the number of scratching events for the indicated time periods. (A and B) Spontaneous scratching in untreated mice. (A) Frequency of spontaneous scratching events during 30-minute intervals over 120 minutes of recording. (B) Frequency of spontaneous scratching events per 60 minutes, averaged over 120 minutes of recording. Tgr5-Tg mice exhibited increased frequency of spontaneous scratching compared with Tgr5-WT and Tgr5-KO mice. (C) Vehicle control (0.9% NaCl, intradermal to the nape of the neck) did not stimulate scratching, although scratching was generally more frequent in Tgr5-Tg mice. (D) DCA (25 μg, intradermal) robustly stimulated scratching in Tgr5-WT mice, and scratching was exacerbated in Tgr5-Tg mice and suppressed in Tgr5-KO mice. (E) DCA (5–25 μg) stimulated dose-dependent scratching in Tgr5-WT mice. (F and G) TLCA and OA (25 μg) stimulated scratching in Tgr5-WT mice, which was markedly attenuated in Tgr5-KO mice. (H) UDCA (25 μg) had a small stimulatory effect that was not different among Tgr5-Tg, Tgr5-KO, and Tgr5-WT mice. (I) Histamine (50 μg) stimulated scratching to a similar extent in Tgr5-Tg, Tgr5-KO, and Tgr5-WT mice. (J) Summarized results showing the frequency of scratching events during the first 60 minutes after injection. *P < 0.05, **P < 0.01 vs. Tgr5-WT; #P < 0.05 vs. 5 μg DCA; ANOVA and Student-Newman-Keuls post-hoc test. n is indicated.