Fig. 1

PACAP38-MrgprB2 pathway mediates stress-induced headache behaviours. a Facial mechanical withdrawal thresholds at consecutive time points after restraint stress (1 h/day for 3 days) and PACAP38 dural injection (0.1 ng) in wild-type (WT) or MrgprB2-deficient (KO) mice (n = 5 WT CON, 6 WT STR, and 9 KO STR mice). b Blood concentration of PACAP38 (n = 6 mice per group). Blood was collected immediately after cessation of stress or 24 h after stress. c β-hexosaminidase release by mouse peritoneal mast cells (n = 6 wells per group). d Facial mechanical withdrawal thresholds after dural injection with PACAP38 (1 ng) or IL-6 (0.1 ng) in WT or KO mice (n = 7 WT Veh, 7 WT PACAP, 5 WT IL-6, 6 KO Veh, and 6 KO PACAP mice). e Grimace score (n = 6 mice per group). (right) Representative mouse facial expression images. CON: control, C48/80: compound 48/80, STR: stress, IL-6: interleukin-6, Veh: vehicle. Significance comparisons: (a) *WT STR vs. WT CON; ⁺WT STR vs. KO STR; (d, e) *WT Veh. vs. WT PACAP38; ⁺WT PACAP38 vs. KO PACAP38. Error bars indicate S.E.M. *^/+p < 0.05; **^/++p < 0.01; ***^/+++p < 0.001; (a, d, and e) two-way ANOVA with Tukey’s multiple comparison post-hoc test; (b and c) one-way ANOVA with Tukey’s multiple comparison post-hoc test