Reduced capsaicin-induced mechanical hypersensitivity in hph mice, but normal spontaneous pain behaviours. (a) Spontaneous pain responses; total time licking, biting and lifting the paw during 10 min after capsaicin injection (1 μg/paw). No difference was found between hph mice and WT mice (p = 0.46, n = 7–8). (b) Onset of pain behaviour. No differences in latency time was seen among genotypes (p = 1.00, n = 7–8). Mann–Whitney t-test, two-tailed. (c) von Frey time course; after capsaicin injection (1 μg/paw) both WT mice and hph mice developed mechanical hypersensitivity (n = 6–10). WT: ***p < 0.001 and hph: †††p < 0.001 versus baseline values. Two-way RM-ANOVA with pair-wise comparisons using the Fisher’s LSD test. (d) Area under curve analysis. A statistical significant difference in mechanical hypersensitivity between hph mice and WT controls was found (#p = 0.04). Mann–Whitney t-test, two-tailed. Data are presented as mean ± or + SEM.