Fig. 4

Repeated mTBIs produced robust increases in mechanical allodynia and grimace scores. Hypersensitive hindpaw withdrawal to tactile stimulus, ipsilateral to injured hemisphere (A, left hindpaw) and contralateral to injured hemisphere (B, right hindpaw), at 24 h after each injury and 3 days, 1 week, 1 month and 2 months after third injury. Statistically significant loss in response threshold (i.e., more pain) when compared with baseline and sham after each injury and sustained up to 2 months (n = 10/group; ***p < 0.001, repeated-measures ANOVA, Tukey’s HSD). C, D Mouse grimace score (MGS) was assessed at baseline, 24 h after each injury, 3 days and 1 week in either sham animals (C) or injured animal group (D). No significant change in MGS was observed in the sham group; conversely, statistically significant increase in MGS (i.e., more pain) was determined at 24 h after each injury when compared with baseline. Increased MGS was sustained up to at least 1 week after the last injury (n = 7/group; *p < 0.05 **p < 0.01, ***p < 0.001, repeated-measures ANOVA, Tukey’s HSD)