Mechanical sensitivity after nerve injury. 50% withdrawal threshold differences between operated and non-operated sides were significantly different 21 days after chronic constriction injury (CCI) of the mental nerve, but not after partial tight ligation (PTL) or sham operation. The operation was performed on day 0 (indicated by the dashed line). Symbols are mean ± 1 S.E.M. Asterisk indicates significant differences between ipsilateral and contralateral sides (P < 0.003; 2-factor repeated measures ANOVA followed by Tukey’s test post-hoc).