Time course of the development of cold-evoked behaviours after mental nerve injury. Bilateral grooming evoked by cold stimulation (topical ethyl chloride) of the chin was significantly increased 11 days after chronic constriction injury (CCI) of a mental nerve (A), but not after partial tight ligation of the nerve (PTL; B) or sham operation (C). 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 < 0.002; 2-factor repeated measures ANOVA followed by Tukey’s test post-hoc). CCI, n = 22; PTL, n = 19; Sham, n = 17.