Lowered mechanical threshold of whisker pad after induction of TIC. (A) Mechanical threshold was determined for the whisker pad with von Frey filaments before and after infraorbital nerve traumatic compression on day 3 and 7 in the first week, and once a week for the subsequent 9 weeks. The data presented is the 50% mechanical threshold in gram force. Mice had statistically significant decreases in mechanical threshold 3 days after surgical placement of chromic gut suture compared to the sham operated group as well as to the contralateral side, (one-way ANOVA, ***p < 0.001). The continuous mechanical allodynia persisted for 10 weeks. (B) Administration of acetone onto the ipsilateral whisker pad elicits a cold allodynia-like response (4 wk). The mice with TIC injury had an increased rubbing/scratching duration time compared to the control mice. *p < 0.05.