Differences in visceral sensitivity between WT and TRPV1 KO mice in response to mechanical stimulation of the lower abdominal region. (A) Abdominal responses to Von Frey filaments in wild-type (WT) mice with vehicle instillations (N = 4). (B) Responses to pelvic stimulation in WT mice before and after intracolonic treatment with 2,4,6-trinitrobenzene sulfonic acid (TNBS) (N = 5). (C) Time course of the responses to mechanical stimulation of the lower pelvic area in transient receptor potential vanilloid 1 knockout (TRPV1 KO) mice before and after intracolonic instillations of the vehicle (N = 4). (D) Summary of the responses to pelvic stimulation recorded in TRPV−/− male mice during experimental colitis (N = 6). Presented data are mean percentages of response frequency (± SE) before (baseline) and at days 1, 2, and 3 post-treatment. ANOVA indicated a significant increase in response frequency in WT mice within 3 days post-TNBS treatment, whereas in KO mice the difference reached statistical significance only at days 2 and 3 after the induction of colonic inflammation.