Co-application of capsaicin and QX-314 attenuates gut hypersensitivity induced by dinitrobenzene sulfonic acid (DNBS) in a rodent model of colitis. (A) The experimental setup. A colorectal balloon connected to a barometer is inserted into the rat’s colon. Abdominal withdrawal reflexes (AWRs) are defined as an enhanced back kyphosis and neck extension and are measured following colorectal distension resulting from applying either 40 mm Hg (colitis model) or 60 mm Hg (naïve rats). (B) Box plot and individual values of the number of AWRs following colorectal distension at 40 mm Hg in the same rats (color-coded) before and 4 days after treatment with DNBS (colitis) and 4 days after DNBS but treated with an intrarectal co-application of 1 mg/mL capsaicin and 20 mg/mL QX-314 (2%). Note that treatment with DNBS significantly increases gut sensitivity, which was reversed to control values by treatment with capsaicin and QX-314. n = 9 rats in each group. Repeated-measures 1-way analysis of variance with post hoc Bonferroni. The box plot depicts the mean and 25% to 75% percentiles, and the whiskers depict 1.5 SD. ***P <.001; ****P <.0001.