Responses to colorectal distension. A: visceromotor responses to distension did not differ between C57BL/6 and glial cell line-derived neurotrophic factor family receptor α-3 (GFRα3) knockout (KO) mice [F(1,112) = 1.07, P = 0.304]. Relative to intracolonic treatment with saline (B), 2,4,6-trinitrobenzene sulfonic acid (TNBS, C) significantly increased visceromotor responses to distension on all days of testing [TNBS, n = 6, F(4,20) = 6.32, P = 0.002]. Responses to distension in saline-treated mice were slightly, but significantly, increased on day 10 of testing relative to baseline [saline, n = 7, overall F(4,24) = 5.37; Holm-Sidak post hoc test, t = 4.58, P < 0.05]. Data are expressed as means ± SE of responses normalized to the pretreatment baseline response to 60 mmHg. D: areas under the stimulus-response curves (AUC) derived from the data presented in B and C. Visceral hypersensitivity produced by TNBS significantly differed in magnitude across days after treatment [F(1,44) = 8.09, P = 0.0160].