Inhibition of the colon epithelium reduces visceromotor response (VMR) to colorectal distension (CRD). Inhibitory opsin archaerhodopsin (Arch) is conjugated to enhanced green fluorescent protein (EGFP) to enable visualization. Arch-EGFP (green) is specifically expressed in colon epithelial cells under the villin-cre driver (A) and not in the L6 DRG (B). C) A laser-balloon device was constructed to enable CRD simultaneous with light illumination of the colon lumen. D) VMRs to 60 mmHg CRD were recorded in villin-Archaerhodopsin (Vil-Arch) and control littermate mice before (Baseline) and during yellow light application (+ Laser). E) Comparing the effects of yellow light in Vil-Arch vs. control mice, there was a significant interaction between genotype and laser (p = 0.04; two-way ANOVA). Yellow light significantly reduced the VMR in Vil-Arch mice [n = 11 (7 male, 4 female); p = 0.01; Holm-Sidak test] but not in control littermate mice [n = 7 (4 male, 3 female); p = 0.97; Holm-Sidak test]. F) Out of 11 Vil-Arch mice, 8 displayed a significant decrease in VMR to CRD with the addition of yellow light. The mean of the baseline and the inhibited trials are shown. Inhibition occurred in an average of 71% of trials (inset). Scale bars = 100 μ;M (A), 50 μ;M (B).