SLC6A4 and irritable bowel syndrome: As shown in Figure 4, the intensity of SERT immunoreactivity in colonic mucosa of PI-IBS rats was significantly decreased when compared to that of the control (40.3 ± 3.1 versus 49.0 ± 3.2; P < 0.05), suggesting that TNBS-induced PI-IBS rats also has the decreased SERT expression in the colon.