SLC6A4 and Constipation: Gray-scale analysis results showed that the SERT mRNA level and relative expression in Caco-2 cells of mice in the constipation group were significantly higher than those in the distilled water group, the 5-HT level was lower than the distilled water gavage group, and the 5-HT expression on the surface of the biofilm-positive colon tissue was higher than that of the biofilm-negative colon tissue.