HTR5A and colitis: Accordingly, mice lacking 5-HT re-uptake transporter (SERT) exhibited exacerbation of chemically and genetically induced colitis (Bischoff et al., 2009); conversely, a lower damage was reported in mice with reduced availability of gut 5-HT, through genetic deletion or pharmacological inhibition of Tph1 (Ghia et al., 2009; Margolis et al., 2014; Kim et al., 2015).