HTR5A and irritable bowel syndrome: Zhu et al. (2018), for instance, discovered that Trinitrobenzene Sulfonic (TNBS)-induced colon EC cells of IBS rats exhibit proliferation, and abnormally high expression of 5-HT, and Tryptophan Hydroxylase (TPH). This process was significantly reversed by EA stimulation of ST25 and Zhongwan (CV12). Additionally, the process significantly increased 5-Hydroxyindoleacetic acid (the main metabolite of 5-HT) concentration. In other words, EA stimulation can reduce and promote production and rapid metabolism of 5-HT, respectively (Zhu et al., 2018).