Tryptamine is a selective, blood-brain-penetrating 5-HT4 receptor agonist (EC50=1-3 mM) and an endogenous ligand of the aryl hydrocarbon receptor (AHR) (Kd=10-50 nM). Tryptamine promotes intestinal anion secretion and fluid transport by activating G protein-coupled receptors (GPCRs) and accelerates gastrointestinal motility. Tryptamine regulates Th17/Treg balance to inhibit neuroinflammation, competitively binds to 5-HT receptors to regulate central nervous system activity, and participates in temperature regulation and spinal reflex regulation as a neuromodulator. Tryptamine can be used to study intestinal motility disorders such as functional constipation, and has shown significant efficacy in multiple sclerosis models[1][2][3].