Interaction Between Intestinal Serotonin and The Gut Microbiome

Greater than 90% of serotonin (5-HT) in the human body is derived from Enterochromaffin (EC) Cells located within the most distal portion of the gastrointestinal tract. Inside of the large intestine can be found a population of trillions of symbiotic microbes. Current evidence shows that these microbes influence host physiology through communication with the nervous system via metabolic byproducts. In the colonic environment, 5-HT is an important signaling molecule for peristalsis, enteric motor and secretory reflexes, and immune responses. 5-HT synthesis within the colon is regulated by host microbiota through stimulation of EC from their short chain fatty acid by products. EC have been shown to release 5-HT into the colonic lumen after stimulation from various non-microbially produced products such as bile acids, allyl isothiocyanate, catecholamines, and tryptamine. Irregular 5-HT signaling has been shown to influence microbial colonization of the colon. Further exploration is necessary to understand the complete mechanism of microbial signaling and colonic 5-HT production.