Role of serotonin in the digestive system, artwork. In the gut serotonin (5HT) is produced by enterochromaffin (EC) cells, which are found in the epithelial lining, in response to the presence of food in the lumen. Serotonin acts locally, on the digestive tract, and also on the central nervous system (CNS). Local effects include activating peristalsis and secretory cells. Actions on the CNS include transmitting feelings of abdominal discomfort and bloating, and fullness.