Editing Serotonin (section)

====Digestive tract (emetic)====
Serotonin regulates gastrointestinal (GI) function. The gut is surrounded by [[enterochromaffin cell]]s, which release serotonin in response to food in the [[Lumen (anatomy)|lumen]]. This makes the gut contract around the food. Platelets in the [[Hepatic portal system|veins draining the gut]] collect excess serotonin. There are often serotonin abnormalities in gastrointestinal disorders such as constipation and irritable bowel syndrome.<ref name="ReferenceA">{{cite journal | vauthors = Beattie DT, Smith JA | title = Serotonin pharmacology in the gastrointestinal tract: a review | journal = Naunyn-Schmiedeberg's Archives of Pharmacology | volume = 377 | issue = 3 | pages = 181–203 | date = May 2008 | pmid = 18398601 | doi = 10.1007/s00210-008-0276-9 | s2cid = 32820765 }}</ref>

If irritants are present in the food, the enterochromaffin cells release more serotonin to make the gut move faster, i.e., to cause diarrhea, so the gut is emptied of the noxious substance. If serotonin is released in the blood faster than the platelets can absorb it, the level of free serotonin in the blood is increased. This activates [[5-HT3 receptor]]s in the [[chemoreceptor trigger zone]] that stimulate [[vomiting]].<ref>{{cite book | vauthors = Rang HP |title=Pharmacology |publisher=Churchill Livingstone |location=Edinburgh |year=2003 |page=187 |isbn=978-0-443-07145-4}}</ref> Thus, drugs and toxins stimulate serotonin release from enterochromaffin cells in the gut wall can induce emesis. The enterochromaffin cells not only react to bad food but are also very sensitive to [[Radiation therapy|irradiation]] and [[chemotherapy|cancer chemotherapy]]. Drugs that [[5-HT antagonist|block 5HT3]] are very effective in controlling the nausea and vomiting produced by cancer treatment, and are considered the gold standard for this purpose.<ref>{{cite journal | vauthors = de Wit R, Aapro M, Blower PR | title = Is there a pharmacological basis for differences in 5-HT3-receptor antagonist efficacy in refractory patients? | journal = Cancer Chemotherapy and Pharmacology | volume = 56 | issue = 3 | pages = 231–238 | date = September 2005 | pmid = 15838653 | doi = 10.1007/s00280-005-1033-0 | s2cid = 27576150 }}</ref>