some more in depth info on this
altered serotonin signaling and ibs compilation
"The Trusted Source
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Harold J. DeMonaco, M.S.
Harold J. DeMonaco, M.S., is senior analyst, Innovative Diagnostics and Therapeutics, and the chair of the Human Research Committee at the Massachusetts General Hospital. He is author of over 20 publications in the pharmacy and medical literature and routinely reviews manuscript submissions for eight medical journals.
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June 19, 2001
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A:
Irritable bowel syndrome is now recognized as a disorder of serotonin activity. Serotonin is a neurotransmitter in the brain that regulates sleep, mood (depression, anxiety), aggression, appetite, temperature, sexual behavior and pain sensation. Serotonin also acts as a neurotransmitter in the gastrointestinal tract.
Excessive serotonin activity in the gastrointestinal system (enteric nervous system) is thought to cause the diarrhea of irritable-bowel syndrome. The enteric nervous system detects bowel distension (expansion) on the basis of pressure-sensitive cells in the bowel lumen (opening). Once activated, these pressure-sensitive cells promote the release of serotonin, which in turn promotes both secretory function and peristaltic function (the contractions of the intestines that force the contents outward). At least four serotonergic receptors have been identified to be participants in the secretory and peristaltic response.
Patients with diarrhea-predominant IBS may have higher levels of serotonin after eating than do people without the disorder. This recognition led to the development of the first drug used specifically to treat diarrheal symptoms of IBS, alosetron (also known as Lotronex). Alosetron blocked the specific serotonin receptors responsible for recognizing bowel distention. In doing so, it blocked the effects of serotonin and reduced both bowel secretions and peristalsis. Constipation was the most common side effect seen. (Note: Alosetron was removed from the market by the manufacturer after repeated reports of a dangerous condition known as ischemic colitis became known.) Tegaserod (Zelmac) is another drug under development and under review by the U.S. Food and Drug Administration for approval. Tegaserod is indicated for the treatment of constipation-predominant IBS and works to increase enteric nervous system serotonin activity.
So, increasing serotonin activity in the enteric nervous system produces increased bowel secretions and peristalsis (and potentially diarrhea), whereas depressing serotonin activity produces reduced secretions and reduce peristalsis (and potentially constipation). Increasing serotonin activity in the brain would increase awareness and, in higher doses, produce anxiety, insomnia and restlessness."
However, the mechanisms are not fully understood because its so complex and other factors are also very important in IBS.
But this has in part explain why there is abnormal motility in IBS the D and c and d/c, that there is a problem in serotnin singaling in the gi tract. The cells that store the majority of it in the gi tract, EC cells or enterochromaffin cells.
http://www.ibsgroup.org/forums/index.php?s=a21835d0d15f82b5a3f66fbed9d06658&showtopic=80198&st=0&p=707965&#entry707965
There is a lot more to all this in the link
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My website on IBS is www.ibshealth.com
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