Irritable Bowel Syndrome Message Boards

excessive levels of serotonin could cause symptoms of diarrhea?

In the GI tract the predominant site of serotonin synthesis, storage, and release is the enterochromaffin cells of the intestinal mucosa. Within the intestinal mucosa, serotonin released from enterochromaffin cells (EC cells) activates neural reflexes associated with intestinal secretion, motility, and sensation. The excessive levels of serotonin come from the EC cells and are not determined by levels in the blood or other body tissue. Ingestion of 5-HT has little effect on the serotonin levels released from EC cells. Generally speaking dietary approaches have little effect on serotonin levels released from EC cells.

However, ingested serotonin or l-tryptophan may effect the levels of melatonin in the GI tract. There is hundreds of times more melatonin in the GI tract than is involved in promoting sleep in the brain. Melatonin in the GI tract is produced from serotonin in the GI mucosa in serotonin-rich enteroendocrine cells. Melatonin plays a role GI motility and sensitivity possibly by blocking nicotinic channels or Ca2+ activated K+ channels. Oral ingestion of 5-ht and 5-htp are known to effect the levels of melatonin in the GI tract. The levels of melatonin in the GI tract increase with food intake particularly with high intake of dietary tryptophan. Oral administration of melatonin is known to affect colonic transit time in IBS & healthy individuals and reduce pain in IBS individuals. It does not effect sleep. I have been experimenting with melatonin to control IBS pain with good results. For the first time in more than 20 years after trying a variety of drugs I have been relatively pain free for over 2 months using melatonin.

For a complete description of how serotonin works in the GI tract see Serotonin and Its Role in Colonic Function and in Gastrointestinal Disorders. For a discussion of the role of melatonin in IBS see Is Melatonin Involved in the Irritable Bowel Syndrome?

Sleep disturbances are known to occur in IBS. This article in GUT titled Sleep and gastric function in irritable bowel may be of interest to you. They find that during REM sleep in patients with IBS and have documented alterations in normal gastric functioning during sleep.

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STABLE: ♂, IBS-D 50+ years - Science of IBS

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