Bonniei, Its is majorly complicated, but here you go. I posted once and lost all the information95 percent of the bodies serotonin is stored in the gi tract. IT is importantly used for the intiation of the peristaltic reflex. Contractions"Pathophysiology of IBSRecent advances have led to a greater understanding of the pathophysiology of irritable bowel syndrome (IBS). Clinical investigations have shown that both motor and sensory functions of the gut appear to be altered in patients suffering from IBS. The enteric nervous system, including 5-hydroxytryptamine (5-HT, serotonin), integrates and processes information in the gut, and is thought to represent a key element in the etiology of IBS.Alterations in motor and sensory functions may cause disturbances in GI motility and increased perception of visceral stimuli (visceral hypersensitivity), both of which make important contributions to the symptoms of IBS. Patients with visceral hypersensitivity are said to experience an exaggerated sensitivity to internal stimuli, such as painful distention in the small bowel and colon. These patients may also experience an increased perception of apparently normal motor events in the gut, resulting in a feeling of abdominal pain or discomfort.The role of serotonin in IBS symptomsApproximately 95% of serotonin (5-HT) is located throughout the GI tract. Serotonin has been shown to be involved in regulating motility, visceral sensitivity, and intestinal secretion.Growing evidence suggests that serotonin subtype 4 (5-HT4) receptors play an important role in the maintenance of GI motor function in humans. Activation of 5-HT4 receptors in the GI tract has been shown to stimulate the peristaltic reflex and intestinal secretion as well as inhibit visceral sensitivity."also important are 5ht3 receptors.This is also one reason why harmless foods can trigger symptoms. The cells are pressure sensitive to ALL stimuli and release serotonin when pressure is applied to them.In d ibs there is more secreted from gut cells and c less secreted. Then also alternating.very important cells are enterochromaffin cells and mast cells and endocrine cells in all this.The new drugs for IBS
http://www.aboutibs.org/Publications/serotonin.html It is very complex also and I am still learning about it all.It is also probably not the entire picture in IBS, but very important in the motility patterns and communication to the brain, among other things and the majority of IBS patients presenting to gastroenterologist, effectively demonstrate serotonin dysregulation."Researchers Identify Molecular Aberration in IBS PatientsCharlene LainoOct. 15, 2003 (Baltimore) � Significant alterations in serotonin signaling exist in the gastrointestinal tracts of IBS patients that do not appear in patients without IBS, according to new research. The findings shed light on gut motility, secretion, and sensation, as well as on the clinical manifestations of IBS, said Peter Moses, MD, associate professor of medicine and director of Clinical Research in the Digestive Diseases at the University of Vermont in Burlington. He presented the findings here Monday at the 68th annual scientific meeting of the American College of Gastroenterology. "We're showing a change at the molecular level in the gut," said co-investigator Gary Mawe, PhD, professor of anatomy and neurobiology at the University of Vermont. "Our finding that key elements of serotonin signaling are changed in IBS lends credibility to the notion that IBS is not all in patients' heads, but due to altered gut biochemistry and interactions between the gut and the brain." Researchers already knew that 95% of the body's serotonin (5-HT) is located in the gut and is primarily synthesized by and stored in endocrine cells, Dr. Moses said. That led them to suspect that alterations in serotonin may contribute to abnormal conditions in the gastrointestinal tract, leading to the development of pharmacologic agents that target 5-HT receptors, he said.While the drugs have proven effective in relieving symptoms of IBS, "no one has ever shown cause-and-effect," Dr. Mawe said. "The drugs were developed with the knowledge that serotonin affects gut motility and secretion, but what we didn't know is exactly how they were working." In their current research, the investigators have shown "a significant decrease in the serotonin transporter in cells that form the inner lining of the bowel" in patients with IBS, Dr. Mawe told Medscape. "In the gut, this transporter acts as a sponge to remove serotonin once it is released, and therefore stops its actions. But if you take the sponge away, serotonin that is released stays around longer, and this can lead to changes in motility, secretion, and sensitivity." For the study, the researchers examined tissue from 43 healthy controls, 32 patients with IBS, and 22 patients with inflammatory bowel disease. Each sample was evaluated using immunohistochemical staining, ELISA radioimmunoassay for serotonin content and release, and quantitative reverse transcriptase polymerase chain reaction for measurement of mRNA encoding. The researchers also measured serotonin content, the endocrine cell number, serotonin release, and presence of serotonin transporters (SERT). The study showed that samples from patients with IBS had significantly lower serotonin content � about 70 to 80 pM/mg of tissue compared with about 50 pM/mg in control patients (P .005). Patients with IBS also had significantly higher endocrine cell populations compared with control patients (P .005). Also, SERT mRNA and SERT immunoreactivity were markedly reduced, leading to a decrease in the capacity to remove serotonin from intracellular space once it was released, Dr. Moses reported.However, serotonin release from endocrine cells was not significantly different in cases and controls, he said.The bottom line, according to Dr. Moses, is that "patients with IBS have a deceased ability to remove serotonin once it is released. This tells us for the first time that there is a definitive change in the bowels of patients with IBS.""It's not a matter of too much or too little serotonin, but how the serotonin molecules interact with the receptor," said Kevin W. Olden, MD, associate professor of medicine in the Division of Gastroenterology at the Mayo Clinic in Scottsdale, Arizona."We'll see an explosion of drugs in this area," he said. "Interventions that target serotonin receptors in the brain have revolutionized the treatment of depression and this goes way beyond that."Lawrence Brandt, MD, a gastroenterologist at Montefiore Hospital in the Bronx, New York, agreed and noted two such drugs are already on the market. "The more serotonin you have, the more peristalsis," he said. That's why drugs that activate serotonin receptors, such as tegaserod, help relieve constipation, he said. "Patients with too much serotonin, on the other hand, have diarrhea," Dr. Brandt said. "If we could interrupt that pathway and block it with a serotonin analog, we could help." One such drug, alosetron, is currently available, he said.The selective serotonin reuptake inhibitors that are used to treat depression do not help patients with gastrointestinal disorders because they target a different subtype of serotonin receptors, Dr. Olden said. The study was funded by Novartis Pharmaceuticals, the manufacturer of tegaserod, and one author has received financial support from Novartis. ACG 68th Annual Scientific Meeting: Abstract 20. Presented Oct. 13, 2003."It is very important to realize there are lots of neurotransmitters in the gut and they interact, so this is very complex in itself, but they do not think those receptors are function right. Even though that study was funded by novartis a ton of research has been done on serotonin and IBS and a lot more being domne.But importantly in this they have found the receptors that help to : regulating motility, visceral sensitivity, and intestinal secretion.So its not a matter of how much is in the body, but how its regulating or dysregulating in IBS within certain cells in the gut.I need to emphasize one more time, this is only part of the picture in IBS, but they have known this for quite a few years now.If you want more info read this also.IBS: Improving Diagnosis, Serotonin Signaling, and Implications for Treatment CMEAuthors: Lucinda Harris, MD; Lin Chang, MD
http://www.medscape.com/viewprogram/2750