Authors: Dunlop SP, Coleman NS, Blackshaw E, Perkins AC, Singh G, Marsden CA, Spiller RC.

Institution: Division of Gastroenterology, University Hospital, Nottingham NG7 2UH, UK.

Background: 5-hydroxytryptamine-3 (5-HT 3 ) receptor antagonists improve symptoms in patients with diarrhea-predominant irritable bowel syndrome (D-IBS), 5-HT 4 agonists help those with constipation-predominant IBS (C-IBS). These data suggest excess or deficiency in 5-HT in D-IBS or C-IBS, respectively. Mucosal 5-HT-containing enterochromaffin cells (EC) are increased in postinfectious IBS (PI-IBS). Our aim was to define the postprandial release of 5-HT in PI-IBS and C-IBS patients and to relate this to mucosal 5-HT turnover.

Results: Colonic transit was prolonged in C-IBS patients (mean +/- SEM) (49.4 +/- 3.8 h) compared with PI-IBS (26.7 +/- 4.5) and control patients (34.1 +/- 4.5) ( P < .02). Release of 5-HT assessed by area under the curve (AUC) of platelet-poor plasma 5-HT from 0 to 180 minutes postprandially was significantly lower in C-IBS patients (2593 +/- 309 mmol/L . min) compared with P-IBS (5623 +/- 721) and control patients (4822 +/- 598) ( P < .001). PI-IBS patients showed significantly higher peak postprandial plasma 5-HT values…

Conclusions: C-IBS patients show impaired postprandial 5-HT release whereas PI-IBS patients have higher peak levels, abnormalities that may be related to their different symptoms.

Study link: http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=15822040&query_hl=9&itool=pubmed_docsum

• Irritable Bowel Syndrome: Update on Pathogenesis and Management
• Patients With Constipation-Predominant Irritable Bowel Syndrome (IBS) May Have Elevated Serotonin Concentrations in Colonic Mucosa as Compared With Diarrhea-Predominant Patients and Subjects with Normal Bowel Habits
• Abnormalities of 5-Hydroxytryptamine Metabolism in Irritable Bowel Syndrome