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Irritable bowel syndome (IBS) is a common disorder 1 2 but despite this the pathophysiology is far from understood. Visceral hypersensitivity, expressed as lowered perception thresholds to balloon distension in different parts of the gastrointestinal tract 3-5 and to physiological intestinal motility, 6 is a feature in many patients. Furthermore, they also demonstrate an altered viscerosomatic referral pattern as another indicator of disturbed processing of viscerosensory information. 7
Eating a meal stimulates colonic myoelectrical and motor activity. 8 9 This gastrocolonic response consists of a gastric phase mediated by mechanoreceptors and an intestinal phase mainly due to stimulation of chemoreceptors where the fat component of the food is the main stimulus. 10 11 Postprandial symptoms are common in IBS 12 and several studies show a prolonged and exaggerated gastrocolonic response in terms of myoelectrical and motor activity 13-15 but colonic tone is not altered. 16 17 Recent investigations have shown increased jejunal sensitivity after feeding in both IBS patients and healthy controls 18 and increased rectal sensitivity after a meal in healthy individuals. 19 Fat is also the main stimulus for this sensory component of the gastrocolonic response. 20
The role of gastrointestinal neuropeptides in the generation of symptoms in IBS patients is unclear but differences compared with the normal population have been reported in blood levels of 5-hydroxytryptamine (5-HT), 21 motilin, cholecystokinin (CCK), 22 gastrin, and pancreatic polypeptide (PP). 23 Furthermore, CCK and a high fat meal can unmask dysmotility and produce symptoms in IBS patients. 24
Most of the previous studies on viscerosensory abnormalities in IBS patients were done in the fasting state and colonic perception thresholds following nutrients have not been investigated previously. As postprandial symptoms are frequent, the aim of the present study was to investigate the sensory component of the gastrocolonic response to a nutrient and to relate the findings to changes in gastrointestinal peptides.
Methods
SUBJECTS
We studied 16 patients with IBS (14 women, two men; mean age 39 years (range 22-56))-eight with diarrhoea predominant (IBS-D) and eight with constipation predominant (IBS-C) IBS-referred to our clinic from primary care physicians. All fulfilled the Rome criteria for IBS 25 and organic gastrointestinal disorders were excluded by routine laboratory tests and colonoscopy with biopsies. The control group consisted of 13...