title: Altered 5-hydroxytryptamine signaling in patients with constipation- and diarrhea-predominant irritable bowel syndrome.
abstract: OBJECTIVE
  Evidence suggests that postprandial platelet-depleted plasma 5-hydroxytryptamine (5-HT) concentrations may be abnormal in irritable bowel syndrome (IBS). However, interpretation of the data has been hampered by the variable methodology and rather small numbers used in previous studies. Therefore, the aim of this study was to measure concentrations of platelet-depleted plasma 5-HT and its metabolite 5-HIAA under fasting and fed conditions in a large group of patients with diarrhea-predominant (d-) and constipation-predominant (c-) IBS, compared with controls. The ratio of plasma 5-HIAA:5-HT and platelet stores was also assessed.
  
  
  METHODS
  Twenty-nine c-IBS patients (aged, 19-53 years), 55 d-IBS patients (aged, 19-52 years), and 35 healthy volunteers (aged, 18-46 years) had platelet-depleted plasma 5-HT/5-HIAA concentrations measured using reverse-phase, high-performance liquid chromatography with fluorimetric detection before and after a standard meal.
  
  
  RESULTS
  d-IBS patients had raised platelet-depleted plasma 5-HT concentrations under fasting and fed conditions (P < .05). However, the postprandial relative to fasting concentration was similar to controls. In contrast, c-IBS patients failed to show an increase in platelet-depleted plasma 5-HT concentration with meal ingestion compared with controls (P < .01). c-IBS was associated with decreased 5-HIAA (P < .01) but normal 5-HIAA:5-HT ratio and d-IBS with normal 5-HIAA concentrations but reduced 5-HIAA:5-HT ratio (P < .005). C-IBS but not d-IBS patients had increased platelet 5-HT.
  
  
  CONCLUSIONS
  These results support the concept that d-IBS is characterized by reduced 5-HT reuptake, whereas impaired release may be a feature of c-IBS. These results also provide a rational basis for current pharmacologic approaches involving modulation of different 5-HT receptors in c- and d-IBS.
authors.affiliation: Neurogastroenterology Unit, Academic Division of Medicine and Surgery, University Hospital of South Manchester, Manchester, United Kingdom.
authors.forename: Wendy
authors.initials: W
authors.lastname: Atkinson
authors.forename: Stephen
authors.initials: S
authors.lastname: Lockhart
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Whorwell
authors.forename: Brian
authors.initials: B
authors.lastname: Keevil
authors.forename: Lesley A
authors.initials: LA
authors.lastname: Houghton
mesh_terms: D000328:Adult; D016022:Case-Control Studies; D002851:Chromatography, High Pressure Liquid; D003248:Constipation / Q000209:etiology / Q000503:physiopathology*; D003967:Diarrhea / Q000209:etiology / Q000503:physiopathology*; D005215:Fasting; D005260:Female; D006801:Humans; D006897:Hydroxyindoleacetic Acid / Q000097:blood / Q000378:metabolism; D043183:Irritable Bowel Syndrome / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D019518:Postprandial Period; D012701:Serotonin / Q000097:blood / Q000378:metabolism*; D015398:Signal Transduction
chemical_list: D012701:Serotonin; D006897:Hydroxyindoleacetic Acid