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Canadian Journal of Gastroenterology
Volume 17, Issue 3, Pages 191-196
Original Article

Sex Differences of Brain Serotonin Synthesis in Patients with Irritable Bowel Syndrome Using α-[11C]methyl-L-tryptophan, Positron Emission Tomography and Statistical Parametric Mapping

Akio Nakai,1,4 Yoshikata Kumakura,1 Michel Boivin,2 Pedro Rosa,1 Mirko Diksic,1 Doreen D’Souza,3 and Kathryn Kersey3

1Montreal Neurological Institute, McGill University, Montreal, Canada
2Centre Hospitalier de l’Universite de Montreal, Montreal, Quebec, Canada
3Glaxo Wellcome Inc, Mississauga, Ontario, Canada
4Permanent address, Department of Pediatrics, Fukui Medical University School of Medicine, Fukui, Japan

Received 9 September 2002; Revised 19 December 2002

Copyright © 2003 Hindawi Publishing Corporation. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


BACKGROUND: Irritable bowel syndrome (IBS) is the most common functional bowel disorder and has a strong predominance in women. Recent data suggest that the brain may play an important role in the pathophysiology of IBS in the brain-gut axis. It is strongly suspected that serotonin (5-HT), a neurotransmitter found in the brain and gut, may be related to the pathophysiology of IBS. It is reported that a 5-HT3 antagonist is effective only in female patients with diarrhea-predominant IBS.

OBJECTIVE: In the present study, 5-HT synthesis was measured using positron emission tomography, with α-[11C]methyl-l-tryptophan as the tracer, in patients with IBS. The aim of the present study was to compare 5-HT synthesis in the IBS patients with that in the controls, and to compare 5-HT synthesis between male and female IBS patients.

METHODS: Six male and six female nonconstipated IBS patients were scanned. Age-matched healthy volunteers were scanned as controls. Eighty minute dynamic scans were performed. Functional 5-HT synthesis images were analyzed using statistical parametric mapping.

RESULTS: 5-HT synthesis was greater only in the female IBS patients in the right medial temporal gyrus (multimodal sensory association cortex) compared with the female controls (P<0.001).

CONCLUSIONS: The greater brain 5-HT synthesis in the female IBS patients than in the controls may be related to the pathological visceral pain processing of the IBS patients, a larger female predominance of the disorder, and the sex difference of the efficacy of the 5-HT3 antagonist in treatment.