Original Contribution
The American Journal of Gastroenterology (2006) 101, 2582–2587; doi:10.1111/j.1572-0241.2006.00811.x
Acute Tryptophan Depletion Alters Gastrointestinal and Anxiety Symptoms in Irritable Bowel Syndrome
Jonathan Shufflebotham MRCP1, Sean Hood MSc, FRANZCP2, Julie Hendry MRCPsych3, Dana A Hince PhD4, Kelly Morris MBBChir4, David Nutt DM, FRCP, FRCPsych, FMedSci4, Chris Probert MD, FRCP1 and John Potokar MD, MRCPsych4
- 1Clinical Science at South Bristol, University of Bristol, Bristol, United Kingdom
- 2School of Psychiatry & Clinical Neurosciences, University of Western Australia, Perth, Australia
- 3Bristol Royal Infirmary, Bristol, United Kingdom
- 4Psychopharmacology Unit, University of Bristol, Bristol, United Kingdom
Correspondence: John Potokar, MD, MRCPsych, Psychopharmacology Unit, University of Bristol, Bristol, UK.
Received 21 December 2005; Accepted 25 May 2006.
Abstract
OBJECTIVES:
To assess the effect of acute changes in serotonin (5-HT) synthesis using the acute tryptophan depletion (ATD) paradigm on gastrointestinal (GI) and mood symptoms in irritable bowel syndrome (IBS).
METHODS:
In a randomized double-blind crossover study, 29 subjects (18 patients with ROME II defined IBS and 11 age-matched controls) were studied under ATD and acute tryptophan increase (ATI) conditions. GI symptoms, mood and anxiety ratings, as well as plasma tryptophan concentrations were measured.
RESULTS:
Total (and free) plasma tryptophan concentrations decreased on the ATD day in patients (73% [82%]) and controls (73% [80%]), and increased on the ATI day in patients (59% [143%]) and controls (61% [381%]). Compared with the ATD day, IBS patients reported more GI symptoms on the ATI day at +210 (p < 0.001) and at +270 (p < 0.05) min post drink. IBS patients also reported less anxiety on the ATI day compared with the ATD day at +270 min (p < 0.001). ATD and ATI did not affect these ratings in control participants. IBS patients had a lower mood compared with controls (p < 0.05), but this did not differ between the ATI and ATD days in either group.
CONCLUSIONS:
IBS patients' GI and anxiety responses to changes in tryptophan load differ from controls. This suggests a difference in serotonergic functioning between these two groups and provides evidence to support the hypothesis that 5-HT dysfunction is involved in IBS.
