American journal of physiology. Gastrointestinal and liver physiology vol:300 issue:2 pages:G228-35
Peripheral serotonin (5-HT) is involved in the regulation of gastrointestinal motility and sensation, while centrally it plays a role in mood regulation. A dysfunctional serotonergic system may provide a plausible link between functional dyspepsia symptoms and its high psychosocial comorbidity such as anxiety and depression.
To evaluate the effect of decreased 5-HT synthesis by acute tryptophan depletion (ATD) on: gastric sensorimotor function & nutrient tolerance, anxiety scores and gastrointestinal mucosal 5-HT concentrations in healthy volunteers.
All subjects were studied under a control condition and during ATD. Gastric sensorimotor function and nutrient tolerance were assessed using a barostat (n=16, 28.8±1.4 yrs) and a satiety drinking test (n=13, 27.3±1.4 yrs). Anxiety during the barostat was evaluated using STAI state questionnaire. 5-HT concentrations were measured in fundic and duodenal mucosal biopsies by means of ELISA and immunohistochemistry.
ATD significantly decreased plasma tryptophan levels compared to control in every experiment. ATD did not affect gastric sensitivity and compliance, but decreased the sensation of nausea during balloon distension (AUC 17.4±4.3 vs. 11.4±3.4 mm*mmHg, p=0.030). ATD enhanced the postprandial volume increase (ANOVA, p<0.05), but this was not accompanied by augmented nutrient tolerance (848±110 vs. 837±99 ml, NS). ATD had no effect on STAI state anxiety scores. No evidence was found for an effect on the number of enterochromaffin cells but ATD reduced 5-HT levels in the duodenal mucosa.
ATD alters gastric postprandial motor function and distention-induced nausea. These findings confirm involvement of 5-HT in the control of gastric accommodation and sensitivity.