Effects of rapid tryptophan depletion on brain 5-HT2receptors: a PET study

Abstract

BackgroundThe mechanism by which rapid tryptophan depletion (RTD) paradigm induces depressive relapse in recently remitted patients with depression is unknown.AimsTo determine the effects of RTD on brain 5-HT2receptors using positron emission tomography (PET) and18F-labelled setoperone.MethodTen healthy women underwent two PET scans. Each scan was done 5 h after the ingestion of either a balanced or a tryptophan-deficient amino acid mixture, and the two test sessions were separated by at least 5 days.ResultsThe RTD decreased plasma free tryptophan levels significantly but it had no significant effects on mood. Subjects showed a significant decrease in brain 5-HT2receptor binding in various cortical regions following the RTD session.ConclusionsWhen taken with the evidence that antidepressant treatment is associated with a decrease in brain 5-HT2receptors, these findings suggest that a decrease in 5-HT2binding following RTD might be an adaptive response that provides protection against depressive symptoms.