Effects of rapid tryptophan depletion on brain 5-HT2 receptors: A PET study

Abstract

Background: The mechanism by which rapid tryptophan depletion (RTD) paradigm induces depressive relapse in recently remitted patients with depression is unknown. Aims: To determine the effects of RTD on brain 5-HT2 receptors using positron emission tomography (PET) and 18F-labelled setoperone. Method: Ten healthy women under went two PETscans. 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. Results: The RTD decreased plasma free tryptophan levels significantly but it had no significant effects on mood. Subjects showed a significant decrease in brain 5-HT2 receptor binding in various cortical regions following the RTD session. Conclusions: When taken with the evidence that antidepressant treatment is associated with a decrease in brain 5-HT2 receptors, these findings suggest that a decrease in 5-HT2 binding following RTD might be an adaptive response that provides protection against depressive symptoms. Declaration of interest: None.