The mechanism by which rapid tryptophan depletion (RTD) paradigm induces depressive relapse in recently remitted patients with depression is unknown.
To determine the effects of RTD on brain 5-HT(2) receptors using positron emission tomography (PET) and (18)F-labelled setoperone.
Ten healthy women under went 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.
The RTD decreased plasma free tryptophan levels significantly but it had no significant effects on mood. Subjects showed a significant decrease in brain 5-HT(2) receptor binding in various cortical regions following the RTD session.
When taken with the evidence that antidepressant treatment is associated with a decrease in brain 5-HT(2) receptors, these findings suggest that a decrease in 5-HT(2) binding following RTD might be an adaptive response that provides protection against depressive symptoms.
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