| 15476688 |
Praschak-Rieder N, Hussey D, Wilson AA, Carella A, Lee M, Dunn E, Willeit M, Bagby RM, Houle S, Meyer JH: Tryptophan depletion and serotonin loss in selective serotonin reuptake inhibitor-treated depression: an [(18) F] MPPF positron emission tomography study. Biol Psychiatry. 2004 Oct 15;56(8):587-91.
BACKGROUND: Recurrence of depressive symptoms after tryptophan depletion (TD) in selective serotonin reuptake inhibitor (SSRI)-treated depression is an important, unexplained phenomenon. With [(18) F] MPPF positron emission tomography (PET), serotonin (5-hydroxytryptamine, 5-HT) 1A receptor binding potential (5-HT (1A) BP) was measured after TD in various brain regions in citalopram-treated depression. This 5-HT (1A) BP measurement is sensitive to changes in extracellular 5-HT in animal models. METHODS: Eight remitted patients with major depressive disorder received [(18) F] MPPF PET scans twice: once after TD and once after sham depletion. Behavioral measures were evaluated with the Hamilton Depression Rating Scale and visual analog scales. RESULTS: No effect on regional 5-HT (1A) BP was observed after TD, despite an 86% decrease in total plasma tryptophan and transient depressive relapse in six of eight patients. CONCLUSIONS: Large-magnitude changes in extracellular 5-HT are not crucial for the mood effects observed in SSRI-treated subjects after TD. Therefore, greater consideration must be given to other mechanisms that involve vulnerability to small perturbations in extracellular 5-HT, such as impairment of signal transduction. |
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