Positron Emission Tomography Study of the Effects of Tryptophan Depletion on Brain Serotonin<sub>2</sub>Receptors in Subjects Recently Remitted From Major Depression
Bibliographic record
Abstract
CONTEXT: Decreased brain serotonin (5-hydroxytryptamine) levels are considered to mediate depressive relapse induced by the tryptophan depletion paradigm. However, in patients who recently achieved remission from a major depressive episode with antidepressant treatment, only about half become depressed following tryptophan depletion. We hypothesized that downregulation of brain serotonin(2) receptors might be a compensatory mechanism that prevents some patients from becoming depressed with tryptophan depletion. OBJECTIVE: To assess, with use of positron emission tomography, whether brain serotonin(2) receptor downregulation occurs in patients with recently remitted depression who do not have depressive relapse, but not in those who become depressed, following tryptophan depletion. DESIGN: Each patient underwent 2 fluorine 18-labeled- setoperone positron emission tomography scans, one following a tryptophan depletion session and another following a control session. The order of scanning was counterbalanced. SETTING: Academic university hospital with imaging facilities. PARTICIPANTS: Seventeen patients in recent remission from a DSM-IV major depressive episode following treatment with selective serotonin reuptake inhibitors. MAIN OUTCOME MEASURES: Changes in brain serotonin(2) receptor binding. RESULTS: Of the 17 patients, 8 (47%) became depressed during the tryptophan depletion session, and none developed depression during the control session. The depletion session was associated with a significant reduction in brain serotonin(2) receptor binding compared with the control session for all participants. A subgroup analysis revealed that the reduction in serotonin(2) receptor binding was significant only for the nondepressed group. CONCLUSION: Reduction in brain serotonin(2) receptors might be a potential compensatory mechanism to prevent tryptophan depletion-induced depressive relapse.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".