Testosterone and dihydrotestosterone, but not estradiol, enhance survival of new hippocampal neurons in adult male rats
Bibliographic record
Abstract
Past research suggested that androgens may play a role in the regulation of adult neurogenesis within the dentate gyrus. We tested this hypothesis by manipulating androgen levels in male rats. Castrated or sham castrated male rats were injected with 5-Bromo-2'deoxyuridine (BrdU). BrdU-labeled cells in the dentate gryus were visualized and phenotyped (neural or glial) using immunohistochemistry. Castrated males showed a significant decrease in 30-day cell survival within the dentate gyrus but there was no significant change in cell proliferation relative to control males, indicating that androgens positively affect cell survival, but not cell proliferation. To examine the role of testosterone on hippocampal cell survival, males were injected with testosterone s.c. for 30 days starting the day after BrdU injection. Higher doses (0.5 and 1.0 mg/kg) but not a lower dose (0.25 mg/kg) of testosterone resulted in a significant increase in neurogenesis relative to controls. We next tested the role of testosterone's two major metabolites, dihydrotestosterone (DHT), and estradiol, upon neurogenesis. Thirty days of injections of DHT (0.25 and 0.50 mg/kg) but not estradiol (0.010 and 0.020 mg/kg) resulted in a significant increase in hippocampal neurogenesis. These results suggest that testosterone enhances hippocampal neurogenesis via increased cell survival in the dentate gyrus through an androgen-dependent mechanism.
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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 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 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) | 0.002 | 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".