Developmental Time Course of Estradiol, Testosterone, and Dihydrotestosterone Levels in Discrete Regions of Male and Female Rat Brain
Bibliographic record
Abstract
The prevailing view of sexual differentiation of mammalian brain is that androgen synthesized in the fetal and neonatal testis and aromatized centrally during a perinatal sensitive period is the sole source of brain estradiol and the primary determinant of sex differences. Subregions of the diencephalon are among the most sexually dimorphic in the brain, and there are well-established sex differences in the amount of testosterone and estradiol measured in the hypothalamus and preoptic area during the perinatal period. We previously reported unexpectedly high estradiol in the hippocampus and cortex of both male and female newborn rat. This prompted a thorough investigation of the developmental profile of steroids in the rat brain using RIA to quantify the level of estradiol, testosterone, and dihydrotestosterone in discrete subregions of the brain from embryonic d 19 to adulthood. Plasma estradiol levels from individual animals were assessed when sufficient sample was available. A significant sex difference in hypothalamic testosterone prior to birth was consistent with previous findings. Postnatally, there was a distinct pattern of changing steroid concentrations in each brain region, and these were unrelated to circulating steroid. Removal of the gonads and adrenals at birth did not significantly reduce steroids in any brain region assayed 3 d later. Aromatase activity was detectable in all brain areas at birth, and the difference in activity level paralleled the observed regional differences in estradiol content. Based on these findings, we propose that steroidogenesis in the brain, independent of peripherally derived precursors, may play a critical role in mammalian brain development of both sexes, beyond the establishment of sex differences.
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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 | 0.001 |
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".