In vitro<b> </b>Autoradiographic Analysis of Regional Changes in Estrogen Receptor Alpha in the Brains of Cycling Female Rats
Bibliographic record
Abstract
BACKGROUND/AIMS: The contributions of the three principal ovarian steroid hormones (estradiol, progesterone and testosterone) to the regulation of estrogen receptor alpha (ERα) levels in the rat brain were examined during the estrous cycle. METHODS: Receptor concentrations were measured using an in vitro autoradiographic technique designed to separately quantify free, unoccupied receptors and receptors 'occupied' by (bound to) endogenous hormone. RESULTS: ERα occupation increased at proestrus and declined at estrus, reflecting changes in circulating estradiol and testosterone levels. Total ERα content followed a pattern that was the inverse of the occupation data, falling over the night of proestrus. Between 2.00 and 10.00 a.m. on the day of estrus, total ERα concentrations recovered in all brain regions except the ventromedial nucleus (VMN), in which ERα binding remained depressed at estrus. Administration of the progesterone antagonist mifepristone on the afternoon of proestrus resulted in recovery of ERα levels in the VMN by the morning of estrus, consistent with the hypothesis that the preovulatory progesterone surge selectively inhibits VMN ERα expression. Residual ERα occupation observed at estrus, when estradiol is not detectable in the serum, likely reflects intracranial aromatization of circulating androgens, since the pattern of receptor occupation observed at this stage of the cycle could be reproduced in ovariectomized rats by replacement with testosterone. CONCLUSION: These findings indicate that ERα binding in the brain fluctuates during the rat estrous cycle in a region-specific manner and suggest that local aromatization of testosterone may contribute significantly to ERα occupation when circulating estradiol levels are low.
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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) | 0.001 | 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 | 0.001 |
| Insufficient payload (model declined to judge) | 0.003 | 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".