Hyperresponsiveness to the Inhibitory Action of Dopamine Agonists on Luteinizing Hormone Secretion in the Monosodium-L-Glutamate-Treated, Orchidectomized Rat
Bibliographic record
Abstract
The tuberoinfundibular (A12) dopaminergic pathway, which originates in the arcuate and periventricular nuclei, is thought to play an inhibitory role in the regulation of episodic luteinizing hormone (LH) secretion. Neonatal treatment of rats with the neurotoxin monosodium-L-glutamate (MSG) causes extensive damage to the arcuate nuclei and up to 60% depletion of dopamine (DA) in the mediobasal hypothalamus. We hypothesized that such DA depletion should result in a hyperresponsiveness to subsequent administration of a DA agonist. To test this hypothesis, male rats were treated neonatally with MSG. Control rats received injections of equiosmotic saline. As adults the rats were orchidectomized and fitted with indwelling venous catheters. Blood samples were taken from these unanesthetized, unrestrained rats at 5-min intervals for a 1-hour period, at which time the animals received an intraperitoneal injection of one of the following drugs: apomorphine (0.8 mg/kg, a DA receptor agonist), bromocriptine (8.0 mg/kg, a DA receptor agonist), 0.9% saline (vehicle for apomorphine) or 95% ethanol (vehicle for bromocriptine). Blood sampling was continued for a further 2-2.5 h. Plasma LH was measured by RIA. Both apomorphine and bromocriptine produced striking inhibition of circulating LH levels in MSG-treated rats. Neither of the control treatments altered pulsatile LH secretion patterns. Administration of exogenous gonadotropin-releasing hormone produced LH peaks in all animals so treated, including those whose endogenous LH secretion had been inhibited by the DA agonists. These findings suggest that the depletion of DA induced by neonatal MSG treatment results in a supersensitivity to DA agonists.(ABSTRACT TRUNCATED AT 250 WORDS)
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| 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) | 0.000 | 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 teacher head, 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".