Comparison of the Duration of Action of Nalmefene and Naloxone on the Hypothalamic-Pituitary Axis of the Rhesus Monkey
Bibliographic record
Abstract
The duration of action of nalmefene, a relatively new opiate antagonist, on the hypothalamic-pituitary axis of the rhesus monkey was compared to that exhibited by naloxone. Ovariectomized monkeys (n = 5) were pretreated with 10 mg nalmefene, 10 mg naloxone or an equivalent volume of saline 12, 24, or 48 h prior to the administration of 10 mg morphine. Blood samples were collected by venipuncture 0, 1, 2, 3 and 4 h after injection of morphine and were assayed for luteinizing hormone (LH) and prolactin (PRL). Duration of action of these two opiate antagonists was estimated from their ability to block morphine inhibition and stimulation of LH and PRL release respectively. Morphine reduced serum LH concentration by 60% and increased PRL levels approximately 4-fold in saline-pretreated animals. Administration of nalmefene either 12 or 24 h, but not 48 h prior to morphine, significantly antagonized the effects of this opiate on LH and PRL release. In contrast, naloxone at all pretreatment intervals failed to block morphine's effect. We conclude that a single 10 mg bolus injection of nalmefene exerts significant activity at the opiate receptors that mediate the effects of morphine on LH and PRL release for at least 24 h after administration, whereas the same dose of naloxone has a duration of action less than 12 h. Based on this finding it is likely that the effects of endogenous opioid peptides in the rhesus monkey can be chronically antagonized by the daily administration of nalmefene.
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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 | 0.000 | 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".