Sex Differences in Pain and Hypothalamic-Pituitary-Adrenocortical Responses to Opioid Blockade
Bibliographic record
Abstract
Objective: Sex differences in pain sensitivity and stress reactivity have been well documented. Little is known about the role of the endogenous opioid system in these differences. This study was conducted to compare adrenocortical, pain sensitivity, and blood pressure responses to opioid blockade using naltrexone in men and women. Methods: Twenty-six participants completed 2 sessions during which placebo or 50 mg of naltrexone was administered, using a double-blind, counterbalanced design. Thermal pain threshold and heat tolerance were assessed. Participants also rated pain during a 90-second cold pressor test (CPT) and completed the McGill Pain Questionnaire (MPQ) after each pain challenge. Blood and saliva samples and cardiovascular and mood measures were obtained throughout the sessions. Results: Plasma cortisol, adrenocorticotropin, beta endorphin, prolactin, and salivary cortisol levels increased similarly in men and women after naltrexone administration compared with placebo. Women reported more pain during both pain procedures and had lower thermal pain tolerance. In response to naltrexone, women exhibited reduced blood pressure responses and reduced MPQ pain ratings after CPT. No effects of naltrexone on these measures were found in men. Conclusions: Although men and women exhibited similar hormonal responses to opioid receptor blockade, women reported less pain and showed smaller blood pressure responses during CPT. Results suggest differential effects of the endogenous opioid system on pain perception and blood pressure in men and women. Key words: pain, stress, gender differences, cortisol, adrenocortico-tropin, naltrexone. CPT cold pressor test; HPA hypothalamic–pituitary–adreno-cortical; HR heart rate; MPQMcGill Pain Questionnaire; SV stroke volume.
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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 | 0.001 |
| 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) | 0.004 | 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".