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Gender effects and central opioid analgesia.
Karen L Kepler1, Kelly M Standifer, Dennis Paul
1Department of Psychology and Neuropsychology, Queens College, CUNY, Flushing, NYU.S.A. George Cotzias Laboratory of Neuro-Oncology, Memorial Sloan-Kettering Cancer Center, New York, NYU.S.A. Departments of Neurology, Pharmacology and Neuroscience, Cornell University Medical College, New York, NYU.S.A.
Pain
|April 1, 1991
Summary
Male rats exhibit greater central morphine analgesia than females, particularly with mu-opioid receptor agonists. This gender difference in pain relief was observed on the tail-flick test but not the jump test.
Area of Science:
- Neuroscience
- Pharmacology
- Pain Research
Background:
- Central morphine analgesia shows significant gender differences, being greater in males than females.
- Mu (μ) and delta (δ) opioid receptor subtypes are crucial for supraspinal analgesia, but their role in gender-specific pain perception requires further investigation.
Purpose of the Study:
- To investigate the influence of gender and gonadectomy on analgesia mediated by central mu- and delta-opioid receptor agonists.
- To determine if gender affects opioid receptor binding in specific brain regions.
Main Methods:
- Central administration of a mu-selective agonist ([D-Ala2, Me-Phe4, Gly(ol)5] enkephalin - DAMGO) and a delta-selective agonist ([D-Ser2, Leu5] enkephalin-Thr6 - DSLET) in male and female rats.
- Assessment of analgesia using tail-flick and jump tests.
- Evaluation of mu1, mu2, and delta opioid receptor binding in hypothalamic and cortical tissues.
Main Results:
- Male rats showed significantly greater analgesia than females on the tail-flick test after DAMGO administration, but not DSLET.
- No significant gender differences in analgesia were observed on the jump test for either agonist.
- Gonadectomy did not consistently alter analgesia for either agonist.
- No gender differences were found in mu1, mu2, or delta opioid receptor binding in the hypothalamus or cortex.
Conclusions:
- Gender influences supraspinal analgesia, particularly mu-opioid receptor-mediated pain relief, as demonstrated by the tail-flick test.
- The observed gender differences in analgesia are not explained by alterations in central mu or delta opioid receptor binding in the hypothalamus or cortex.