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Age-dependent antinociception and behavioral inhibition by morphine
Alok Kumar Paul1, Nuri Gueven1, Nikolas Dietis1
1Division of Pharmacy, School of Medicine, University of Tasmania, Australia.
Pharmacology, Biochemistry, and Behavior
|March 18, 2018
Summary
Older rats exhibit prolonged morphine antinociception and increased behavioral inhibition compared to younger rats. This suggests higher morphine accumulation in the brains of older animals, impacting pain management and drug effects in aging populations.
Area of Science:
- Pharmacology
- Neuroscience
- Gerontology
Background:
- Current clinical practice doses morphine in older patients based on weight, lacking clear evidence for age-related antinociception and behavioral effects.
- Limited literature exists on the relationship between morphine, antinociception, and behavior in aging populations.
Purpose of the Study:
- To compare the antinociceptive and behavioral effects of morphine in young (8-week-old) versus aged (24-week-old) rats.
- To investigate morphine distribution in various tissues, particularly the brain, in relation to age.
Main Methods:
- Subcutaneous administration of morphine based on body weight in rats of different ages (8 and 24 weeks).
- Assessment of nociceptive response and behavioral analysis using an advanced multi-conditioning system.
- Quantification of residual morphine in major tissues at 240 minutes post-injection.
Main Results:
- Older rats demonstrated prolonged morphine-induced antinociception compared to younger rats.
- Morphine significantly stimulated locomotor and rearing behavior, with higher intensity in younger rats at 180 minutes.
- Significantly higher residual morphine concentrations were found in the brains of older rats when standardized by tissue weight, but not by protein content.
Conclusions:
- Morphine exhibits enhanced antinociception and increased behavioral inhibition in older rats compared to younger ones.
- Higher brain accumulation of morphine in older rats may explain the observed prolonged effects and altered behavioral responses.
- Findings suggest age-related differences in morphine pharmacokinetics and pharmacodynamics warrant consideration in clinical practice.
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