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Stress reduces morphine's antinociceptive potency: dependence upon spinal cholecystokinin processes
1Department of Pharmacology/Toxicology, P.O. Box 9223, Robert C. Byrd Health Sciences Center of West Virginia University, Morgantown, WV 26506-9223, USA.
Brain Research
|April 10, 1999
Summary
Stress significantly reduces the pain-relieving effects of morphine, a common opioid. This effect is reversed by blocking cholecystokinin (CCK) receptors, suggesting CCK
Area of Science:
- Neuroscience
- Pharmacology
- Pain Research
Background:
- Stress impacts opioid efficacy, as previously shown with beta-endorphin.
- Repetitive heat stress in rats induced analgesia but reduced beta-endorphin potency in the periaqueductal gray (PAG).
Purpose of the Study:
- To investigate the effect of the same stressor on morphine's antinociceptive potency.
- To determine the role of cholecystokinin (CCK) in stress-induced alterations of morphine's effects.
Main Methods:
- Rats were exposed to repetitive noxious heat stress.
- Morphine was administered intraperitoneally (i.p.) and intracerebrally.
- The CCK receptor antagonist L-365,260 was administered intrathecally.
Main Results:
- Stress significantly reduced morphine's antinociceptive potency, irrespective of administration route.
- Intrathecal administration of L-365,260 reversed the stress-induced reduction in morphine potency.
- Findings suggest spinal CCK-dependent anti-analgesic processes are involved in stress effects.
Conclusions:
- Stress alters the effectiveness of morphine, a key consideration for clinical pain management.
- CCK receptor antagonists may enhance the reliability and effectiveness of opioid pain therapy.