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Spinal adenosine modulates descending antinociceptive pathways stimulated by morphine
The Journal of Pharmacology and Experimental Therapeutics
|October 1, 1986
Summary
This study shows that spinal adenosine plays a role in opioid-induced pain relief by interacting with opioid receptors. Blocking adenosine receptors reduces the pain-killing effects of morphine.
Area of Science:
- Neuroscience
- Pharmacology
- Pain Research
Background:
- Opioid and adenosine interactions influence analgesia in the brain.
- Previous research suggests potential interactions at spinal sites.
Purpose of the Study:
- To investigate opioid-adenosine interactions within the spinal cord.
- To determine if adenosine modulates opioid-stimulated descending antinociceptive pathways.
Main Methods:
- Administered methylxanthines (adenosine receptor antagonists) intrathecally (i.t.).
- Tested theophylline's effect on morphine- and 2-chloroadenosine-induced analgesia.
- Used tail-flick and hot-plate assays to measure antinociception.
- Administered naloxone (i.t.) to assess opioid receptor involvement.
Main Results:
- Intrathecal theophylline dose-dependently antagonized analgesia from both intrathecal and intracerebroventricular (i.c.v.) morphine.
- Theophylline also antagonized analgesia induced by an adenosine agonist (2-chloroadenosine).
- Naloxone blocked morphine analgesia but not that induced by 2-chloroadenosine, supporting spinal adenosine release by morphine.
Conclusions:
- Endogenous adenosine in the spinal cord is implicated in opioid-mediated analgesia.
- Adenosine likely participates in opioid-stimulated descending antinociceptive pathways.