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Gastric cytoprotective effect of morphine is probably not mediated by mu-receptors

S A Bhounsule1, R S D'Souza, V G Dhume

  • 1Department of Pharmacology, Goa Medical College, India.

Archives Internationales De Pharmacodynamie Et De Therapie
|July 1, 1994
PubMed

Insights

Morphine protects against ethanol-induced gastric lesions, but this effect is not mediated by mu-opioid receptors. Other opioids targeting these receptors failed to show protection, suggesting a different mechanism for opioid-induced gastric cytoprotection.

Area of Science:

  • Pharmacology
  • Gastroenterology
  • Toxicology

Background:

  • Opioids are known to affect gastrointestinal functions.
  • Morphine demonstrates a protective effect against ethanol-induced gastric lesions.
  • This protective effect is antagonized by naloxone, indicating involvement of opioid receptors.

Purpose of the Study:

  • To investigate the role of mu-opioid receptors in the gastric cytoprotective effects of opioids against ethanol-induced lesions.
  • To determine if specific mu-receptor agonists or antagonists influence the protective action of morphine.

Main Methods:

  • Administration of morphine, buprenorphine (a mu-partial agonist), loperamide (a gut-selective mu-agonist), and pentazocine (a mixed opioid with mu-antagonism) to rats.
  • Induction of gastric lesions using ethanol.
  • Assessment of the protective or aggravating effects of the tested opioids on gastric lesions.

Main Results:

  • Morphine exhibited significant protection against ethanol-induced gastric lesions.
  • Buprenorphine aggravated lesions at higher doses, and loperamide showed no protective effect.
  • Pentazocine, a mu-receptor antagonist, demonstrated protective effects on its own.
  • Naloxone, an opioid antagonist, reversed the protective effect of morphine.

Conclusions:

  • The findings suggest that mu-opioid receptors are not involved in the gastric cytoprotective action of opioids against ethanol-induced damage.
  • The mechanism underlying opioid-induced gastric protection likely involves other receptor systems.
  • Further research is needed to elucidate the specific pathways mediating opioid-induced gastroprotection.

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