Gastric cytoprotective effect of morphine is probably not mediated by mu-receptors.
Morphine has a significant protective effect on ethanol-induced gastric lesions. This effect is antagonized by naloxone, suggesting that it is mediated by opioid receptors. In the rat, mu-receptors have been shown to be involved in other gastrointestinal actions of opioids. However, the potent partial agonist at mu-receptors, buprenorphine, not only failed to protect but actually aggravated ethanol-induced lesions at higher doses. The gut-selective mu-agonist, loperamide, also did not have a protective effect, while the mixed opioid, pentazocine, which has an antagonistic action at mu-receptors, by itself protected against ethanol-induced gastric lesions. Our results suggest that mu-receptors are probably not involved in the gastric cytoprotective action of opioids.
Bhounsule
S A
SA
Department of Pharmacology, Goa Medical College, India.
D'Souza
R S
RS
Dhume
V G
VG
D000284:Administration, Oral; D000818:Animals; D002047:Buprenorphine / Q000008:administration & dosage / Q000494:pharmacology; D004195:Disease Models, Animal; D004347:Drug Interactions; D000431:Ethanol / Q000633:toxicity*; D007274:Injections, Intraperitoneal; D008139:Loperamide / Q000008:administration & dosage / Q000494:pharmacology; D008297:Male; D009020:Morphine / Q000008:administration & dosage / Q000494:pharmacology* / Q000627:therapeutic use; D009270:Naloxone / Q000008:administration & dosage / Q000494:pharmacology; D010423:Pentazocine / Q000008:administration & dosage / Q000494:pharmacology; D011897:Random Allocation; D051381:Rats; D017208:Rats, Wistar; D017450:Receptors, Opioid, mu / Q000187:drug effects* / Q000378:metabolism; D013270:Stomach / Q000166:cytology / Q000187:drug effects*; D013276:Stomach Ulcer / Q000139:chemically induced / Q000188:drug therapy
D017450:Receptors, Opioid, mu; D009270:Naloxone; D000431:Ethanol; D002047:Buprenorphine; D008139:Loperamide; D009020:Morphine; D010423:Pentazocine