Evidence for both inhibitory and excitatory effects of morphine on gastric secretion in the rat.
The relationship between a wide range of doses of i.p. morphine and the effects of gastric secretion in several rat experimental models was investigated. In unoperated rats, morphine 5-15 mg/kg dose-dependently decreased gastric acidity, but an excitatory effect was observed with 0.5-1.5 mg/kg. A dose-dependent inhibition was also obtained in conscious pylorus-ligated rats with morphine 5-15 mg/kg, whereas no significant effects were found at lower doses. By contrast, acid concentration was enhanced with morphine 0.5-15 mg/kg in anaesthetized pylorus-ligated rats and in stomach lumen perfused rats. The changes of pepsin concentration correlated with the changes in gastric secretory volume. An increase in the volume was associated with a decrease in pepsin concentration, while pepsin amount per stomach was dose-dependently increased in all the conditions under which morphine increased gastric acidity. All the effects of morphine on acid and pepsin secretion were prevented by naloxone 1 mg/kg i.p. Overall results indicate that morphine may induce both excitatory and inhibitory effects on gastric secretion in the rat: these effects depend on the dose of morphine and the experimental conditions.
Del Tacca
M
M
Institute of Medical Pharmacology, University of Pisa, Italy.
Bernardini
M C
MC
Corsano
E
E
Martinotti
E
E
Rozé
C
C
D000758:Anesthesia; D000818:Animals; D004305:Dose-Response Relationship, Drug; D005744:Gastric Acid / Q000378:metabolism; D005753:Gastric Mucosa / Q000187:drug effects / Q000378:metabolism*; D007276:Injections, Intraventricular; D008297:Male; D009020:Morphine / Q000008:administration & dosage / Q000494:pharmacology*; D010434:Pepsin A / Q000378:metabolism; D010477:Perfusion; D011708:Pylorus / Q000502:physiology; D051381:Rats; D011919:Rats, Inbred Strains
D009020:Morphine; D010434:Pepsin A