Central and peripheral involvement of endogenous opioid peptides in gastric protection in stressed rats.
The effects of intraperitoneal and intracerebroventricular administration of the inhibitor of endopeptidase EC 24.11 (enkephalinase), thiorphan, and the synthetic enkephalin analogue [D-Ala2-Met5]enkephalinamide (DALA) were investigated in cold-restraint-stressed rats. Drugs were administered alone or after pretreatment with naloxone or naloxone methiodide given 20 min prior to the drugs. Thiorphan and DALA, administered centrally (4 micrograms i.c.v./rat) or peripherally (400 micrograms/kg), induced a significant gastric protection. Prior treatment with naloxone s.c. (1 mg/kg) inhibited the effect induced by i.c.v. or i.p. injections of thiorphan or DALA. In contrast, s.c. administration of naloxone methiodide (1 mg/kg) did not affect the response induced by central administration of thiorphan or DALA, but was able to prevent that of thiorphan or DALA when they were administered i.p. These data strongly support the hypothesis of a central and peripheral involvement of endogenous opioid peptides in gastric protection in stressed rats.
Scoto
G M
GM
Institute of Pharmacology and Pharmacognosy, University of Catania, Italy.
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D000704:Analysis of Variance; D000818:Animals; D003080:Cold Temperature / Q000009:adverse effects; D004744:Enkephalin, Methionine / Q000031:analogs & derivatives* / Q000494:pharmacology; D005753:Gastric Mucosa / Q000187:drug effects* / Q000293:injuries; D007274:Injections, Intraperitoneal; D007276:Injections, Intraventricular; D007279:Injections, Subcutaneous; D008297:Male; D009270:Naloxone / Q000008:administration & dosage / Q000031:analogs & derivatives / Q000494:pharmacology; D009292:Narcotic Antagonists / Q000008:administration & dosage / Q000494:pharmacology; D011480:Protease Inhibitors / Q000494:pharmacology*; D000644:Quaternary Ammonium Compounds; D051381:Rats; D017207:Rats, Sprague-Dawley; D011957:Receptors, Opioid / Q000187:drug effects*; D013312:Stress, Physiological; D015244:Thiorphan / Q000494:pharmacology*
D009292:Narcotic Antagonists; D011480:Protease Inhibitors; D000644:Quaternary Ammonium Compounds; D011957:Receptors, Opioid; D009270:Naloxone; D004744:Enkephalin, Methionine; C022118:enkephalinamide-Met, Ala(2)-; C041269:N-methylnaloxone; D015244:Thiorphan