Central and peripheral inhibition of gastrointestinal transit in rats: Narcotics differ substantially by acting at either or both levels

F. Peracchia, G. Bianchi, R. Fiocchi, P. Petrillo, A. Tavani, L. Manara

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The roles of local intestinal and centrally mediated opiate-specific mechanisms underlying gastrointestinal transit inhibition by five typical narcotic analgesics were assessed by the rat charcoal meal test. The doses (mg kg-1 s.c.) reducing the progression of charcoal to 50% of drug-free controls in 5 min (ID50) were approximately 1 for morphine and methadone, 0.5 and 40 for diamorphine and pethidine (all given 25 min before charcoal) and 0.001 for etorphine (10 min before charcoal). The delay in test meal travel caused by these ID50 doses was completely prevented by i.p. naloxone. Intracerebroventricular (i.c.v.) naloxone fully antagonized pethidine and etorphine but had no effect on morphine. Morphine, but neither pethidine nor etorphine, was antagonized by i.p. N-methyl naloxone (a peripheral antagonist). Diamorphine and methadone were partially antagonized by i.c.v. naloxone or i.p. N-methyl naloxone.

Original languageEnglish
Pages (from-to)699-701
Number of pages3
JournalJournal of Pharmacy and Pharmacology
Issue number10
Publication statusPublished - 1984


ASJC Scopus subject areas

  • Pharmacology
  • Pharmaceutical Science

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