Inhibition of gastrointestinal transit by morphine and FK 33-824 in the rat and comparative narcotic antagonist properties of naloxone and its n-methyl quaternary analog

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

Research output: Contribution to journalArticle

22 Citations (Scopus)

Abstract

Morphine and the enkephalin-like peptide FK 33-824 given i.p. to rats potently inhibit gastrointestinal transit of a charcoal test meal, the doses inhibiting transit by 50% being respectively about 10 and 1 μg/kg. These intestinal effects are opiate-specific, locally elicited and presumably involve the same action site since they are reversed by the "peripherally selective" narcotic antagonist N-methyl naloxone with apparent pA2 values of 7.34 and 7.10 respectively against morphine and FK 33-824. The calculated pA2 value for naloxone/morphine with the same in vivo test procedure (8.83) and the relative ability of naloxone and N-methyl naloxone to prevent 3H-etorphine binding to rat brain membranes (IC50 43 and 541 nM), indicate different potency ratios between the two narcotic antagonists in the in vitro binding cell-free system (about 1:10) and in vivo (about 1:30), but the latter ratio agrees with published findings in the isolated guinea pig ileum.

Original languageEnglish
Pages (from-to)1271-1274
Number of pages4
JournalLife Sciences
Volume31
Issue number12-13
DOIs
Publication statusPublished - 1982

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D-Ala(2),MePhe(4),Met(0)-ol-enkephalin
Gastrointestinal Transit
Narcotic Antagonists
Naloxone
Morphine
Rats
Opiate Alkaloids
Etorphine
Cell-Free System
Enkephalins
Charcoal
Ileum
Inhibitory Concentration 50
Meals
Brain
Guinea Pigs
Membranes
Peptides

ASJC Scopus subject areas

  • Pharmacology

Cite this

Inhibition of gastrointestinal transit by morphine and FK 33-824 in the rat and comparative narcotic antagonist properties of naloxone and its n-methyl quaternary analog. / Manara, L.; Bianchi, G.; Fiocchi, R.; Notarnicola, A.; Peracchia, F.; Tavani, A.

In: Life Sciences, Vol. 31, No. 12-13, 1982, p. 1271-1274.

Research output: Contribution to journalArticle

Manara, L. ; Bianchi, G. ; Fiocchi, R. ; Notarnicola, A. ; Peracchia, F. ; Tavani, A. / Inhibition of gastrointestinal transit by morphine and FK 33-824 in the rat and comparative narcotic antagonist properties of naloxone and its n-methyl quaternary analog. In: Life Sciences. 1982 ; Vol. 31, No. 12-13. pp. 1271-1274.
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N2 - Morphine and the enkephalin-like peptide FK 33-824 given i.p. to rats potently inhibit gastrointestinal transit of a charcoal test meal, the doses inhibiting transit by 50% being respectively about 10 and 1 μg/kg. These intestinal effects are opiate-specific, locally elicited and presumably involve the same action site since they are reversed by the "peripherally selective" narcotic antagonist N-methyl naloxone with apparent pA2 values of 7.34 and 7.10 respectively against morphine and FK 33-824. The calculated pA2 value for naloxone/morphine with the same in vivo test procedure (8.83) and the relative ability of naloxone and N-methyl naloxone to prevent 3H-etorphine binding to rat brain membranes (IC50 43 and 541 nM), indicate different potency ratios between the two narcotic antagonists in the in vitro binding cell-free system (about 1:10) and in vivo (about 1:30), but the latter ratio agrees with published findings in the isolated guinea pig ileum.

AB - Morphine and the enkephalin-like peptide FK 33-824 given i.p. to rats potently inhibit gastrointestinal transit of a charcoal test meal, the doses inhibiting transit by 50% being respectively about 10 and 1 μg/kg. These intestinal effects are opiate-specific, locally elicited and presumably involve the same action site since they are reversed by the "peripherally selective" narcotic antagonist N-methyl naloxone with apparent pA2 values of 7.34 and 7.10 respectively against morphine and FK 33-824. The calculated pA2 value for naloxone/morphine with the same in vivo test procedure (8.83) and the relative ability of naloxone and N-methyl naloxone to prevent 3H-etorphine binding to rat brain membranes (IC50 43 and 541 nM), indicate different potency ratios between the two narcotic antagonists in the in vitro binding cell-free system (about 1:10) and in vivo (about 1:30), but the latter ratio agrees with published findings in the isolated guinea pig ileum.

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