Evidence for morphine and morphine-like alkaloid responses resistant to naloxone blockade in the rat vas deferens

H. Miranda, F. Huidobro, J. Pablo Huidobro-Toro

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39 Citations (Scopus)

Abstract

The application of morphine or surrogates to the isolated rat vas deferens maintained at 37° C in Tyrode solution, produced an increase in the electrically induced muscular twitch. In contrast, leucine enkephalin or D-alanine2methionine enkephalinamide produced a dose-dependent inhibition of the muscular twitch. The effect of morphine and derivatives was not antagonized by naloxone, but the depression caused by the opiate pentapeptides or β-Endorphin was readily antagonized and reversed by naloxone. Tolerance developed to the in vitro effect of morphine; vasa deferentia obtained from tolerant-dependent rats were about six times less sensitive to the effect of morphine and about five times less sensitive to the depression caused by leucine enkephalin as compared to their respective paired, placebo implanted control rats.

Original languageEnglish
Pages (from-to)1511-1518
Number of pages8
JournalLife Sciences
Volume24
Issue number16
DOIs
Publication statusPublished - 16 Apr 1979

ASJC Scopus subject areas

  • General Medicine
  • General Biochemistry,Genetics and Molecular Biology
  • Pharmacology, Toxicology and Pharmaceutics(all)

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