Differential effect of humoral endorphin on the binding of opiate agonists and antagonists

Yosef Sarne, Yosef Itzhak, Ora Keren

Research output: Contribution to journalArticlepeer-review

7 Scopus citations


Humoral (H) endorphin, a novel endogenous factor with opiate-like activity was further characterized using various radioreceptor assays. H-Endorphin displaced both labelled opiates (morphine, ethylketazocine) and opioid peptides (leucine-enkephalin) from their specific binding sites in rat brain membranes. The effect of sodium ions on H-endorphin indicates its agonistic nature which is in agreement with previous pharmacological experiments. However, H-endorphin potentiated the binding of the opiate antagonist naloxone to brain membranes. This peculiar effect of H-endorphin on naloxone, together with the non-conventional interactions observed in various pharmacological assays, clearly distinguishes H-endorphin from other opioid ligands. A multisite model of the opiate receptor is presented. This model, which is compatible with the well documented evidence for receptors heterogeneity also explains non-conventional interactions between various opioid ligands.

Original languageEnglish (US)
Pages (from-to)227-235
Number of pages9
JournalEuropean Journal of Pharmacology
Issue number2
StatePublished - Jul 9 1982
Externally publishedYes


  • Endorphins
  • Multisite model of receptors
  • Opiate receptor
  • Opiates

ASJC Scopus subject areas

  • Cellular and Molecular Neuroscience
  • Pharmacology


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