The opiate receptor binding interactions of 3H-methionine enkephalin, an opioid peptide

Rabi Simantov, Steven R. Childers, Solomon H. Snyder

Research output: Contribution to journalArticlepeer-review

100 Scopus citations


3H-Methionine enkephalin binds stereospecifically with high affinity to opiate receptors in rat brain membranes. Equilibrium experiments indicate two distinct dissociation constants with KD values of 1.8 and 5.8 nM respectively. 3H-Methionine enkephalin associates and dissociates from the opiate receptor with 8-10 fold slower kinetics that 3H-opiates. Though several opiates have similar affinities for sites labeled by 3H-methionine enkephalin, 3H-dihydromorphine and 3H-naloxone, some opiates such as morphine, dihydromorphine and oxymorphone are only one tenth as potent in competing for 3H-methionine enkephalin as for 3H-dihydromorphine and 3H-naloxone binding. As with other opiate agonists, 5-10 mM sodium selectively decreases the binding of 3H-methionine enkephalin. At 26°C, 0.1-1.0 mM managanese but not magnesium or calcium increases the binding of 3H-methionine enkephalin, while at 0°C managanese decreases the binding of methionine enkephalin.

Original languageEnglish (US)
Pages (from-to)319-331
Number of pages13
JournalEuropean Journal of Pharmacology
Issue number3
StatePublished - Feb 1 1978


  • Enkephalin
  • Morphine
  • Naloxone
  • Opiate receptor
  • Opiates

ASJC Scopus subject areas

  • Pharmacology


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