A very high affinity opioid binding site in rat brain: demonstration by computer modeling

Biochem Biophys Res Commun. 1984 Jul 18;122(1):265-9. doi: 10.1016/0006-291x(84)90469-8.


We present substantial new evidence for at least four distinct types of opioid receptors in rat brain, using quantitative ligand binding studies and mathematical modeling. Three of these binding sites are consistent with the well established "mu", "delta" and "kappa" receptors. The fourth has two distinctive features: 1) extremely high affinity (dissociation constant less than 1 nM); 2) almost complete lack of specificity for the classical "delta" or "mu" selective ligands. These properties are consistent with the putative "mu1" receptor described by Pasternak and coworkers.

MeSH terms

  • Animals
  • Binding, Competitive
  • Brain Chemistry*
  • Computers
  • Enkephalin, Ala(2)-MePhe(4)-Gly(5)-
  • Enkephalin, Leucine / analogs & derivatives
  • Enkephalin, Leucine / metabolism
  • Enkephalin, Leucine-2-Alanine
  • Enkephalins / metabolism
  • Mathematics
  • Models, Chemical
  • Naloxone / metabolism
  • Rats
  • Rats, Inbred Strains
  • Receptors, Opioid / analysis*


  • Enkephalins
  • Receptors, Opioid
  • Enkephalin, Ala(2)-MePhe(4)-Gly(5)-
  • Naloxone
  • Enkephalin, Leucine
  • Enkephalin, Leucine-2-Alanine