title: Computer-assisted analysis of receptor-binding studies of [3H]-naloxone and [3H]-DADL: a reinterpretation of the Na+ effect.
abstract: Computer-assisted analysis of competitive binding studies of [3H]-naloxone, [3H]-DADL, morphine and meperidine in the presence and absence of 100 mM NaCl have been made. The results are most consistent with a 3-site model of opiate receptors and indicate that in the presence of Na+ naloxone changes from a mu-specific (81%) to a more kappa-specific (63%) ligand. The large IC50 shift in inhibition of [3H]-naloxone by three agonists, DADL, morphine and meperidine is found not to be due to a decrease in affinity at any receptor site but rather to a low affinity of these agonists at "kappa" in the presence of Na+.
mesh_terms: D000818:Animals; D001921:Brain / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D004743:Enkephalin, Leucine / Q000031:analogs & derivatives* / Q000378:metabolism; D016308:Enkephalin, Leucine-2-Alanine; D007700:Kinetics; D009270:Naloxone / Q000378:metabolism*; D051381:Rats; D011957:Receptors, Opioid / Q000187:drug effects / Q000378:metabolism*; D012964:Sodium / Q000494:pharmacology*
chemical_list: D011957:Receptors, Opioid; D009270:Naloxone; D004743:Enkephalin, Leucine; D016308:Enkephalin, Leucine-2-Alanine; D012964:Sodium