title: Morphine noncompetitively inhibits [3H]leucine enkephalin binding to membranes lacking type-II delta binding sites: evidence for a two-site allosteric model.
abstract: Using the site-directed, delta-selective alkylating agent FIT (Rice et al., Science 220, 314-316, 1983), membranes devoid of detectable higher affinity delta binding sites were prepared. As compared to control membranes, the IC50 of morphine required to inhibit [3H]LE binding to FIT-treated membranes was two orders of magnitude lower. Further, morphine was a noncompetitive inhibitor of [3H]LE binding to FIT-treated membranes, supporting the notion that the lower affinity delta binding site is the delta binding site of the opiate receptor complex.
mesh_terms: D000494:Allosteric Regulation; D000818:Animals; D001667:Binding, Competitive; D001921:Brain / Q000187:drug effects / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D004743:Enkephalin, Leucine / Q000378:metabolism*; D005283:Fentanyl / Q000031:analogs & derivatives / Q000494:pharmacology; D017879:Isothiocyanates; D007700:Kinetics; D009020:Morphine / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains; D011957:Receptors, Opioid / Q000187:drug effects / Q000378:metabolism*; D017465:Receptors, Opioid, delta
chemical_list: D017879:Isothiocyanates; D011957:Receptors, Opioid; D017465:Receptors, Opioid, delta; D004743:Enkephalin, Leucine; D009020:Morphine; C037091:fentanyl isothiocyanate; D005283:Fentanyl