title: Differential properties of mu and delta opiate binding sites studied with highly selective ligands.
abstract: Differences in binding kinetics, ions and nucleotides interactions with rat brain opiate mu and delta receptor subtypes were investigated using respectively DAGO (Tyr-D-Ala-Gly-MePhe-Gly-ol) and DTLET (Tyr-D-Thr-Gly-Phe-Leu-Thr) as highly selective mu and delta ligands. On the basis of kinetic experiments the delta-agonist binding is an extremely slow process as compared to that of the mu-agonist. Displacement experiments by DTLET of [3H] DAGO binding and Scatchard analysis of the binding of [3H] DTLET in the absence and presence of DAGO demonstrated that an independent model of interaction to two independent sites best describes the observed data. Steady state binding of [3H] DAGO is decreased by GMP-P(NH)P while this nucleotide is ineffective in reducing the binding of DTLET. However in presence of NaCl, GMP-P(NH)P reduces the specific binding at both sites in a concentration dependent manner. The analysis of the nucleotide inhibition of delta-binding at various concentrations of NaCl suggests that the non-hydrolyzable nucleotide can exerts its effects only on a prebound Na+ receptor. These data suggest that mu and delta-receptors may assume different affinity states depending upon the presence of Na+ and nucleotide.
mesh_terms: D000818:Animals; D001667:Binding, Competitive; D001921:Brain / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D020875:Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; D004745:Enkephalins / Q000378:metabolism*; D007700:Kinetics; D008297:Male; D009842:Oligopeptides; D051381:Rats; D011957:Receptors, Opioid / Q000378:metabolism*; D017465:Receptors, Opioid, delta; D017450:Receptors, Opioid, mu
chemical_list: D004745:Enkephalins; D009842:Oligopeptides; D011957:Receptors, Opioid; D017465:Receptors, Opioid, delta; D017450:Receptors, Opioid, mu; D020875:Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; C037653:deltakephalin