title: Two affinity states of M1 muscarine receptors.
abstract: 1. The binding of oxotremorine-M to M1 muscarine receptors was examined by measuring competition between the agonist and 3H-pirenzepine, using rabbit hippocampal membranes suspended in 20 mM Tris buffer containing 1 mM Mn2+. 2. Both ligands interacted with a single class of receptors. The receptors could assume two affinity states for oxotremorine-M, with equal numbers of high-affinity (KH) and low-affinity (KL) sites. 3. KH interconverted reversibly to KL in the absence of divalent cations and interconverted reversibly to a state similar to KL in the presence of guanyl 5'-yl imidodiphosphate. 4. The results are compatible with a model in which a pair of receptor molecules can be stabilized by a guanine nucleotide-binding "G protein" and have one site each of KH and KL affinity.
authors.affiliation: Department of Pharmacology, University of Miami School of Medicine, Florida 33101.
authors.forename: L T
authors.initials: LT
authors.lastname: Potter
authors.forename: C A
authors.initials: CA
authors.lastname: Ferrendelli
authors.forename: H E
authors.initials: HE
authors.lastname: Hanchett
mesh_terms: D000818:Animals; D001667:Binding, Competitive; D006624:Hippocampus / Q000378:metabolism*; D007700:Kinetics; D010095:Oxotremorine / Q000378:metabolism*; D010890:Pirenzepine / Q000378:metabolism; D011817:Rabbits; D011976:Receptors, Muscarinic / Q000378:metabolism*
chemical_list: D011976:Receptors, Muscarinic; D010890:Pirenzepine; D010095:Oxotremorine