Two affinity states of M1 muscarine receptors.
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.
Potter
L T
LT
Department of Pharmacology, University of Miami School of Medicine, Florida 33101.
Ferrendelli
C A
CA
Hanchett
H E
HE
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*
D011976:Receptors, Muscarinic; D010890:Pirenzepine; D010095:Oxotremorine