Two affinity states of M1 muscarine receptors

Cell Mol Neurobiol. 1988 Jun;8(2):181-91. doi: 10.1007/BF00711244.


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.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Binding, Competitive
  • Hippocampus / metabolism*
  • Kinetics
  • Oxotremorine / metabolism*
  • Pirenzepine / metabolism
  • Rabbits
  • Receptors, Muscarinic / metabolism*


  • Receptors, Muscarinic
  • Pirenzepine
  • Oxotremorine