Hulme_1983_Eur.J.Pharmacol_94_59

EDTA treatment of membrane preparations from rat brain and myocardium reduced the relative proportion of superhigh and high affinity binding sites for muscarinic agonists by up to 60%. This effect was partially or completely reversed by millimolar concentrations of Mg2+ or Mn2+. A number of multivalent metal cations gave qualitatively similar effects, yielding stimulation of agonist binding at low concentrations but inhibition at higher concentrations. The divalent cation-linked subpopulation of muscarinic agonist binding sites identified in this study appears to be the primary target for guanine nucleotide inhibition.