Muscarinic receptor binding in rat brain using the agonist, [3H]cis methyldioxolane

Frederick J. Ehlert, Yvon Dumont, William R. Roeske, Henry I. Yamamura

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Muscarinic receptor binding was measured in rat forebrain preparations using the muscarinic agonist, [3H]cis methyldioxolane ([3H]CD). The results of equilibrium binding studies using [3H]CD concentrations between 0.5-64 nM showed that [3H]CD binding did not saturate in this concentration range, although the binding isotherm was concave downward. Nonlinear regression analysis of the binding data revealed the presence of two populations of muscarinic receptors having dissociation constants of 1.83 and 123 nM and binding capacities of 85 and 1320 fmol/mg protein, respectively. Competitive inhibition experiments showed that [3H]CD binding was readily displaced by several muscarinic agonists and antagonists. The stereospecificity of [3H]CD binding was demonstrated in competitive inhibition experiments using the stereoisomers of benzetimide and acetyl-β-methylcholine. Dexetimide was 10,000 times more potent than levetimide and l-acetyl-β-methylcholine was 520 times more potent than d-acetyl-β-methylcholine. A variety of nonmuscarinic cholinergic drugs were not effective at inhibiting [3H]CD binding at a concentration of 10 μM.

Original languageEnglish (US)
Pages (from-to)961-967
Number of pages7
JournalLife Sciences
Issue number12
StatePublished - Mar 24 1980

ASJC Scopus subject areas

  • Biochemistry, Genetics and Molecular Biology(all)
  • Pharmacology, Toxicology and Pharmaceutics(all)


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