The binding of antagonists to brain muscarinic receptors
Hulme, E.C.; Birdsall, N.J.; Burgen, A.S.; Mehta, P.
Molecular Pharmacology 14(5): 737-750
1978
ISSN/ISBN: 0026-895X PMID: 714022 Document Number: 126055
The equilibrium binding of muscarinic antagonists [e.g., N-([3H]methyl)-atropinium iodide, N-(2,3[3H]propyl)-N,N-dimethyl-2-aminoethylbenzilate, N-([3H]-methyl)-scopolamine, [3H]atropine and [3H]quinuclidinylbenzilate] to a crude synaptosome fraction from rat cerebral cortex obeyed the simple Langmuir isotherm. The affinity constants measured range from 105-1010/M and in all cases agree within a factor of 3 with the corresponding values derived from measurements of anticholinergic potency on smooth muscle. The methodology which must be applied to obtain valid measurements of affinity constants from in vitro studies using radiolabeled ligands was discussed.