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Updated: Aug 9, 2026

Subcutaneous Administration of Muscarinic Antagonists and Triple-Immunostaining of the Levator Auris Longus Muscle in Mice
Published on: September 8, 2011
Method for comparing selectivities of unlabeled subpopulation-selective ligands: application to muscarinic receptors
1Department of Psychiatry, University of Vermont, Burlington 05405.
Abstract:
A method for comparing the selectivities of two unlabeled ligands by simultaneous competition for the binding of a nonselective labeled ligand has been illustrated by computer simulations. Experimental application of this approach indicated that the subpopulations of muscarinic receptors that are distinguished by the use of quaternary antagonists are not related to the M1 and M2 subtypes (based on pirenzepine). However, the quaternary agonist carbachol was found to express both modes of selectivity. The method should be particularly useful in the evaluation of new ligands when labeled selective ligands are unavailable. Further, this method complements experiments that can be carried out with a labeled selective ligand, since it emphasizes the contribution of the sites for which the selective ligand has low affinity.
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