Abstract
Atropine and scopolamine inhibit the binding of [3H] quinuclidinyl benzilate (QNB) to muscarinic receptors of rat forebrain in a manner that suggests homogeneity of the binding sites. Under the same conditions, the inhibition by N-methylatropine (NMA) and N-methylscopolamine (NMS) of the binding of [3H]QNB is consistent with the presence of subpopulations of receptors that differ greatly in affinities toward these quaternary ligands. The subpopulations that are defined according to the affinities of NMA and NMS correlate very well with those that are defined by the use of gallamine. It is suggested that the heterogeneity in the binding of NMS explains some of the anomalous interactions between NMS and gallamine that have been reported previously.
Publication types
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Allosteric Site
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Animals
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Atropine / pharmacology
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Atropine Derivatives / pharmacology
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Binding, Competitive
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Brain / metabolism
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Gallamine Triethiodide / pharmacology*
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In Vitro Techniques
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Male
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N-Methylscopolamine
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Parasympatholytics / pharmacology*
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Quinuclidinyl Benzilate / metabolism
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Rats
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Rats, Inbred Strains
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Receptors, Muscarinic / classification*
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Receptors, Muscarinic / drug effects
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Scopolamine / pharmacology
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Scopolamine Derivatives / pharmacology
Substances
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Atropine Derivatives
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Parasympatholytics
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Receptors, Muscarinic
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Scopolamine Derivatives
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Quinuclidinyl Benzilate
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Atropine
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methylatropine
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Scopolamine
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Gallamine Triethiodide
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N-Methylscopolamine