Abstract
Binding sites with high affinity and specificity for [(3)H]quinuclidinyl benzilate (QNB) are present in homogenates of rat brain. The characteristics of the binding sites resemble those of muscarinic cholinergic receptors. Specific binding is saturable with respect to [(3)H]QNB and tissue concentration and is time-, temperature-, and pH-dependent. The bimolecular rate of association (2.0 x 10(8) M(-1) min(-1)) and dissociation (1.2 x 10(-2) min(-1)) at 35 degrees indicate a dissociation constant of 60 pM and a density of 65 pmol/g of brain. Muscarinic antagonists and agonists displace specific [(3)H]QNB binding, while nicotinic and non-cholinergic drugs possess little affinity for [(3)H]QNB-binding sites.
MeSH terms
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Acetylcholine / pharmacology
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Animals
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Arecoline / pharmacology
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Atropine / pharmacology
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Benzilates / metabolism*
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Binding Sites
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Binding, Competitive
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Brain / metabolism*
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Brompheniramine / pharmacology
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Carbachol / pharmacology
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Chlorpheniramine / pharmacology
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Hydrogen-Ion Concentration
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In Vitro Techniques
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Kinetics
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Male
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Methacholine Compounds / pharmacology
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Microsomes / metabolism
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Mitochondria / metabolism
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Oxotremorine / metabolism*
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Pilocarpine / pharmacology
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Quaternary Ammonium Compounds / pharmacology
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Quinuclidines / metabolism*
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Rats
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Receptors, Cholinergic*
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Scopolamine / pharmacology
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Temperature
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Time Factors
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Tritium
Substances
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Benzilates
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Methacholine Compounds
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Quaternary Ammonium Compounds
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Quinuclidines
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Receptors, Cholinergic
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Pilocarpine
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Tritium
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Chlorpheniramine
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Arecoline
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Oxotremorine
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Atropine
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Carbachol
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Scopolamine
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Brompheniramine
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Acetylcholine