Muscarinic M1, M2 receptor binding. Relationship with functional efficacy.
Article Details
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Freedman SB, Beer MS, Harley EA
Muscarinic M1, M2 receptor binding. Relationship with functional efficacy.
Eur J Pharmacol. 1988 Oct 26;156(1):133-42.
- PubMed ID
- 3208836 [ View in PubMed]
- Abstract
A comparison has been made between [3H]pirenzepine binding to the M1 receptor population of rat cerebral cortex and [3H]N-methylscopolamine binding to M2 receptors in rat cardiac membranes. Several standard muscarinic antagonists including trihexyphenidyl HCl, benztropine, biperidin and 4-DAMP (4-diphenylacetoxy-N-methyl piperidine methiodide) showed some selectivity for the M1 binding assay. Dicyclomine and hexahydrosiladifenidol were the only antagonists with a selectivity approaching that of pirenzepine. Gallamine and AFDX-116 were the only M2 (cardiac) selective antagonists. Muscarinic agonists displayed profiles which could be classified into two groups, apparently related to their intrinsic activity. One group displayed apparent selectivity for the heart, with low Hill coefficients and contained full agonists such as acetylcholine. The second group displayed less selectivity, intermediate Hill coefficients and contained partial agonists such as pilocarpine. Thus muscarinic agents can distinguish between different tissues not only on the basis of receptor selectivity, but also by recognition of high and low agonist affinity states. Thus the intrinsic activity of a muscarinic agonist may reflect an apparent but not true receptor-mediated selectivity.
DrugBank Data that Cites this Article
- Drug Targets
Drug Target Kind Organism Pharmacological Action Actions Trihexyphenidyl Muscarinic acetylcholine receptor M1 Protein Humans YesAntagonistDetails Trihexyphenidyl Muscarinic acetylcholine receptor M2 Protein Humans UnknownAntagonistDetails Trihexyphenidyl Muscarinic acetylcholine receptor M3 Protein Humans UnknownAntagonistDetails