Seven esters of alpha-truxillic acid have been synthesized: bis-3-piperidylpropyl ester and its quaternary bis-N-ethyl derivative, bis-N-diethylaminopropyl ester and its quaternary bis-N-methyl derivative, and bis-4-piperidylbutyl ester and its quaternary bis-N-methyl and bis-N-ethyl derivatives. All esters inhibited the specific binding of muscarinic receptor antagonist [methyl-3H]-N-methylscopolamine ([3H]-NMS) to muscarinic receptors in membranes of CHO cell lines stably expressing the human gene for the M1, M2, M3 or M4 subtype of muscarinic receptors. All esters displayed the highest potency at the M2 and the lowest potency at the M3 receptor subtype. In experiments performed on the M2 muscarinic receptor subtype, the affinity between the receptors and the esters was greatly increased when the concentration of ions was diminished. The highest affinities were found for the tertiary bis-3-piperidylpropyl and bis-4-piperidylbutyl aminoesters (equilibrium dissociation constants of 52 and 179 pM, respectively, in the low ionic strength medium). All investigated esters slowed down the dissociation of [3H]-NMS from the M2 muscarinic receptor subtype. [3H]-NMS dissociation from the M1, M3 and M4 muscarinic receptor subtypes was investigated in experiments with the bis-4-piperidylbutyl aminoester and also found to be decelerated. It is concluded that the esters of alpha-truxillic acid act as M2-selective allosteric modulators of muscarinic receptors and that, by their potency, the tertiary bis-3-piperidylpropyl and bis-4-piperidylbutyl aminoesters surpass the other known allosteric modulators of these receptors.

• MeSH
• Allosteric Regulation MeSH
• Muscarinic Antagonists metabolism   pharmacology   MeSH
• CHO Cells MeSH
• Cyclobutanes pharmacology   MeSH
• Cricetinae MeSH
• Humans MeSH
• N-Methylscopolamine metabolism   MeSH
• Receptors, Muscarinic classification   drug effects   MeSH
• Tritium MeSH
• Animals MeSH
• Check Tag
• Cricetinae MeSH
• Humans MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Research Support, U.S. Gov't, P.H.S. MeSH
• Names of Substances
• Muscarinic Antagonists MeSH
• Cyclobutanes MeSH
• N-Methylscopolamine MeSH
• Receptors, Muscarinic MeSH
• Tritium MeSH
• truxillic acid MeSH Browser

Ligands that bind to the allosteric-binding sites on muscarinic acetylcholine receptors alter the conformation of the classical-binding sites of these receptors and either diminish or increase their affinity for muscarinic agonists and classical antagonists. It is not known whether the resulting conformational change also affects the interaction between the receptors and the G proteins. We have now found that the muscarinic receptor allosteric modulators alcuronium, gallamine, and strychnine (acting in the absence of an agonist) alter the synthesis of cAMP in Chinese hamster ovary (CHO) cells expressing the M2 or the M4 subtype of muscarinic receptors in the same direction as the agonist carbachol. In addition, most of their effects on the production of inositol phosphates in CHO cells expressing the M1 or the M3 muscarinic receptor subtypes are also similar to (although much weaker than) those of carbachol. The agonist-like effects of the allosteric modulators are not observed in CHO cells that have not been transfected with the gene for any of the subtypes of muscarinic receptors. The effects of alcuronium on the formation of cAMP and inositol phosphates are not prevented by the classical muscarinic antagonist quinuclidinyl benzilate. These observations demonstrate for the first time that the G protein-mediated functional responses of muscarinic receptors can be evoked not only from their classical, but also from their allosteric, binding sites. This represents a new mechanism of receptor activation.

• MeSH
• Muscarinic Agonists pharmacology   MeSH
• Alcuronium pharmacology   MeSH
• Allosteric Regulation MeSH
• Cyclic AMP metabolism   MeSH
• Muscarinic Antagonists pharmacology   MeSH
• Quinuclidinyl Benzilate pharmacology   MeSH
• CHO Cells MeSH
• Inositol Phosphates physiology   MeSH
• Cricetinae MeSH
• Periodicity MeSH
• GTP-Binding Proteins physiology   MeSH
• Receptors, Muscarinic physiology   MeSH
• Recombinant Proteins MeSH
• Signal Transduction MeSH
• Strychnine pharmacology   MeSH
• Transfection MeSH
• Gallamine Triethiodide pharmacology   MeSH
• Animals MeSH
• Check Tag
• Cricetinae MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Research Support, U.S. Gov't, P.H.S. MeSH
• Names of Substances
• Muscarinic Agonists MeSH
• Alcuronium MeSH
• Cyclic AMP MeSH
• Muscarinic Antagonists MeSH
• Quinuclidinyl Benzilate MeSH
• Inositol Phosphates MeSH
• GTP-Binding Proteins MeSH
• Receptors, Muscarinic MeSH
• Recombinant Proteins MeSH
• Strychnine MeSH
• Gallamine Triethiodide MeSH