Abstract
The pharmacological properties of bisquaternary caracurine V, iso-caracurine V, and pyrazino[1,2-a;4,5-a']diindole analogues and of the neuromuscular blocking agents alcuronium and toxiferine I have been characterized at numerous ligand-gated ion channels. Several of the analogues are potent antagonists of the homomeric alpha7 nicotinic acetylcholine receptor (nAChR), displaying nanomolar binding affinities and inhibiting acetylcholine-evoked signaling through the receptor in a competitive manner. In contrast, they do not display activities at heteromeric neuronal nAChRs and only exhibit weak antagonistic activities at the related 5-HT3A serotonin receptor. In a mutagenesis study, five selected analogues have been demonstrated to bind to the orthosteric site of the alpha7 nAChR. The binding site of the compounds overlaps with that of the standard alpha7 antagonist methyllycaconitine, the binding of them being centered in a cation-pi interaction between the quaternary nitrogen atom of the ligand and the Trp149 residue in the receptor, with additional key contributions from other aromatic receptor residues such as Tyr188, Tyr195, and Trp55.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Aconitine / analogs & derivatives
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Aconitine / pharmacology
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Alkaloids / chemical synthesis*
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Alkaloids / chemistry
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Alkaloids / pharmacology
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Animals
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Binding Sites
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Binding, Competitive
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Cell Line
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Humans
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Ion Channels / drug effects
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Ion Channels / physiology
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Ligands
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Membrane Potentials / drug effects
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Mice
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Models, Molecular
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Molecular Structure
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Mutation
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Neurons / metabolism*
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Nicotinic Antagonists / chemical synthesis*
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Nicotinic Antagonists / chemistry
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Nicotinic Antagonists / pharmacology
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Radioligand Assay
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Rats
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Receptors, Nicotinic / drug effects*
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Receptors, Nicotinic / genetics
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Receptors, Nicotinic / metabolism
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Receptors, Serotonin, 5-HT3 / genetics
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Receptors, Serotonin, 5-HT3 / metabolism
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Recombinant Fusion Proteins / antagonists & inhibitors
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Recombinant Fusion Proteins / genetics
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Serotonin 5-HT3 Receptor Antagonists
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Structure-Activity Relationship
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alpha7 Nicotinic Acetylcholine Receptor
Substances
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Alkaloids
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Chrna7 protein, human
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Chrna7 protein, mouse
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Chrna7 protein, rat
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Ion Channels
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Ligands
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Nicotinic Antagonists
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Receptors, Nicotinic
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Receptors, Serotonin, 5-HT3
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Recombinant Fusion Proteins
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Serotonin 5-HT3 Receptor Antagonists
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alpha7 Nicotinic Acetylcholine Receptor
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methyllycaconitine
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caracurine V
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Aconitine