Novel allosteric effects of amiodarone at the muscarinic M5 receptor

Edward Stahl, John Ellis

Research output: Contribution to journalArticle

13 Citations (Scopus)

Abstract

Allosteric sites on muscarinic receptors may present superior therapeutic targets for several central nervous system disorders, due to the potential of allosteric ligands to provide more selective modulation and to preserve the spatiotemporal patterning that is characteristic of synaptic transmission. We have found that the antiarrhythmic drug amiodarone interacts allosterically with M1 and M5 muscarinic receptors. At both M1 and M5, amiodarone was only able to partially inhibit the binding of the orthosteric antagonist [3H]N-methylscopolamine (NMS). In addition, amiodarone was able to alter the rate of dissociation of [3H]NMS from M1 and M5 receptors. These findings suggest that NMS and amiodarone are able to bind to the receptor simultaneously. The pharmacology of the effect on NMS dissociation demonstrated that amiodarone was not interacting at the "common" site at which gallamine, obidoxime, and many other muscarinic allosteric ligands are known to bind. In functional studies, amiodarone enhanced the ability of acetylcholine (at EC20) to activate the M5 receptor; however, under the same conditions, amiodarone did not enhance M1 activation. More detailed studies at M5 found that the effect of amiodarone was to enhance the efficacy of acetylcholine, without increasing its potency. This report describes the first demonstration of allosteric enhancement of efficacy at the M5 receptor, and the first demonstration of enhancement of efficacy but not potency at any muscarinic receptor. In summary, amiodarone has been shown to be a novel positive allosteric modulator of muscarinic receptors that is selective for the M5 subtype, relative to M1.

Original languageEnglish (US)
Pages (from-to)214-222
Number of pages9
JournalJournal of Pharmacology and Experimental Therapeutics
Volume334
Issue number1
DOIs
StatePublished - Jul 1 2010

Fingerprint

Muscarinic M5 Receptors
Amiodarone
N-Methylscopolamine
Muscarinic Receptors
Acetylcholine
Obidoxime Chloride
Muscarinic M1 Receptors
Gallamine Triethiodide
Allosteric Site
Ligands
Anti-Arrhythmia Agents
Central Nervous System Diseases
Synaptic Transmission
Cholinergic Agents

All Science Journal Classification (ASJC) codes

  • Molecular Medicine
  • Pharmacology

Cite this

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abstract = "Allosteric sites on muscarinic receptors may present superior therapeutic targets for several central nervous system disorders, due to the potential of allosteric ligands to provide more selective modulation and to preserve the spatiotemporal patterning that is characteristic of synaptic transmission. We have found that the antiarrhythmic drug amiodarone interacts allosterically with M1 and M5 muscarinic receptors. At both M1 and M5, amiodarone was only able to partially inhibit the binding of the orthosteric antagonist [3H]N-methylscopolamine (NMS). In addition, amiodarone was able to alter the rate of dissociation of [3H]NMS from M1 and M5 receptors. These findings suggest that NMS and amiodarone are able to bind to the receptor simultaneously. The pharmacology of the effect on NMS dissociation demonstrated that amiodarone was not interacting at the {"}common{"} site at which gallamine, obidoxime, and many other muscarinic allosteric ligands are known to bind. In functional studies, amiodarone enhanced the ability of acetylcholine (at EC20) to activate the M5 receptor; however, under the same conditions, amiodarone did not enhance M1 activation. More detailed studies at M5 found that the effect of amiodarone was to enhance the efficacy of acetylcholine, without increasing its potency. This report describes the first demonstration of allosteric enhancement of efficacy at the M5 receptor, and the first demonstration of enhancement of efficacy but not potency at any muscarinic receptor. In summary, amiodarone has been shown to be a novel positive allosteric modulator of muscarinic receptors that is selective for the M5 subtype, relative to M1.",
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Novel allosteric effects of amiodarone at the muscarinic M5 receptor. / Stahl, Edward; Ellis, John.

In: Journal of Pharmacology and Experimental Therapeutics, Vol. 334, No. 1, 01.07.2010, p. 214-222.

Research output: Contribution to journalArticle

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