Interactions of agonists with an allosteric antagonist at muscarinic acetylcholine M2 receptors

Alfred Lanzafame, Arthur Christopoulos, Fred Mitchelson

Research output: Contribution to journalArticleResearchpeer-review

26 Citations (Scopus)

Abstract

The interaction of heptane-1,7-bis(dimethyl-3'-phthalimidopropylammonium bromide) (C7/3'-phth), with several agonists, was investigated at the muscarinic M2 receptor in guinea-pig left atria. C7/3'-phth shifted concentration-response curves for the agonists, carbachol, oxotremorine-M and (+)-cis-dioxolane, to the right in a parallel fashion. Arunlakshana-Schild regressions of the data yielded slopes significantly different to unity, suggesting non-competitive antagonism. Non-linear regression analysis, using an equation based on allosteric modulation, gave quantitative estimates of co-operativity (α values) and the dissociation constant of C7/3'-phth (K(B)). In all cases, the K(B) estimates for C7/3'-phth were not significantly different. Increasing the carbachol contact time 10-fold did not significantly influence the K(B) or the α value obtained with C7/3'-phth. Changing from Krebs to Tyrode solution did not significantly alter the K(B) for C7/3'-phth, although α values obtained were consistently lower in Tyrode solution, suggesting that the allosteric action may be sensitive to buffer composition. A 4-fold higher degree of negative, heterotropic co-operativity between C7/3'-phth and agonists than between C7/3'-phth and competitive antagonists was also found.

Original languageEnglish
Pages (from-to)27-32
Number of pages6
JournalEuropean Journal of Pharmacology
Volume316
Issue number1
DOIs
Publication statusPublished - 28 Nov 1996

Keywords

  • Bisquaternary allosteric antagonist
  • Muscarinic acetylcholine receptor agonist

Cite this

@article{36e8e991b759459bbe9fe5cf9f023b73,
title = "Interactions of agonists with an allosteric antagonist at muscarinic acetylcholine M2 receptors",
abstract = "The interaction of heptane-1,7-bis(dimethyl-3'-phthalimidopropylammonium bromide) (C7/3'-phth), with several agonists, was investigated at the muscarinic M2 receptor in guinea-pig left atria. C7/3'-phth shifted concentration-response curves for the agonists, carbachol, oxotremorine-M and (+)-cis-dioxolane, to the right in a parallel fashion. Arunlakshana-Schild regressions of the data yielded slopes significantly different to unity, suggesting non-competitive antagonism. Non-linear regression analysis, using an equation based on allosteric modulation, gave quantitative estimates of co-operativity (α values) and the dissociation constant of C7/3'-phth (K(B)). In all cases, the K(B) estimates for C7/3'-phth were not significantly different. Increasing the carbachol contact time 10-fold did not significantly influence the K(B) or the α value obtained with C7/3'-phth. Changing from Krebs to Tyrode solution did not significantly alter the K(B) for C7/3'-phth, although α values obtained were consistently lower in Tyrode solution, suggesting that the allosteric action may be sensitive to buffer composition. A 4-fold higher degree of negative, heterotropic co-operativity between C7/3'-phth and agonists than between C7/3'-phth and competitive antagonists was also found.",
keywords = "Bisquaternary allosteric antagonist, Muscarinic acetylcholine receptor agonist",
author = "Alfred Lanzafame and Arthur Christopoulos and Fred Mitchelson",
year = "1996",
month = "11",
day = "28",
doi = "10.1016/S0014-2999(96)00639-5",
language = "English",
volume = "316",
pages = "27--32",
journal = "European Journal of Pharmacology",
issn = "0014-2999",
publisher = "Elsevier",
number = "1",

}

Interactions of agonists with an allosteric antagonist at muscarinic acetylcholine M2 receptors. / Lanzafame, Alfred; Christopoulos, Arthur; Mitchelson, Fred.

In: European Journal of Pharmacology, Vol. 316, No. 1, 28.11.1996, p. 27-32.

Research output: Contribution to journalArticleResearchpeer-review

TY - JOUR

T1 - Interactions of agonists with an allosteric antagonist at muscarinic acetylcholine M2 receptors

AU - Lanzafame, Alfred

AU - Christopoulos, Arthur

AU - Mitchelson, Fred

PY - 1996/11/28

Y1 - 1996/11/28

N2 - The interaction of heptane-1,7-bis(dimethyl-3'-phthalimidopropylammonium bromide) (C7/3'-phth), with several agonists, was investigated at the muscarinic M2 receptor in guinea-pig left atria. C7/3'-phth shifted concentration-response curves for the agonists, carbachol, oxotremorine-M and (+)-cis-dioxolane, to the right in a parallel fashion. Arunlakshana-Schild regressions of the data yielded slopes significantly different to unity, suggesting non-competitive antagonism. Non-linear regression analysis, using an equation based on allosteric modulation, gave quantitative estimates of co-operativity (α values) and the dissociation constant of C7/3'-phth (K(B)). In all cases, the K(B) estimates for C7/3'-phth were not significantly different. Increasing the carbachol contact time 10-fold did not significantly influence the K(B) or the α value obtained with C7/3'-phth. Changing from Krebs to Tyrode solution did not significantly alter the K(B) for C7/3'-phth, although α values obtained were consistently lower in Tyrode solution, suggesting that the allosteric action may be sensitive to buffer composition. A 4-fold higher degree of negative, heterotropic co-operativity between C7/3'-phth and agonists than between C7/3'-phth and competitive antagonists was also found.

AB - The interaction of heptane-1,7-bis(dimethyl-3'-phthalimidopropylammonium bromide) (C7/3'-phth), with several agonists, was investigated at the muscarinic M2 receptor in guinea-pig left atria. C7/3'-phth shifted concentration-response curves for the agonists, carbachol, oxotremorine-M and (+)-cis-dioxolane, to the right in a parallel fashion. Arunlakshana-Schild regressions of the data yielded slopes significantly different to unity, suggesting non-competitive antagonism. Non-linear regression analysis, using an equation based on allosteric modulation, gave quantitative estimates of co-operativity (α values) and the dissociation constant of C7/3'-phth (K(B)). In all cases, the K(B) estimates for C7/3'-phth were not significantly different. Increasing the carbachol contact time 10-fold did not significantly influence the K(B) or the α value obtained with C7/3'-phth. Changing from Krebs to Tyrode solution did not significantly alter the K(B) for C7/3'-phth, although α values obtained were consistently lower in Tyrode solution, suggesting that the allosteric action may be sensitive to buffer composition. A 4-fold higher degree of negative, heterotropic co-operativity between C7/3'-phth and agonists than between C7/3'-phth and competitive antagonists was also found.

KW - Bisquaternary allosteric antagonist

KW - Muscarinic acetylcholine receptor agonist

UR - http://www.scopus.com/inward/record.url?scp=0030605219&partnerID=8YFLogxK

U2 - 10.1016/S0014-2999(96)00639-5

DO - 10.1016/S0014-2999(96)00639-5

M3 - Article

VL - 316

SP - 27

EP - 32

JO - European Journal of Pharmacology

JF - European Journal of Pharmacology

SN - 0014-2999

IS - 1

ER -