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The effect of allosteric antagonists in modulating muscarinic M 2 ‐receptor function in guinea‐pig isolated trachea
Author(s) -
Spina D.,
Minshall E.,
Goldie R.G.,
Page C.P.
Publication year - 1994
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1111/j.1476-5381.1994.tb13165.x
Subject(s) - muscarinic acetylcholine receptor , methacholine , ruthenium red , guinea pig , stimulation , acetylcholine , chemistry , endocrinology , medicine , receptor , histamine , allosteric regulation , biology , biochemistry , calcium , respiratory disease , lung
1 We have assessed the influence of a range of synthetic cationic polypeptides with putative inhibitory actions at prejunctional muscarinic M 2 ‐receptors on electrical field stimulation‐induced contraction of guinea‐pig isolated tracheal preparations. Electrical field stimulation of epithelium‐denuded guinea‐pig trachea resulted in frequency‐dependent contractile responses. As expected, tracheal smooth muscle sensitivity to electrical field stimulation was increased in tissues pretreated with the muscarinic M 2 ‐receptor antagonist, gallamine. In contrast, gallamine did not significantly alter the contractile potency to acetylcholine. 2 Unlike gallamine, the synthetic cationic polypeptides, poly‐ l ‐arginine, poly‐ l ‐lysine, poly‐ d ‐lysine, the cationic dye ruthenium red and the anionic polysaccharide, heparin, failed to increase significantly tracheal smooth muscle sensitivity to electrical field stimulation. 3 Poly‐ l ‐arginine, ruthenium red and heparin had no effect on the contractile response to exogenously applied methacholine. 4 These data are consistent with the concept that in guinea‐pig tracheal smooth muscle, gallamine is an allosteric antagonist of guinea‐pig tracheal muscarinic M 2 ‐receptors, whereas the various cationic polypeptides and the polyanion, heparin, are not.