Author:
Bellido I.,Gómez A.,Cuesta F. Sánchez de la,Fernández J. L.
Abstract
Cholinergic agonists and antagonists frequently used for gastrointestinal motility disorders often produce adverse effects. A possible explanation for this is the presence of similar muscarinic receptor subtypes on smooth muscle from different gastrointestinal organs. The aim of this study was to characterize muscarinic receptor subtypes in human gastric smooth muscle with receptor binding methods. N-[3H]Methylscopolamine ([3H]NMS) saturation experiments showed a homogeneous population of noninteracting binding sites (KD = 0.76 ± 0.07 nM, Bmax = 46.94 ± 3.69 fmol/mg of tissue protein, nH = 0.99 ± 0.01). The rank order of inhibition of [3H]NMS binding by nonlabelled compounds was atropine [Formula: see text] otenzepad [Formula: see text] pirenzepine. Atropine and pirenzepine bound to a homogeneous population of binding sites. The inhibition of [3H]NMS binding by otenzepad showed two populations of receptors (nH < 1, p < 0.01), whose apparent Ki1of 298 ± 40 nM and apparent Ki2of 3.463 ± 0.62 mM were similar to those reported for the M2and M3muscarinic receptor subtypes. The M2subtype was the more abundant of the two, representing 79.12 ± 5.48% of the total population. We conclude that two muscarinic receptor subpopulations similar to the M2and M3subtypes are present in human gastric smooth muscle and that the M2-like receptor is the more abundant of the two.Key words: human stomach, muscarinic receptor subtypes, smooth muscle.
Publisher
Canadian Science Publishing
Subject
Physiology (medical),Pharmacology,General Medicine,Physiology
Cited by
6 articles.
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