Muscarinic M 3 receptors mediate contraction of human central and peripheral airway smooth muscle

Abstract

The muscarinic receptor subtype involved in human airway smooth muscle contraction was characterised for the first time, using subtype-selective muscarinic antagonists. It was demonstrated that methacholine-induced contraction of central (trachea) and peripheral (small bronchi) airway smooth muscle preparations was antagonised by pirenzepine, AF-DX 116, 4-DAMP methobromide, hexahydrosiladifenidol, and methoctramine with pA 2-values characteristic of M 3 (smooth muscle/glandular) muscarinic receptors. Since these pA 2-values demonstrate significant correlations with those found in bovine and guinea-pig tracheal smooth muscle contraction, it is concluded that these animal tissues provide a good model for the study of M 3 subtype-selective muscarinic antagonists to be used as bronchodilators.