Doelman_1991_Eur.J.Pharmacol_193_117

Prejunctional inhibitory muscarinic receptors in guinea pig tracheal strips were investigated by electrical field stimulation. Pilocarpine and methacholine caused, in a similar way, a dose-dependent increase in baseline with a concomitant decrease in twitch response. We showed by using selective muscarinic antagonists, such as pirenzepine (M1-selective), methoctramine (M2-selective), AF-DX 116 (11-[[2-[diethylamino)methyl]-1-piperidinyl]-acetyl]-5,11-dihydro- 6H-pyrido[2,3-b] [1,4]benzodiazepine-6-one, M2-selective), gallamine (M2-selective) and 4-DAMP (4-diphenylacetoxy-N- methylpiperidinemethiodide, M3-selective), that the prejunctional inhibitory muscarinic receptor is of the M2 subtype.