Howell_1991_Eur.J.Pharmacol_197_109

We examined the bronchodilator activity of eight subtype-selective and non-selective muscarinic antagonists in anesthetized, ventilated guinea pigs bronchoconstricted by carbachol aerosols. Relative bronchodilator potencies were consistent with M3 receptor antagonism and correlated with inhibition of bladder smooth muscle contraction in vivo. We conclude that the airway smooth muscle muscarinic receptor can be functionally characterized in vivo as M3 and that it is of the same subtype as the muscarinic receptor in bladder smooth muscle.