Concentration-response curves for ACh in isolated tracheal preparations of guinea-pigs in the absence (◊) and in the presence (▲) of atropine (0.25 mg/ml; 3A), and pre-treatment (Δ) with Edici at a single concentration of 10 mg/ml (3A). Concentration of ACh are expressed as the log10 of the molar concentration. Each Point represents the mean values obtained using 6 rings. Each obtained from different animal. Brackets indicate SEM (n = 4-6).