Fig. 3. ( A ) Effect of 4-diphenylacetoxyl-N -methylpiperidine methiodide (4-DAMP) on acetylcholine dose–response curve. 4-DAMP (10−9, 3 × 10−9, 10−8m) produced a parallel rightward shift (* P < 0.05 vs. no drug, † P < 0.05 vs. 10−9m 4-DAMP, ‡ P < 0.05 vs. 3 × 10−9m 4-DAMP) in the acetylcholine dose–response curve in a concentration-dependent manner. ( B ) A Schild plot was constructed with the concentration ratio (CR: ED50in the presence and absence of 4-DAMP) for individual experiments. The slope of the Schild plot for 4-DAMP was 0.942 ± 0.096 ( r 2= 0.856), and the concentration (− log M) of 4-DAMP necessary to displace the concentration–response curve of an acetylcholine by twofold was 9.256 ± 0.087. PE = phenylephrine.