Figure 2.

Selectivity of EP receptor antagonists: cumulative inhibition curves for (A) SC-51322 (B) (ONO)-5-methyl-1 (C) AH-6809 and (D) (DG)-3ap on guinea-pig trachea and aorta. Contraction was established with 17-phenyl PGE₂, U-46619 and carbachol on trachea and 17-phenyl PGE₂ primed with phenylephrine (net EP₃ response = 100%) on aorta. The inset in panel C shows the effect of 10 µM AH-6809 against phenylephrine (2 µM, PE), histamine (1.5 µM, H) and U-46619 (20–30 nM, U) on guinea-pig aorta; inhibition with 1 µM AH-6809 was <5% in each case. BMS-180291 (1 µM) was present for all 17-phenyl PGE₂ tests. Error bars indicate s.e.mean (n = 4). Carbachol activates M₃ receptors in guinea-pig trachea (Morrison and Vanhoutte, 1992).