Fig. 5. Antagonism of in vitro norepinephrine-induced contractions of proximal (A, D, G, and J) and distal (B, E, H, and K) rat CE duct segments. The effects of prazosin (A and B), RS 100329 (D and E), 5-methylurapidil (G and H), BMY 7378 (J and K), and L-765,314 (M and N) are presented. For clarity, in (J and K) only the effects of BMY 7378 (0.3–10 μM) are shown since the concentration-response curves for norepinephrine in the presence of BMY 7378 (10–100 nM) were superimposed to the control curves. The resulting Schild plots for the antagonism displayed by prazosin, RS 100329, 5-methylurapidil, and BMY 7378 are presented in (C, F, I, and L), respectively. Symbols represent the mean values and the vertical bars represent the S.E.M. values from four to six different segments taken from different rats.