Concentration-response curves to ACh in U-46619-contracted (0.3µM) second-order mesenteric arteries from (A, C) WKY and (B, D) SHRSP in the absence (closed symbols) or presence (open symbols) of (A, B) TRAM-34 (10µM) or (C, D) charybdotoxin (0.1µM). All the curves were performed in the presence of L-NAME (100µM) and indomethacin (10µM). Experimental values of the relaxation induced by ACh were calculated relative to the maximal changes from the contraction produced by U-46619 in each tissue. Results are presented as mean ± SEM of n=5 in each experimental group. *, P<0.05 compared with respective control (vehicle).