Fig. 5. Tension recordings showing the vasodilatory effect of acetylcholine (ACh) on the lateral aorta with the endothelium removed (A) and with the endothelium intact (A). The preparations were exposed to endothelin-1 (ET-1; 10^-8 mol l^-1) until a maximum constriction was achieved and then ACh (10^-5 mol l^-1) was added. (C) Mean response (% vasodilation) of ACh on pre-constricted lateral and dorsal aortae with the endothelium removed (filled bars) or the endothelium intact (open bars). Note that there is no significant difference in the ACh-mediated dilation (lateral aortae, P=0.26; dorsal aorta, P=0.35; N=5).