Fig. 7. Tension recordings showing the vasodilatory effect of nicotine on the crocodile right aorta with the endothelium intact (A) and with the endothelium removed (B). Haematoxylin and Eosin staining was used to verify that the endothelium was present or removed (see inset). The preparations were exposed to ET-1 (10^-8 mol l^-1) until a maximum constriction was achieved and then nicotine (3x10^-4 mol l^-1) was added. Nicotine induced a vasodilation in both preparations. The lower graph shows the mean response of nicotine on pre-constricted right and dorsal aortae with the endothelium intact (filled bars) or the endothelium removed (open bars). There is no significant difference in the nicotine-mediated vasodilation with or without the endothelium (right aorta, P=0.52, dorsal aorta, P=0.63, N=5).