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The vasodilator effect of the ethanolic extract of leaves from Hancornia speciosa Gomes (HSE) was evaluated in superior mesenteric artery rings. HSE produced a concentration-dependent vasodilation (IC₅₀=10.8±4.0μg/mL) in arterial rings pre-contracted with phenylephrine, which was completely abolished in endothelium-denuded vessels. Endothelium-dependent vasodilation induced by HSE was strongly reduced by l-NAME (100μM), a nitric oxide (NO) synthase inhibitor, but neither by atropine, a muscarinic receptor antagonist (1μM), nor by indomethacin (10μM), a cyclooxygenase inhibitor. In rings pre-contracted with 80mM KCl, the vasodilator effect of HSE was shifted to the right and was completely abolished in the presence of l-NAME (100μM). Similar effects were obtained in mesenteric rings pre-contracted with phenylephrine in the presence of KCl 25mM alone or in addition to 100μM l-NAME. In addition …