RESUMEN
The cardiovascular effects induced by the aqueous fraction of the ethanol extract of the stem (AFS) of Solanum stipulaceum Roem. & Schult were studied in rats. In non-anesthetized rats, AFS injections produced significant and dosedependent hypotension associated with increase in heart rate. In isolated rat superior mesenteric rings, AFS was able to antagonize the contractions induced by phenylephrine and KCl. The vasorelaxant activity of AFS was not inhibited by either removal of vascular endothelium, L-NAME, atropine or indomethacine. In isolated rat atrial preparations, AFS produced concentration-related negative inotropic and chronotropic responses. These results suggest that the hypotensive effect of AFS is due to a peripheral vasodilation, which can not be attributed to the participation of vascular endothelium. Finally, AFS acts directly on the heart decreasing contractility and heart rate.