Evaluation of the cardiovascular effects of vasicine, an alkaloid isolated from the leaves of Sida cordifolia L. (Malvaceae)

The cardiovascular effects of vasicine, an alkaloid isolated from the leaves of Sida cordifolia L., were evaluated in this work. In non-anaesthetized rats (n=6), vasicine (1, 2.5, 5 and 10 mg/kg; i.v., randomly) induced hypotension associated with an intense bradycardia. Both responses were completely abolished after atropine (2mg/Kg; i.v.) and attenuated after hexamethonium (20 mg/Kg; i.v.). In isolated rat mesenteric artery rings, vasicine (0.03, 0.1, 0.3, 1, 3, 10, 30, 100 and 300 μg/mL, cumulatively) induced concentration-dependent relaxation of phenylephrine-induced tone (IC50= 3.8±0.9 μg/mL; n = 6). In conclusion, the results show that vasicine produce hypotension and bradycardia which appears to be due to the stimulation of cardiac muscarinic receptors (directly and/or indirectly), and by a decrease of the peripheral resistances