Cardiovascular effects of Sida cordifolia leaves extract in rats

The cardiovascular activity of the aqueous fraction of the hydroalcoholic extract of Sida cordifolia leaves (AFSC) was evaluated. In normotensive non-anaesthetized rats was observed that AFSC (5, 10, 20, 30 and 40 mg/kg, i.v.) induced hypotension (6 ± 2%; 8 ± 2%; 11 ± 2%; 19 ± 3% and 33 ± 3%, respectively) and bradycardia (0.3 ± 3%; 13 ± 4%; 38 ± 6%; 64 ± 7% and 80 ± 5%, respectively). Hypotensive response was completely abolished after atropine (2 mg/kg; i.v.) but potentialized after hexamethonium (20 mg/kg; i.v.) (12 ± 2%; 21 ± 5%; 28 ± 3%; 32 ± 2% and 32 ± 3%, respectively), while bradycardic response was completely abolished after atropine (2 mg/kg; i.v.) and attenuated with hexamethonium (20 mg/kg; i.v.) (1 ± 0.3%; 5 ± 1%; 7 ± 1%; 7 ± 1% and 10 ± 1%, respectively). In hexamethonium treated rats, l-NAME significantly attenuated the hypotensive response (9 ± 2%; 14 ± 1%; 16 ± 1%; 16 ± 2% and 22 ± 3%, respectively). In normotensive anaesthetized and vagotomized rats, hypotensive and bradycardic responses were significantly attenuated (0.5 ± 0.2%; 1 ± 0.4%; 3 ± 0.6%; 4 ± 0.8% and 6 ± 1%, respectively, n = 6, and 7 ± 2%; 12 ± 5%; 15 ± 2%, 17 ± 2% and 25 ± 3%, respectively). The anaesthesia with sodium thiopental did not affect the AFSC-induced responses when compared with those induced in non-anaesthetized rats (data not showed). In conclusion, the results obtained so far show that AFSC produce hypotension and bradycardia, mainly due to a direct stimulation of the endothelial vascular muscarinic receptor and indirect cardiac muscarinic activation, respectively.