Cardiovascular effects of an aqueous fraction of the ethanol extract of the leaves of Cissampelos Eichl. in the rat.

The cardiovascular effects of the aqueous fraction of the ethanol extract of the leaves (AFL) of Cissampelos sympodialis Eichl. were evaluated in this work. In conscious freely moving rats, AFL (0.5, 1, 2, 4 and 8 mg/kg, i.v.) increased the mean arterial pressure (MAP) by 7 ± 2,16 ± 5, 33 ± 5, 43 ± 3 and 38 ± 4 mmHg, respectively, followed by a significant decrease in heart rate. After cardiac autonomic blockade (atenolol + atropine, 2 mg/kg, i.v., each), the hypertensive effects produced by AFL (2 and 4 mg/kg) were potentiated. However, AFL was ineffective in producing bradycardia. In anesthetized rats, AFL (4 mg/kg) induced similar increases in MAP (34 ± 4 mmHg) and bradycardia (-160 ± 24 bpm). Further, it induced a third-degree atrioventricular (AV) blockade. Nevertheless, both bradycardia and AV-blockade were completely abolished after atropine. While the AFL failed to induce bradycardia directly in the isolated perfused rat heart, in isolated right and left rat atria, it produced positive chronotropic and inotropic effects. The results demonstrate that the AFL markedly increases blood pressure in conscious unrestrained and anesthetized rats and improves heart rate and contractility in isolated perfused atrial preparations. Furthermore, the results suggest that the bradycardia associated with increase in blood pressure is reflex in origin.