Cardiodepression as a possible mechanism of the hypotensive effects of the methylene chloride/methanol leaf extract of Brillantaisia nitens Lindau (Acanthaceae) in rats
Brillantaisia nitens Lindau (Acanthaceae) is traditionally used in Cameroon for the management of many diseases including cardiovascular disorders. The aim of this study was to demonstrate the contribution of cardiodepressive activity of methylene chloride/methanol leaf extract of B. nitens to its hypotensive action in normotensive (NTR) and deoxycorticosterone acetate-salt hypertensive rats (DSHR). In this study, we used the direct cannulation method for blood pressure measurements and electrodes for electrocardiogram (ECG). In NTR, the systolic blood pressure dropped by 12.6, 13.8, 22.5 and 39.3% at the doses 5, 10, 20 and 40 mg/kg, respectively. In DSHR, systolic blood pressure decreased by 13.8, 16.2, 16.3 and 20.4% at the same doses, respectively. B. nitens extract (40 mg/kg) produced a significant reduction of the heart activity while the blood pressure rapidly dropped. At this same dose in NTR, B. nitens induced a negative chronotropic effect by causing a 20.59% (p<0.05) R-R interval elongation. More also, On P wave and T wave magnitude, the plant extract at the same dose induced a significant (p<0.05) decrease of 21.05 and 15.79%, respectively. For DSHR, B. nitens extract (40 mg/kg) induced significant changes on T wave duration, R-R interval and P wave magnitude. B. nitens extract decreased T wave duration by 44.44% (p<0.05), increased R-R interval by 100% (p<0.01) and decreased P wave magnitude by 20% (p<0.05). These results confirm our previous findings that the immediate hypotensive effect of B. nitens is partly due to its depressive effect on the cardiac pump.
Key words: Brillantaisia nitens, methylene chloride/methanol extract, hypotensive effect, cardiodepressive activity, rat.