Possible mechanisms of action of the neutral extract from Bidens pilosa L. leaves on the cardiovascular system of anaesthetized rats

Abstract

The aim of this study was to investigate the hypotensive and cardiac effects of the neutral extract from Bidens pilosa leaves. Intravenous administration of the extract resulted in a biphasic dose-related hypotensive activity. In normotensive rats (NTR), B. pilosa decreased systolic blood pressure by 18.26%, 42.5% and 30% at doses of 10, 20 and 30 mg/kg, respectively. In spontaneously hypertensive rats (SHR), the decrease in systolic blood pressure was 25.77%, 38.96% and 28.64% at the above doses, respectively. These doses induced hypotension by 27%, 34.13% and 18.73% respectively in salt-loaded hypertensive rats. In NTR, B. pilosa reduced heart rate by 23.68% and 61.18% at doses of 20 and 30 mg/kg, respectively. The force of contraction of the heart was only affected at 30 mg/kg. The initial phase of hypotensive response was partially inhibited by atropine while propranolol increased this effect. These results suggest that B. pilosa exhibited its fi rst hypotensive effects by acting on the cardiac pump efficiency and secondly through vasodilation.

Effect of Tulbaghia violacea on the blood pressure and heart rate in male spontaneously hypertensive Wistar rats

“…Muscarine (2.5 µg/kg) was then infused into the same animal, after the BP and HR returned to the level prior to the infusion of the MLE. The drugs were infused 20 minutes after atropine infusion (Thán et al, 2000;Dimo et al, 2003;Dabire, 2004;Adami et al, 2006;Ajay et al, 2007; D. Holopherne et al, 2008;Khwanchuea et al, 2008;Lessa et al, 2008;Rattmann et al, 2008;De Menezes et al, 2010).…”

“…MAP (mmHg) In this study, propranolol was used as a positive control for the possible effect of the MLE on the β 1 adrenoceptors, although propranolol is a non selective β adrenoceptor blocker which acts on both beta 1(β 1 ) and beta 2 (β 2 ) receptors (Dimo et al, 2003;Lin et al, 2007;Weir, 2009). In a dose-dependent manner, propranolol (0.1 -3.2 mg/kg) reduced (a) the SBP from 189.7 ± 3.3 mmHg observed at baseline, to 179.6 ± 4.8 mmHg, i.e., by 1.2 ± 0.6% (maximum effect of lowest dose), and to 134.3 ± 7.6 mmHg, i.e., by 29.2 ± 3.5% (maximum effect of highest dose); (b) the DBP from 143.6 ± 4.5 mmHg observed at baseline, to 143.0 ± 5.3 mmHg, i.e., by 0.4 ± 0.8% (maximum effect of lowest dose), and to 90.0 ± 9.5 mmHg, i.e., by 37.3 ± 5.9% (maximum effect of highest dose); (c) the MAP from 159.1 ± 3.9 mmHg at baseline, to 158.2 ± 4.7 mmHg, i.e., by 0.6 ± 0.7 % (maximum effect of lowest dose), and to 104.9 ± 8.3 mmHg, i.e., by 34.1 ± 4.7% (maximum effect of highest dose) (figure 4.37 a);…”

“…The faster heart beats, the less likely the heart muscle are able to sufficiently relax prior to the next systole, therefore, the DBP will rise (Bell, 2008) In a related experiment, propranolol was used as a positive control used to compare the effect of the MLE on the effect of β 1 adrenoceptors. Propranolol is a non selective β adrenoceptor blocker, with actions on both the β 1 and β 2 receptors (Dimo et al, 2003;Lin et al, 2007;Weir, 2009). In a dose-dependent manner, propranolol (0.1 -3.2 mg/kg) reduced the SBP, DBP, MAP and HR; but had no effect on the PP (figures 4.36 and 4.37).…”

“…The prominent BP profile and magnitude was that of atropine ( figure 4.44 a). Infusion of agonists was done 20 minutes after infusing atropine in most studies in which atropine was used to block the muscarinic receptors (Muntzel et al, 1997;Dimo et al, 2003;Delphine Holopherne et al, 2008;Khwanchuea et al, 2008;Lessa et al, 2008;Liu et al, 2008;Rattmann et al, 2008;Shirasaka et al, 2009;De Menezes et al, 2010). violacea were significantly (p < 0.05) higher than those observed with muscarine after pretreatment of animals with atropine.…”

Phytochemical Screening, Acute Toxicity and Cardiovascular Effects of Water Extract of Hallea Ledermannii (K. Krause) Verdc (Rubiaceae), Medicinal Plant From Gabon.

“…Evaluation of cardiovascular effects:-Anesthesia of the animal and catheterization of the femoral vein and the carotid artery:-The general anesthesia of the rats was carried out by intra-peritoneal injection of urethane 15 % at 1.5g/kg at the rate of 1 mL/100 g of rat body weight (Dimo et al, 2003). The anesthetized animal was fixed in dorsal decubitus, by means of pins planted on these legs on a cork board.…”