Mechanisms of the contractile effect of the hydroalcoholic extract of Cissampelos sympodialis Eichl. in the rat aorta.
In the present work the effect of the aqueous fraction of the ethanolic extract of the leaves (AFL) of Cissampelos sympodialis Eichl. was investigated in the rat aorta. In the presence of functional endothelium, AFL produced concentration-dependent contractions (EC50 value of 76.6 +/- 17.8 micrograms/ml). In the absence of functional endothelium, the concentration-response curves to AFL were significantly shifted to the left (EC50 values of 1.3 +/- 0.9 micrograms/ml) without modification of its maximal contractile effect. In the presence of L-NAME (300 microM) and of indomethacin (10 mM), the concentration-response curves produced by AFL were also shifted to the left (EC50 values of 21.8 +/- 6.2 and 24.3 +/- 13.2 micrograms/ml, respectively). The treatment of the aortas with L-NAME (300 microM) plus indomethacin (10 microM) produced a significant shift to the left of the concentration-dependent curves of AFL (EC50 value of 4.9 +/- 2.2 micrograms/ml), similar to that observed in the absence of the vascular endothelium. In addition, AFL-induced contraction was abolished in the presence of prazosin (1 microM), and significantly shifted to the right in the presence of yohimbine (EC50 value of 723.6 +/- 76.4 micrograms/ml). Thus, based on these results, it can be concluded that contractions induced by AFL in the rat aorta were due to activation of alpha-adrenoceptors. Furthermore, these results also showed that the AFL-induced contractions were modulated by the endothelium, via the release of NO and of a cyclooxygenase-derived relaxant product. Finally, it can be concluded that the contractile effects of AFL on vascular smooth muscle may play an important role in the hypertensive effects of this plant in vivo.
Freitas
M R
MR
Laboratório de Tecnologia Farmacêutica, Universidade Federal da Paraíba, Joao Pessoa-PB, Brazil.
Lemos
V S
VS
Queiroga
C E
CE
Thomas
G
G
Medeiros
I A
IA
Côrtes
S F
SF
D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology; D000438:Alcohols / Q000737:chemistry; D000818:Animals; D001011:Aorta / Q000187:drug effects*; D016861:Cyclooxygenase Inhibitors / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology; D007213:Indomethacin / Q000494:pharmacology; D019684:Magnoliopsida / Q000737:chemistry*; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects*; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009569:Nitric Oxide / Q000378:metabolism; D010936:Plant Extracts / Q000494:pharmacology; D018515:Plant Leaves / Q000737:chemistry; D010946:Plants, Medicinal / Q000737:chemistry*; D011451:Prostaglandin-Endoperoxide Synthases / Q000187:drug effects; D051381:Rats; D017208:Rats, Wistar; D011942:Receptors, Adrenergic, alpha / Q000187:drug effects
D000317:Adrenergic alpha-Antagonists; D000438:Alcohols; D016861:Cyclooxygenase Inhibitors; D004791:Enzyme Inhibitors; D010936:Plant Extracts; D011942:Receptors, Adrenergic, alpha; D009569:Nitric Oxide; D011451:Prostaglandin-Endoperoxide Synthases; D019331:NG-Nitroarginine Methyl Ester; D007213:Indomethacin