Cardiovascular effects of the essential oil of Croton zehntneri leaves and its main constituents, anethole and estragole, in normotensive conscious rats.
Cardiovascular effects of the essential oil of Croton zehntneri (EOCZ) were investigated in conscious rats. In these preparations, intravenous (i.v.) injections of EOCZ (1-20 mg kg(-1)) and its main constituents anethole and estragole (both at 1-10 mg kg(-1)) elicited brief and dose-dependent hypotension and bradycardia (phase I) that were followed by a significant pressor effect associated with a delayed bradycardia (phase II). The initial hypotension and bradycardia (phase I) of EOCZ were unchanged by atenolol (1.5 mg kg(-1), i.v.) or L-NAME (20 mg kg(-1), i.v.) pretreatment, but were respectively reversed into pressor and tachycardic effects by methylatropine (1 mg kg(-1), i.v.) pretreatment. The subsequent pressor effect and the delayed bradycardia (phase II) remained unaffected by atenolol, but were abolished by L-NAME and methylatropine pretreatment, respectively. In rat endothelium-containing aorta preparations, the vasoconstrictor responses to phenylephrine were enhanced and reduced, respectively, by the lower (1-30 microg mL(-1)) and higher (300-1000 microg mL(-1)) concentrations of EOCZ. Only the enhancement of phenylephrine-induced contraction was abolished by either the incubation with L-NAME (50 microM) or in the absence of the endothelium. These data show, for the first time, that i.v. administration EOCZ induces an initial hypotension followed by a pressor response, two effects that appear mainly attributed to the actions of anethole and estragole. The EOCZ-induced hypotension (phase I) is mediated by a cholinergic mechanism and seems to result mainly from the concomitant bradycardia. The pressor response of EOCZ (phase II) seems to be caused by an indirect vasoconstrictive action of EOCZ most likely through inhibition of endothelial nitric oxide production.
de Siqueira
Rodrigo José Bezerra
RJ
Department of Physiology and Pharmacology, Center of Biological Sciences, Federal University of Pernambuco, 50670-901, Recife, Pernambuco, PE, Brazil.
Magalhães
Pedro Jorge Caldas
PJ
Leal-Cardoso
José Henrique
JH
Duarte
Gloria Pinto
GP
Lahlou
Saad
S
D000081248:Allylbenzene Derivatives; D000818:Animals; D000840:Anisoles / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D001013:Aorta, Thoracic / Q000187:drug effects; D001794:Blood Pressure / Q000187:drug effects; D003436:Croton Oil / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D004730:Endothelium, Vascular / Q000187:drug effects; D006339:Heart Rate / Q000187:drug effects; D006439:Hemodynamics / Q000187:drug effects*; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000187:drug effects; D009569:Nitric Oxide / Q000378:metabolism; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors; D018515:Plant Leaves / Q000737:chemistry; D051381:Rats; D017208:Rats, Wistar; D014664:Vasodilation / Q000187:drug effects
D000081248:Allylbenzene Derivatives; D000840:Anisoles; D009569:Nitric Oxide; D003436:Croton Oil; C007633:estragole; D019001:Nitric Oxide Synthase; C006578:anethole