Cardiovascular effects of methyleugenol, a natural constituent of many plant essential oils, in normotensive rats.
Cardiovascular effects of intravenous (i.v.) treatment with methyleugenol (ME), a natural constituent of many plant essential oils, were investigated in normotensive rats. Additionally this study examined (I) whether the autonomic nervous system is involved in the mediation of ME-induced changes in mean aortic pressure (MAP) and heart rate (HR), and (II) whether the hypotensive effects of ME could result from its vasodilatory effects directly upon vascular smooth muscle. In both pentobarbital-anesthetized and conscious rats, i.v. bolus injections of ME (1 to 10 mg/kg) elicited similar and dose-dependent decreases in MAP. In anesthetized rats, ME decreased HR only at the highest dose (10 mg/kg), while changes of this parameter were not uniform in conscious rats. Pretreatment of anesthetized rats with bilateral vagotomy significantly reduced the bradycardia response to ME (10 mg/kg) without affecting the hypotension. In conscious rats, i.v. pretreatment with methylatropine (1 mg/kg) or hexamethonium (30 mg/kg) had no significant effect on ME-induced hypotension. In rat isolated thoracic aorta preparations, ME (0.006-1.68 mM) induced a concentration-dependent reduction of potassium (60 mM)-induced contraction. This is the first physiological evidence that i.v. treatment with ME in either anesthetized or conscious rats elicits hypotension; an effect that seems related to an active vascular relaxation rather than withdrawal of sympathetic tone.
Departamento de Fisiologia e Farmacologia, Centro de Ciências Biológicas, Universidade Federal de Pernambuco, Avenida Prof. Moraes Rego, 50670-901, Recife, PE, Brazil. lahlou@ufpe.br
Saad
S
Lahlou
André Fernandes
AF
Figueiredo
Pedro Jorge Caldas
PJ
Magalhães
José Henrique
JH
Leal-Cardoso
Pinto Duarte
PD
Gloria
D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D000959:Antihypertensive Agents / Q000494:pharmacology; D001011:Aorta / Q000187:drug effects / Q000378:metabolism; D001286:Atropine Derivatives / Q000494:pharmacology; D001794:Blood Pressure / Q000187:drug effects*; D002319:Cardiovascular System / Q000187:drug effects*; D005054:Eugenol / Q000031:analogs & derivatives* / Q000494:pharmacology*; D006339:Heart Rate / Q000187:drug effects; D018738:Hexamethonium / Q000494:pharmacology; D066298:In Vitro Techniques; D008297:Male; D015394:Molecular Structure; D010936:Plant Extracts / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D014661:Vasoconstriction / Q000187:drug effects; D014664:Vasodilation / Q000187:drug effects; D014665:Vasodilator Agents / Q000494:pharmacology; D014700:Verapamil / Q000494:pharmacology
D000959:Antihypertensive Agents; D001286:Atropine Derivatives; D010936:Plant Extracts; D014665:Vasodilator Agents; C005223:methyleugenol; D018738:Hexamethonium; D005054:Eugenol; C006649:methylatropine; D014700:Verapamil; D000109:Acetylcholine