title: Cardiovascular effects of 1,8-cineole, a terpenoid oxide present in many plant essential oils, in normotensive rats.
abstract: The cardiovascular effects of i.v. treatment with 1,8-cineole, a monoterpenic oxide present in many plant essential oils, were investigated in normotensive rats. This study examined (i) whether the autonomic nervous system is involved in the mediation of 1,8-cineole-induced changes in mean aortic pressure (MAP) and heart rate (HR) and (ii) whether the hypotensive effects of 1,8-cineole could result from its vasodilatory effects directly upon vascular smooth muscle. In both pentobarbital-anesthetized and conscious, freely moving rats, bolus injections of 1,8-cineole (0.3-10 mg/kg, i.v.) elicited similar and dose-dependent decreases in MAP. Concomitantly, 1,8-cineole significantly decreased HR only at the highest dose (10 mg/kg). Pretreatment of anesthetized rats with bilateral vagotomy significantly reduced the bradycardic responses to 1,8-cineole (10 mg/kg) without affecting hypotension. In conscious rats, i.v. pretreatment with methylatropine (1 mg/kg), atenolol (1.5 mg/kg), or hexamethonium (30 mg/kg) had no significant effects on the 1,8-cineole-induced hypotension, while bradycardic responses to 1,8-cineole (10 mg/kg) were significantly reduced by methylatropine. In rat isolated thoracic aorta preparations, 1,8-cineole (0.006-2.6 mM) induced a concentration-dependent reduction of the contraction induced by potassium (60 mM). This is the first physiological evidence that i.v. treatment with 1,8-cineole in either anesthetized or conscious rats elicits hypotension; this effect seems related to an active vascular relaxation rather than withdrawal of sympathetic tone.
authors.affiliation: Departamento de Fisiologia e Farmacologia, Centro de Ciências Biológicas, Universidade Federal de Pernambuco, 50670-901, Recife, PE, Brazil. lahlou@npd.ufpe.br
authors.forename: Saad
authors.initials: S
authors.lastname: Lahlou
authors.forename: André Fernandes
authors.initials: AF
authors.lastname: Figueiredo
authors.forename: Pedro Jorge Caldas
authors.initials: PJ
authors.lastname: Magalhães
authors.forename: José Henrique
authors.initials: JH
authors.lastname: Leal-Cardoso
mesh_terms: D000818:Animals; D001794:Blood Pressure / Q000187:drug effects / Q000502:physiology; D002319:Cardiovascular System / Q000187:drug effects*; D003511:Cyclohexanols / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D000077591:Eucalyptol; D008297:Male; D039821:Monoterpenes; D009822:Oils, Volatile / Q000494:pharmacology*; D010087:Oxides / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D013729:Terpenes / Q000494:pharmacology*; D014664:Vasodilation / Q000187:drug effects / Q000502:physiology
chemical_list: D003511:Cyclohexanols; D039821:Monoterpenes; D009822:Oils, Volatile; D010087:Oxides; D013729:Terpenes; D000077591:Eucalyptol