Cardiovascular effects of 1,8-cineole, a terpenoid oxide present in many plant essential oils, in normotensive rats

Abstract

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 concentrationdependent 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.Key words: 1,8-cineole, essential oil, cardiovascular effects, autonomic nervous system, isolated thoracic aorta.Résumé : On a examiné les effets d'un traitement par administration i.v. de 1,8-cinéole, un oxyde monoterpénique entrant dans le composition de nombreuses huiles essentielles, chez des rats normotendus. On a examiné (i) si le système nerveux autonome joue un rôle dans les variations induites par le 1,8-cinéole de la pression aortique moyenne (PAM) et de la fréquence cardiaque (FC) et (ii) si les effets hypotenseurs du 1,8-cinéole pourraient découler de ses effets vasodilatateurs directement sur le muscle lisse vasculaire. Des injections de bolus de 1,8-cinéole (0,3-10 mg/kg, i.v.) ont provoqué des diminutions similaires et dose dépendantes de la PAM chez les rats anesthésiés au pentobarbital et chez les rats conscients libres de circuler. Le 1,8-cinéole a aussi diminué significativement la FC mais à la dose la plus élevée uniquement (10 mg/kg). Chez les rats anesthésiés, un prétraitement au moyen d'une vagotomie bilatérale a réduit de manière significative les réponses bradycardiques au 1,8-cinéole (10 mg/kg) sans influer sur l'hypotension. Chez les rats conscients, un prétraitement i.v. de méthylatropine (1 mg/kg), d'aténolol (1,5 mg/kg) ou d'hexaméthonium (30 mg/kg) n'a pas eu d'effet significatif sur l'hypotension induite par le 1,8-cinéole, alors que les réponses bradycardiques au 1,8-cinéole (10 mg/kg) ont été significativemen...

Cardiovascular effects of monoterpenes: a review

“…Its cardiovascular effects were studied by Lahlou et al (2002), using a combined approach in vivo and in vitro. In this research, the authors demonstrated that intravenous administration of eucalyptol significantly reduced the blood pressure of both conscious and anesthetized rats.…”

“…This medicinal plant is popularly known as Colony and is widely used by the population as a tea in the treatment of arterial hypertension. Studies have shown that intravenous administration of α-terpinen-4-ol caused immediate blood pressure reduction in a dose-dependent manner in both normotensive (Lahlou et al, 2002) and hypertensive rats (Lahlou et al, 2003). In preparations of isolated rat aorta pre-contracted with depolarizing solution of K + , α-terpinen-4-ol was able to induce a concentrationdependent vasorelaxation (Lahlou et al, 2003).…”

Eucalyptol, an essential oil, reduces contractile activity in rat cardiac muscle

“…Cardiovascular effects were also recently reported. Lahlou et al (11) showed that eucalyptol reduced heart rate by a parasympathetic-dependent action and induced hypotension by a direct vasorelaxation.…”

Production of jet fuel precursor monoterpenoids from engineered Escherichia coli

“…1,8-cineole is used in non-prescription pharmaceuticals (e.g. cough suppressant, mouthwash), fragrances and flavoring agents (Lahlou et al, 2002) and can be used as additive to prevent separation in ethanol-gasoline fuel blends (Barton and Tjandra, 1989). Also, it has been shown that 1,8-cineole can be used for the synthesis of p-cymene (Leita et al, 2010;Leita et al, 2011), an important…”