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

Abstract

Eucalyptol is an essential oil that relaxes bronchial and vascular smooth muscle although its direct actions on isolated myocardium have not been reported. We investigated a putative negative inotropic effect of the oil on left ventricular papillary muscles from male Wistar rats weighing 250 to 300 g, as well as its effects on isometric force, rate of force development, time parameters, post-rest potentiation, positive inotropic interventions produced by Ca 2+ and isoproterenol, and on tetanic tension. The effects of 0.3 mM eucalyptol on myosin ATPase activity were also investigated. Eucalyptol (0.003 to 0.3 mM) reduced isometric tension, the rate of force development and time parameters. The oil reduced the force developed by steady-state contractions (50% at 0.3 mM) but did not alter sarcoplasmic reticulum function or post-rest contractions and produced a progressive increase in relative potentiation. Increased extracellular Ca 2+ concentration (0.62 to 5 mM) and isoproterenol (20 nM) administration counteracted the negative inotropic effects of the oil. The activity of the contractile machinery evaluated by tetanic force development was reduced by 30 to 50% but myosin ATPase activity was not affected by eucalyptol (0.3 mM), supporting the idea of a reduction of sarcolemmal Ca 2+ influx. The present results suggest that eucalyptol depresses force development, probably acting as a calcium channel blocker. Correspondence

Aerobic Exercise and Eucalyptus Globulus: Cardio-affective effects on recovery and stress

“…These findings suggest the important role played by the eucalyptol (1.8-cineole) in acute cardiovascular protection, in the face of stress condition in this system. Soares et al [8] showed that eucalyptol reduced cardiac inotropism in papillary muscles of rats, fact that can be directly related to SBP, HR and RPP in the current study. Dayawansa et al [22] demonstrated, via cedrol oil inhalation by humans, a reduced sympathetic nerve activity and an increased parasympathetic tone, thus presenting a consequent increase in the baroreflex sensitivity.…”

“…Eucalyptus globulus is an example of a species that shows special participation of the monoterpenic oxide 1.8-cineole [6]. Eucalyptol (1.8-cineole) has been presented as a cardiovascular system modulator acting on the cardiac inotropism of rats [7,8]. In addition to this, some regions of the central nervous system are activated when there is the inhalation of aromatic components derived from essential oils.…”

Chemical composition and mechanisms underlying the spasmolytic and bronchodilatory properties of the essential oil of Nepeta cataria L.

“…The presence of CCB constituent(s) was further evaluated by an indirect method when pretreatment of the tissues with Nc.Oil caused a rightward shift in the Ca ++ CRCs, similar to verapamil, a standard calcium channel blocker (Fleckenstein, 1977), which provides pharmacological basis for the medicinal use of the plant as antispasmodic and antidiarrheal as the CCBs are known to be useful in these conditions (Brunton, 1996). Interestingly, eucalyptol, an essential oil has also been reported to possess myorelaxant, vasodilator and cardiac suppressant activities partly through CCB mechanism (Soares et al, 2005).…”

Cardiovascular effects of monoterpenes: a review

“…Furthermore, Soares et al (2005) investigated eucalyptol effects on the papillary muscle preparations from rat ventricle. In these preparations, the eucalyptol produced a relaxation, possibly caused by inhibition of Ca 2+ influx through the membrane.…”