Abstract
β-Citronellol is an alcoholic monoterpene found in essential oils such Cymbopogon citratus (a plant with antihypertensive properties). β-Citronellol can act against pathogenic microorganisms that affect airways and, in virtue of the popular use of β-citronellol-enriched essential oils in aromatherapy, we assessed its pharmacologic effects on the contractility of rat trachea. Contractions of isolated tracheal rings were recorded isometrically through a force transducer connected to a data-acquisition device. β-Citronellol relaxed sustained contractions induced by acetylcholine or high extracellular potassium, but half-maximal inhibitory concentrations (IC50) for K+-elicited stimuli were smaller than those for cholinergic contractions. It also inhibited contractions induced by electrical field stimulation or sodium orthovanadate with pharmacologic potency equivalent to that seen against acetylcholine-induced contractions. When contractions were evoked by selective recruitment of Ca2+ from the extracellular medium, β-citronellol preferentially inhibited contractions that involved voltage-operated (but not receptor-operated) pathways. β-Citronellol (but not verapamil) inhibited contractions induced by restoration of external Ca2+ levels after depleting internal Ca2+ stores with the concomitant presence of thapsigargin and recurrent challenge with acetylcholine. Treatment of tracheal rings with L-NAME, indomethacin or tetraethylammonium did not change the relaxing effects of β-citronellol. Inhibition of transient receptor potential vanilloid subtype 1 (TRPV1) or transient receptor potential ankyrin 1 (TRPA1) receptors with selective antagonists caused no change in the effects of β-citronellol. In conclusion, β-citronellol exerted inhibitory effects on rat tracheal rings, with predominant effects on contractions that recruit Ca2+ inflow towards the cytosol by voltage-gated pathways, whereas it appears less active against contractions elicited by receptor-operated Ca2+ channels.
Highlights
The acyclic monoterpenoid b-citronellol (3,7-dimethyl-6octen-1-ol; CAS number 106-22-9) has odor qualities that make it useful in the perfume industry [1]
Antagonism of transmembrane calcium ion (Ca2+) influx from the extracellular medium as well as inhibition of release of intracellular Ca2+ from Ca2+ stores appear to mediate its inhibitory effects on vascular smooth muscle [9]
Though significant at higher concentrations, our findings argue against putative involvement of the vehicle in the relaxant effects induced by b-citronellol on rat tracheal rings
Summary
The acyclic monoterpenoid b-citronellol (3,7-dimethyl-6octen-1-ol; CAS number 106-22-9) has odor qualities that make it useful in the perfume industry [1]. Tracheal rings were challenged to contract in response to contractile stimuli (in general, a high potassium ion (K+) concentration (60 mM) or acetylcholine (ACh; 5 mM)).
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