Authors: Somrudee Saiyudthong, Sirinun Pongmayteegul, Udomsri Showpittapornchai, Pansiri Phansuwan-Pujito
A pilot study has shown that vetiver essential oil (VEO) possesses anxiolytic properties similar to diazepam, a widely used anxiolytic drug. A variety of stressors, including restrain, can produce anxiety-like behaviour. The aim of this present study was to investigate the effects of VEO on restrained stressinduced anxiety-related behaviour, plasma corticosterone and c-fos expression in amygdala and hypothalamus. Male Wistar rats were divided into 4 groups, CONT+homecage, CONT+restrained stress, VEO+homecage, VEO+restrained stress. Rats were inhaled with 2.5%VEO or saline for 7 min, and then exposed to restrained stress or leaved in home cage for 15 min prior to exposure to the elevated plus maze (EPM). At the end of the experiment, the animals were immediately decapitated and trunk blood samples were taken for the corticosterone enzymeimmunoassay. Restrained stress enhanced anxiety-like behaviour in the EPM and serum corticosterone but 2.5%VEO did not attenuate these stress-induced changes. VEO tended to increase c-fos expression in entire amygdala regions but the significant increase was observed only the central amygdaloid nucleus (CeA) where similar to those observed with restrained stress. Moreover, restrain stress increased c-fos expression in paraventricular nucleus of the hypothalamus whereas VEO had no effects on either control or stress condition. These findings suggest that VEO has anxiety-like behaviour in normal condition involving activation of CeA. The activation of the hypothalamic-pituitaryadrenal axis induced by restrain stress could not be attenuated by VEO inhalation.
Keywords: essential oil, elevated plus maze, HPA axis, hypothalamus, amygdala, stress