Effect of Inhaling bergamot oil on depression-related behaviors in chronic stressed rats

Abstract

Background: Bergamot essential oil (BEO) possesses sedation and anxiolytic properties similar to diazepam. After long period of exposure to stressors, including restrained stress, depressive-like behavior can be produced. BEO has been suggested to reduce depression. However, there is no scientific evidence supporting this property. Objective: To investigate the effect of BEO in chronic stressed rats on: 1) behavior related depressive disorder, 2) hypothalamic pituitary adrenal (HPA) axis response, and iii) brain-derived neurotrophic factor (BDNF) protein levels in hippocampus. Material and Method: Male Wistar rats, weighing 200 to 250 g, were induced chronic restrained stress 15 minutes daily for two weeks. For the next two weeks, these rats were divided into four groups, control-i.p., fluoxetine-i.p., control-inhale, and BEO-inhale. Fluoxetine (10 mg/kg i.p.) or saline was intraperitoneally administered daily while 2.5% BEO or saline was inhaled daily. At the end of the treatment, rats were assessed for depressive-like behavior using the forced swimming test (FST). After the behavioral test, the animals were immediately decapitated and trunk blood samples were collected for the measurement of corticosterone and adrenocorticotropic hormone (ACTH) levels and hippocampus was dissected and stored in a freezer at -80 °C until assay for BDNF protein. Results: BEO and fluoxetine significantly decreased the immobility time in the FST (p<0.05). Fluoxetine tended to decrease serum corticosterone and significantly (p<0.05) decreased serum ACTH while BEO had no effect on these two stress hormones. For BDNF protein determination, neither BEO nor fluoxetine had any effect on BDNF protein levels in hippocampus compared to their controls. Conclusion: The inhalation of BEO decrease behavior related depressive disorder similar to fluoxetine but has no effect on HPA axis response and BDNF protein levels in chronic restrained stress. © 2015, Medical Association of Thailand. All rights reserved.