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 dailyfor two weeks. For the next two weeks, these rats were divided intofour 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 ofcorticosterone and adrenocorticotropic hormone (ACTH) levels and hippocampus was dissected and stored in afreezer at -80 °C until assay for BDNF protein.
Results: BEO andfluoxetine 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 norfluoxetine had any effect on BDNF protein levels in hippocampus compared to their controls.
Conclusion: The inhalation ofBEO decrease behavior related depressive disorder similar tofluoxetine but has no effect on HPA axis response and BDNF protein levels in chronic restrained stress.