Effect of Inhaling Bergamot Oil on Depression-Related Behaviors in Chronic Stressed Rats
Somrudee Saiyudthong PhD*, Chantana Mekseepralard PhD**
Affiliation : * Department of Physiology, Faculty of Medicine, Srinakharinwirot University, Bangkok, Thailand ** Department of Microbiology, Faculty of Medicine, Srinakharinwirot University, Bangkok, Thailand
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 oC 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.
Keywords : Depression, Bergamot oil, Force swimming test, HPA axis, BDNF
