Effects of Inhaled Lavender Essential Oil on Stress-Loaded Animals: Changes in Anxiety-Related Behavior and Expression Levels of Selected mRNAs and Proteins

Abstract

Inhalation of various essential oils elicits behavioral changes as a consequence of a complex centrally coordinated response. To understand the molecular mechanisms of action of aromatic compounds on emotional responses, we evaluated the stress-induced changes in mouse brain and the efficacy of inhaled essential oil from Lavandula officinalis (LvEO) using two approaches: a behavioral test, and examining the expression levels of selected genes {fast nerve growth factor receptor (NGFR) mRNA, activity regulated cytoskeletal-associated protein (Arc) mRNA} and proteins {galactokinase 1 (GLK1) and brain-derived neurotrophic factor (BDNF)}. Animals were randomly divided into 4 groups depending on the treatment given: stress (-)/H2O, stress (-)/LvEO, stress (+)/H2O, and stress (+)/LvEO group. For behavioral testing, using an elevated plus-maze test, significant anxiolytic-like effects were seen in both the stress (-)/LvEO and stress (+)/LvEO groups, indicating that LvEO exerts anxiolytic-like effects regardless of the administration of water immersion stress. On expression analysis, the levels of NGFR and Arc mRNA were significantly lower in animals subjected to stress. Inhalation of LvEO, however, reversed this change, thus suggesting that LvEO negates the impact of stress on gene expression levels. Meanwhile, significant decreases in expression levels were also observed in the stress (-)/LvEO group, which implies that LvEO, when given in a stress-free situation, may act as a stress stimulus. Taken together, our data suggest that inhalation of LvEO exerts bidirectional influences in the central nervous system (CNS) of animals, either attenuating the effects of stress or acting as a stressor, depending on the subject state.