Antidepressant-like Effects of Five Essential Oils Inhaled in Reserpine-induced Depressed Mouse Models

Depression, a prevalent and debilitating mood disorder, remains a significant challenge in clinical treatment. Although pharmacological approaches targeting monoamine dysfunction have demonstrated efficacy, they are often accompanied by limitations and side effects. In this study, reserpine-induced depressed mouse models were used to investigate the antidepressant potential of five essential oils (EOs) derived from Jasminum sambac (JSEOs), Rosa rugosa, Magnolia denudata, Aloysia citriodora (ACEOs), and Abies balsamea. The chemical compositions of the five EOs were analyzed using gas chromatography-mass spectrometry (GC-MS). Subsequently, experimental mice inhaled the EOs for 1 h per day, followed by behavioral assessments using the forced swim test (FST) and tail suspension test (TST). Nissl staining was employed to assess the abundance of normal neurons in the mouse brain. At the same time, immunohistochemistry (IHC), Western blot, and reverse transcription-quantitative polymerase chain reaction techniques were utilized to analyze the expression of antidepressant-related genes. GC-MS results revealed that the primary components of the five EOs were oxygenated monoterpenes, sesquiterpene hydrocarbons, and oxygenated sesquiterpenoids. All five EOs exhibited antidepressant-like effects, with JSEOs and ACEOs demonstrating the greatest antidepressant efficacy. Behavioral tests showed a reduction in immobility durations in both FST and TST. Nissl staining results indicated an increase in the number of intact neurons in the hippocampus and hypothalamus of mice following EO treatment. Furthermore, the EOs regulated the expression of crucial biomarkers, including 5-hydroxytryptamine 1A receptor (5-HT1A), 5-HT2A, brain-derived neurotrophic factor, corticotropin-releasing factor, and tropomyosin-related kinase B. This study underscores the potential of EO inhalation as an adjunctive therapeutic strategy for depression treatment, provides novel insights into its molecular mechanisms, and supports further exploration of natural remedies in mental health care.