Antidepressant Effect and Mechanism of Picea mariana Essential Oil on Reserpine-Induced Depression Model Mice.

The disturbance of brain biochemical substances serves as a primary cause and aggravating factor of depression. This study aimed to investigate the principal components of Picea mariana and its effect on reserpine-induced depression mice,w ith its relationship with brain central transmitters and related proteins. The main constituents of P. mariana essential oil (PMEO) were analyzed by GC-MS spectrometry. The quiescent time in the tail suspension test (TST) and forced swim test (FST), along with the weight change of the mice was detected. The number of normal neurons was quantified through Nissl staining. Immunohistochemistry was employed to determine the levels of 5HT-_1A and 5HT-_2A in the brain. Western blotting was utilized to detect 5HT-_2A, CRF and TrkB protein levels. RT-qPCR was used to detect the mRNA levels of 5HT-_1A, 5HT-_2A, TrkB, CRF, and BDNF. The main active ingredients of PMEOs were (-) -bornyl acetate (44.95%), γ-Terpinene (14.17%), and β-Pinene (10.12%). PMEOs effectively improved the retardation and weight loss due to anorexia in depression-like mice. This improvement was associated with an increase in the number of normal neurons. After administering different doses of PMEOs, the levels of 5HT-_1A, 5HT-_2A, CRF, and TrkB were found to be increased in brain tissue. RT-qPCR revealed that the mRNA levels of CRF, 5HT-_1A, and 5HT-_2A were generally upregulated, whereas TrkB and BDNF were downregulated. PMEO can effectively alleviate depression induced by reserpine, which may be attributed to its regulation of 5HT-_1A, 5HT-_2A, CRF and TrkB protein expression, thus reducing brain nerve injury.