Research on the Improvement Effects and Mechanisms of Magnolia sieboldii Essential Oils on Insomnia in Mice

(1) Background: Insomnia is a common sleep disorder that is difficult to cure due to its long duration of influence. Magnolia sieboldii essential oils (MSEOs) have been shown to have antidepressant effects, but there are few studies on treating insomnia. Therefore, this study aimed to investigate the therapeutic effects of MSEOs and to elucidate the molecular and neurophysiological mechanisms by which they alleviate insomnia. (2) Methods: The main components of MSEOs extracted by steam distillation were analyzed by gas chromatography-mass spectrometry (GC-MS). To establish a p-chlorophenylalanine (PCPA) -induced insomnia model in mice, the levels of GAD65, GABAARα1, 5HT-2A, and 5HT-1A were detected by immunohistochemistry and ELISA. The normal neurons in the mouse brain were counted by Nissl staining. The relative mRNA expression levels of related genes in mice were detected by RT- qPCR. (3) Results: A total of 69 components were identified by MSEOs, and the main components were β-elemene (19.94%), (Z)-β-ocimene (14.87%), and Germacrene D (7.05%). Both low and high concentrations of MSEOs can successfully prolong the total sleep time and shorten the sleep latency of mice. GAD65, GABAARα1, 5HT-2A, and 5HT-1A levels still increased to varying degrees after treatment with different concentrations of MSEOs. The results of Nissl staining showed that MSEOs could attenuate PCPA-induced neuronal death. The RT- qPCR results showed that MSEOs enhanced the mRNA expression of 5HT-2A, GABAARα1, and GABAARγ2. (4) Conclusions: MSEOs effectively improved sleep by prolonging total sleep time and shortening latency, potentially through upregulating GAD65, GABAARα1, 5HT-1A, and 5HT-2A levels, protecting neurons, and enhancing mRNA expression of GABAARα1, GABAARγ2, and 5HT-2A, suggesting their potential as a therapeutic for insomnia.