Sedative and Hypnotic Effects and Transcriptome Analysis of Polygala tenuifolia in Aged Insomnia Rats

Polygala tenuifolia has been commonly used as a sedative-hypnotic herb in China from ancient time to nowadays, especially in treating senile insomnia. However, the specific pharmacological features and underlying mechanisms of Polygala tenuifolia on treating senile insomnia remain unclear. Herein, aged insomnia rat model was established by injection of D-galactose (D-gal) and para-chlorophenylalanine (PCPA). Polygala tenuifolia (low-dose, medium-dose, high-dose) and diazepam was respectively given to aged insomnia rats for 7 days after the 45-day model establishment. Transcriptome results suggest the medium dose of Polygala tenuifolia can also increase the neurotransmitter levels of 5-HT and GABA, and decrease the level of Glu in the hippocampus of aged insomnia rats. 24 differentially expressed genes (DEGs) were overlapped among aged insomnia group, Polygala tenuifolia group, and diazepam group in transcriptome analysis. Fuom and Pcp2 had been identified to be downregulated by the treatment of Polygala tenuifolia. The metabolic rate of Polygala tenuifolia is relatively low compared with diazepam. The sedative effect of Polygala tenuifolia in aged insomnia may be related to neuro, metabolism and inflammatory pathways, especially GABAergic signaling pathway. The present results indicate the sedative and hypnotic effects of Polygala tenuifolia and its molecular mechanism, and provide more effective herb choice for the treatment of senile insomnia.