Background  The incidence of insomnia is increasing, which affects human physical and mental health. The main active ingredients of Pinellia Ternata and Coix Seed (BX-YYR) include baicalein, β-sitosterol, dousterol, etc., but its specific mechanism of action is still unclear.

  Objective  To investigate the regulatory effects of BX-YYR on Orexin and its receptors and apoptosis-related factors in 4-Chloro-DL-phenylalanine (PCPA) insomnia model rats.

  Methods  PCPA was applied to induce insomnia rat models, the experimental rats were divided into normal group (N), model group (M), diazepam group (D), low dose of BX-YYR (ZL), medium dose of BX-YYR (ZM), and high dose of BX-YYR (ZH) group, with 15 rats in each group. Each group was given corresponding intragastric administration at 10 mL/kg body weight for 7 consecutive days. Pentobarbital sodium correction and open field experiments were performed. HE staining was used to observe the hippocampus structure, immunohistochemistry for the hippocampal B-cell lymphoma-2 gene (Bcl-2), ELISA was used to detect the serum tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), IL-2, IL-6, and Orexin, RT-PCR for the expression of OX1R and OX2R mRNA, and Western blotting for the protein expression of OX1R and OX2R.

  Results  The pentobarbital sodium correction experiment significantly prolonged sleep latency and shortened sleep duration in insomnia model rats (all P＜0.01). In the open field experiment, the total activity distance of the model rats decreased, the distance into the central grid and the number of modifications increased (all P＜0.01). HE staining showed that the neuron morphology and structure of hippocampus CA1 area in M group were severely damaged, while the damage in Chinese medicine dose groups were relatively reduced. Immunohistochemistry showed that compared with M group, the proportion of the hippocampal Bcl2 positive signal area in ZH group increased (P＜0.01). ELISA showed that compared with M group, the serum TNF-α, IL-1β, IL-2 and IL-6 in the D, ZL, ZM, ZH groups were significantly reduced (all P＜0.05), and the Orexin levels of serum and hippocampus in D, ZM, ZH groups were also significantly reduced (all P＜0.01). RT-PCR showed that compared with M group, the expression of hippocampal OX1R mRNA in each dose group of Chinese medicine decreased (all P＜0.05). Western blot detection showed that compared with M group, the hippocampus OX1R expression levels in ZL, ZM, ZH groups decreased (all P＜0.01), while the hippocampus OX2R expression levels in D, ZL group increased (all P＜0.05).

  Conclusion  BX-YYR can improve the sleep quality of PCPA insomnia model rats and regulate the sera levels of TNF-α, IL-1β, IL-2, and L-6. The mechanism of action may be related to the regulation of hippocampal Orexin and its receptors OX1R and OX2R expression, upregulation of Bcl-2 expression and inhibition of hippocampal neuronal cell apoptosis.