ABSTRACT
ObjectiveTo explore the mechanism of Huanglian Ejiaotang in intervening in insomnia based on 5-hydroxytryptamine (5-HT) system and gut microbiota. MethodFifty-five SPF-grade SD rats were randomly divided into normal group, model group, low-, medium-, and high-dose Huanglian Ejiaotang groups (1.925, 3.85, and 7.7 g·kg-1), and Estazolam group (0.1 mg·kg-1). Except for those in the normal group, the rats in the other five groups were subjected to sleep deprivation on a narrow platform for 12 hours daily for 21 consecutive days. After 14 days of drug intervention, the sleep, exploratory behavior, and depressive-like behavior of the rats were assessed using the pentobarbital sodium sleep synergistic test, the open field test, and the sugar preference test, respectively. Enzyme-linked immunosorbent assay (ELISA) was used to detect the levels of 5-HT, 5-hydroxyindoleacetic acid (5-HIAA), tryptophan hydroxylase (TPH), and monoamine oxidase-A (MAO-A). Real-time polymerase chain reaction (Real-time PCR) was used to measure the mRNA expression of the 5-HT1A receptor (5-HT1AR) and 5-HT2A receptor (5-HT2AR). Differences in gut microbiota among the groups were assessed using 16S rRNA sequencing, and the correlation between the 5-HT system and microbiota was revealed using redundancy analysis. ResultCompared with the normal group, the model group showed a prolonged sleep latency (P<0.05), reduced sleep maintenance (P<0.01), decreased central area activity time in the open field (P<0.01), and reduced sugar preference rate (P<0.05). Moreover, the model group also showed decreased levels of 5-HT, 5-HIAA, TPH, and MAO-A (P<0.01), decreased 5-HIAA/5-HT ratio (P<0.01), downregulated mRNA expression of 5-HT1AR (P<0.01), and upregulated mRNA expression of 5-HT2AR (P<0.05). The proportion of Firmicutes decreased, while that of Bacteroidetes increased, leading to a decreased Firmicutes/Bacteroidetes (F/B) ratio (P<0.05). Compared with the model group, the high-dose Huanglian Ejiaotang group exhibited a shortened sleep latency (P<0.01), and increased sleep maintenance (P<0.01). The low-dose Huanglian Ejiaotang group showed increased central area activity time (P<0.01) and an increased sugar preference rate (P<0.05). The high-dose Huanglian Ejiaotang group exhibited increased levels of 5-HT, 5-HIAA, TPH, and MAO-A (P<0.01), increased 5-HIAA/5-HT ratio (P<0.05), upregulated mRNA expression of 5-HT1AR (P<0.01), and downregulated mRNA expression of 5-HT2AR (P<0.05). The low-dose Huanglian Ejiaotang group displayed an increased proportion of Firmicutes and a decreased proportion of Bacteroidetes, resulting in an increased F/B ratio. At the phylum level, 5-HT, 5-HIAA, and MAO-A were positively correlated with Firmicutes and negatively correlated with Bacteroidetes. At the genus level, 5-HT, 5-HIAA, TPH, and MAO-A were negatively correlated with Prevotella and Lactobacillus and positively correlated with Blautia and Bacteroides. ConclusionHuanglian Ejiaotang can improve sleep deprivation-induced insomnia and depressive-like behavior by regulating the activity of the 5-HT system and the composition of gut microbiota.