Circadian rhythm is an essential biological process that regulates the sleep-wake cycle，hormone secretion，and metabolism，and the stability of circadian rhythm is crucial for maintaining normal cognitive function. Melatonin （MT），a key hormone secreted by the pineal gland，is involved in the regulation of circadian rhythm and thus has a significant impact on cognitive function. This article systematically reviews the multiple mechanisms by which MT regulates cognitive function through circadian rhythm，including improving sleep quality，promoting the clearance of metabolic waste by the glymphatic system，exerting antioxidant and anti-inflammatory effects，and regulating neuronal activity and the improvement of synaptic plasticity. In addition，this article also discusses the association between circadian rhythm disorders and neurodegenerative diseases. Future studies are needed in the future to further clarify the neuroprotective mechanisms of MT，in order to provide new insights for the prevention and treatment of cognitive impairment.
Melatonin

OBJECTIVE: To observe the effects of Tiaoshu Anshen (regulating the hinge and calming the mind) acupuncture on sleep quality and serum levels of 5-hydroxytryptamine (5-HT) and dopamine (DA) in patients with chronic insomnia. METHODS: A total of 58 patients with chronic insomnia were randomly divided into an acupuncture group and a medication group, 29 cases in each group. Tiaoshu Anshen acupuncture was applied at Baihui (GV20) and bilateral Shenmen (HT7), Sanyinjiao (SP6), Benshen (GB13) in the acupuncture group, once a day, 1-day interval was taken after 6 consecutive days of treatment. Estazolam tablet was given orally before bed in the medication group, 1 mg each time. The 4-week treatment was required in both groups. Before and after treatment, the sleep quality was assessed by Pittsburgh sleep quality index (PSQI) and polysomnography (PSG), the serum levels of 5-HT and DA were detected by ELISA. RESULTS: After treatment, the item scores and total scores of PSQI were decreased compared with those before treatment in the two groups (P<0.05); in the acupuncture group, the scores of sleep quality, sleep latency, sleep time, sleep efficiency, sleep disorders and total score of PSQI were lower than those in the medication group (P<0.05). After treatment, the total sleep time (TST) was prolonged (P<0.05), the sleep latency (SL) and wake after sleep onset (WASO) were shortened (P<0.05), the sleep efficiency (SE%), percentage of non-rapid eye movement stage 3 (N3%), percentage of rapid eye movement stage (REM%) and serum levels of 5-HT were increased (P<0.05) compared with those before treatment; the percentage of non-rapid eye movement stage 1 (N1%), percentage of non-rapid eye movement stage 2 (N2%) and serum levels of DA were decreased (P<0.05) compared with those before treatment in the two groups. After treatment, in the acupuncture group, TST was longer, while SL and WASO were shorter than those in the medication group (P<0.05), SE%, N3%, REM% and serum level of 5-HT were higher, while N1%, N2% and serum level of DA were lower than those in the medication group (P<0.05). CONCLUSION Tiaoshu Anshen acupuncture may improve the sleep quality by regulating the serum neurotransmitter levels i.e. 5-HT and DA in patients with chronic insomnia.
Humans ; Sleep Initiation and Maintenance Disorders/physiopathology* ; Male ; Acupuncture Therapy ; Female ; Middle Aged ; Adult ; Serotonin/blood* ; Sleep Quality ; Acupuncture Points ; Dopamine/blood* ; Aged ; Neurotransmitter Agents/blood* ; Young Adult

OBJECTIVE: To observe the effect of electroacupuncture (EA) at "Hegu" (LI4) and "Taichong" (LR3) on DNA methylation of the solute carrier family 6 member 4 (SLC6A4) gene promoter region in the hippocampus of depressed rats, and to explore the potential antidepressant mechanism of EA. METHODS: Thirty male Sprague-Dawley rats were randomly divided into a blank group, a model group, a medication group, a 5-Azacytidine (5-AZA) group, and an EA group, 6 rats in each group. Depression models were established in the model group, the medication group, the 5-AZA group, and the EA group using chronic unpredictable mild stress (CUMS) combined with solitary housing. The medication group was treated with intragastric administration of fluoxetine hydrochloride capsules; the 5-AZA group was treated with intraperitoneal injection of 5-AZA; the EA group was treated with EA at bilateral "Hegu" (LI4) and "Taichong" (LR3), with disperse-dense wave, frequency of 2 Hz/100 Hz, and intensity of 1-1.2 mA, 20 min each session. All the treatment was given in three groups once daily for 21 consecutive days. Behavioral changes were evaluated by sucrose preference test, open field test, and novelty-suppressed feeding test. Serum levels of serotonin (5-HT), dopamine (DA), and norepinephrine (NE) were measured by ELISA. The expression of SLC6A4 and 5-HT1AR protein and mRNA in hippocampus was detected by Western blot and real-time quantitative PCR, respectively. DNA methylation status of the SLC6A4 promoter region in hippocampal tissue was analyzed by bisulfite sequencing PCR (BSP). RESULTS: Compared with the blank group, the model group showed decreased sucrose preference, reduced total locomotor distance, and prolonged latency to feeding (P<0.05), decreased serum 5-HT, DA, and NE levels (P<0.05), downregulated hippocampal SLC6A4 and 5-HT1AR protein and mRNA expression (P<0.05), and increased CpG site methylation rate of the SLC6A4 promoter region (P<0.05). Compared with the model group, the medication group, the 5-AZA group, and the EA group exhibited increased sucrose preference, increased total locomotor distance, shortened latency to feeding (P<0.05), elevated serum 5-HT, DA, and NE levels (P<0.05), upregulated hippocampal SLC6A4 and 5-HT1AR protein and mRNA expression (P<0.05), and reduced CpG site methylation rate of the SLC6A4 promoter (P<0.05). Compared with the medication group and the 5-AZA group, the EA group showed higher sucrose preference, greater total locomotor distance, shorter latency to feeding (P<0.05), and increased serum DA and NE levels (P<0.05). CONCLUSION EA could improve depressive behaviors in depressed rat models. The underlying mechanism may involve inhibition of SLC6A4 hypermethylation in the hippocampus on the serotonergic system, upregulation of SLC6A4 and 5-HT1AR protein and mRNA expression, and elevation of monoamine neurotransmitters such as 5-HT.
Animals ; Electroacupuncture ; Male ; Hippocampus/metabolism* ; Rats, Sprague-Dawley ; Rats ; Acupuncture Points ; DNA Methylation ; Depression/metabolism* ; Promoter Regions, Genetic ; Serotonin Plasma Membrane Transport Proteins/metabolism* ; Humans

Neuropathic pain, often featuring allodynia, imposes significant physical and psychological burdens on patients, with limited treatments due to unclear central mechanisms. Addressing this challenge remains a crucial unsolved issue in pain medicine. Our previous study, using protein kinase C gamma (PKCγ)-tdTomato mice, highlights the spinal feedforward inhibitory circuit involving PKCγ neurons in gating neuropathic allodynia. However, the regulatory mechanisms governing this circuit necessitate further elucidation. We used diverse transgenic mice and advanced techniques to uncover the regulatory role of the descending serotonin (5-HT) facilitation system on spinal PKCγ neurons. Our findings revealed that 5-HT neurons from the rostral ventromedial medulla hyperpolarize spinal inhibitory interneurons via 5-HT_2C receptors, disinhibiting the feedforward inhibitory circuit involving PKCγ neurons and exacerbating allodynia. Inhibiting spinal 5-HT_2C receptors restored the feedforward inhibitory circuit, effectively preventing neuropathic allodynia. These insights offer promising therapeutic targets for neuropathic allodynia management, emphasizing the potential of spinal 5-HT_2C receptors as a novel avenue for intervention.
Animals ; Neuralgia/physiopathology* ; Protein Kinase C/metabolism* ; Receptor, Serotonin, 5-HT2C/metabolism* ; Hyperalgesia/physiopathology* ; Mice, Transgenic ; Mice ; Spinal Cord/metabolism* ; Serotonin/metabolism* ; Male ; Neurons/metabolism* ; Mice, Inbred C57BL

Chemotherapy-induced peripheral neurotoxicity (CIPN) is a severe dose-limiting adverse event of chemotherapy. Presently, the mechanism underlying the induction of CIPN remains unclear, and no effective treatment is available. In this study, through metabolomics analyses, we found that nab-paclitaxel therapy markedly increased serum serotonin [5-hydroxtryptamine (5-HT)] levels in both cancer patients and mice compared to the respective controls. Furthermore, nab-paclitaxel-treated enterochromaffin (EC) cells showed increased 5-HT synthesis, and serotonin-treated Schwann cells showed damage, as indicated by the activation of CREB3L3/MMP3/FAS signaling. Venlafaxine, an inhibitor of serotonin and norepinephrine reuptake, was found to protect against nerve injury by suppressing the activation of CREB3L3/MMP3/FAS signaling in Schwann cells. Remarkably, venlafaxine was found to significantly alleviate nab-paclitaxel-induced CIPN in patients without affecting the clinical efficacy of chemotherapy. In summary, our study reveals that EC cell-derived 5-HT plays a critical role in nab-paclitaxel-related neurotoxic lesions, and venlafaxine co-administration represents a novel approach to treating chronic cumulative neurotoxicity commonly reported in nab-paclitaxel-based chemotherapy.
Paclitaxel/toxicity* ; Animals ; Albumins/adverse effects* ; Serotonin/metabolism* ; Mice ; Humans ; Male ; Female ; Venlafaxine Hydrochloride/therapeutic use* ; Neurotoxicity Syndromes/metabolism* ; Middle Aged ; Schwann Cells/metabolism* ; Peripheral Nervous System Diseases/drug therapy* ; Antineoplastic Agents

To explore the anti-depression effect of Suanzaoren Decoction(SZRD), the regulatory effects on endogenous metabolites in the liver of rats with depression induced by chronic unpredictable mild stress(CUMS) were analyzed by using LC-MS metabolomics. The rats were randomly divided into normal control group, model group, low-dose SZRD group, high-dose SZRD group, and positive drug group. The CUMS depression model was replicated by applying a variety of stimuli, such as fasting and water deprivation, ice water swimming, hot water swimming, day and night reversal, tail clamping, and restraint for rats. Modeling and treatment were conducted for 56 days. The behavioral indexes of rats in each group, including body weight, open field test, sucrose preference test, and tail suspension test, were observed. Plasma samples and liver tissue samples were collected, and the contents of 5-hydroxytryptamine(5-HT), dopamine(DA), and norepinephrine(NE) in plasma were measured using enzyme-linked immunosorbent assay(ELISA). Meanwhile, the regulatory effects of SZRD on the liver metabolic profile of CUMS model rats were analyzed by the LC-MS metabolomics method. The results show that SZRD can significantly improve the depression-like behavior of CUMS model rats and increase the neurotransmitter levels of 5-HT, DA, and NE in plasma. A total of 24 different metabolites in the rats' liver are identified using the LC-MS metabolomics method, and SZRD can reverse 13 of these metabolites. Metabolic pathway analysis indicates that nine metabolic pathways are found to be significantly associated with depression, and in the low-dose SZRD group, four pathways can be regulated, including pentose phosphate pathway, purine metabolism, inositol phosphate metabolism, and sphingolipid metabolism. In the high-dose SZRD group, two metabolic pathways can be regulated, including sphingolipid metabolism and glycerol glycerophospholipid metabolism. Sphingolipid metabolism is a metabolic pathway that can be regulated by SZRD at different doses, so it is speculated that it may be the primary pathway through which SZRD can alleviate metabolic disturbances in the liver of CUMS model rats.
Animals ; Rats ; Drugs, Chinese Herbal/administration & dosage* ; Metabolomics ; Depression/metabolism* ; Male ; Liver/drug effects* ; Rats, Sprague-Dawley ; Antidepressive Agents/administration & dosage* ; Serotonin/blood* ; Humans ; Disease Models, Animal ; Behavior, Animal/drug effects*

This study aims to observe the mind-tranquilizing effect of Fushen Decoction on mice and investigate its effects on the 5-hydroxytryptamine(5-HT) system and γ-aminobutyric acid(GABA) in the brain of the mouse model of 4-chloro-DL-phenylalanine(PCPA)-induced insomnia. ICR mice were administrated with coffee(1 g·kg~(-1)) for 3 days, and the effects of Fushen Decoction(10, 20, and 40 g·kg~(-1)) on the autonomic activities of normal mice and coffee-treated mice were observed. Furthermore, the effects of Fushen Decoction on the autonomic activity and sleep induced by a suprathreshold dose of pentobarbital sodium in the mouse model of PCPA(350 mg·kg~(-1) for 3 consecutive days)-induced insomnia were observed. The levels of tryptophan hydroxylase(TPH), 5-hydroxytryptophan(5-HTP), and 5-HT in the serum, as well as those of 5-HTP and 5-HT in the brain stem, hippocampus, and cortex, were measured by enzyme-linked immunosorbent assay(ELISA). The fluorescence intensity of 5-HT in the raphe nucleus, hippocampus, and cortex was measured by the immunofluorescence method. The protein levels of tryptophan hydroxylase-2(TPH2) and 5-HT_(1A) receptor(5-HT_(1A)R) in the brain stem, hippocampus, and cortex were measured by Western blot. The levels of GABA in the hypothalamus, hippocampus, and cortex were measured by ELISA and immunohistochemistry methods. The results showed that Fushen Decoction(20, 40 g·kg~(-1)) reduced the number of autonomous activities in normal mice, coffee-treated mice, and the mouse model of PCPA-induced insomnia, and prolonged the duration of sleep induced by a suprathreshold dose of pentobarbital sodium in the mouse model. Fushen Decoction(20, 40 g·kg~(-1)) elevated the levels of TPH, 5-HTP, and 5-HT in the serum, and TPH2, 5-HTP, 5-HT, and 5-HT_(1A)R in the brain stem, hippocampus, and cortex, and up-regulated GABA expression in the hypothalamus, cortex, and hippocampus of the mouse model of PCPA-induced insomnia. In conclusion, Fushen Decoction(20, 40 g·kg~(-1)) exerted a mind-tranquilizing effect on mice by up-regulating the expression of TPH2, enhancing the 5-HT system, and elevating the GABA level in the brain.
Animals ; Serotonin/genetics* ; Sleep Initiation and Maintenance Disorders/genetics* ; Mice ; Drugs, Chinese Herbal/administration & dosage* ; Male ; Mice, Inbred ICR ; gamma-Aminobutyric Acid/genetics* ; Disease Models, Animal ; Fenclonine/adverse effects* ; Tryptophan Hydroxylase/genetics* ; Brain/metabolism* ; Sleep/drug effects* ; Humans ; 5-Hydroxytryptophan/metabolism*

This study aims to investigate the mechanism through which Xiangshao Granules treat anxiety and depression using metabolomics and gut microbiota techniques, combined with animal experiments. Sixty female ICR mice were selected for the experiment and randomly divided into six groups: a control group, a model group, a low-dose Xiangshao Granules group, a medium-dose Xiangshao Granules group, a high-dose Xiangshao Granules group, and an estradiol(positive drug) group. Except for the control group, rats in other groups were induced for anxiety and depression model by ovariectomy(OVX) combined with chronic unpredictable mild stress(CUMS). After successful modeling, the mice received oral administration of Xiangshao Granules or estradiol for three weeks. Anxiety and depression behaviors in mice were evaluated using light-dark box tests, open field tests, and elevated plus-maze tests. The levels of substances closely related to anxiety and depression, such as serotonin(5-HT) and estrogen(E_2), were quantified in plasma and hippocampal tissue using enzyme-linked immunosorbent assay(ELISA). Metabolomics and 16S rDNA amplicon sequencing techniques were employed to analyze the regulatory effects of Xiangshao Granules on plasma metabolites and metabolic pathways in anxiety and depression mice, as well as their impact on the distribution of gut microbiota. Finally, the correlation between plasma metabolites and differential gut microbiota was constructed using the Spearman correlation coefficient method. Behavioral experimental results indicated that, compared to the control group, the model group exhibited significantly decreased dwell time in the light box, reduced total distance in the open field, and diminished dwell time in the open arm. In contrast, high dose of Xiangshao Granules were found to increase the dwell time in the light box and total distance in the open field. ELISA results indicated that the levels of 5-HT, gamma-aminobutyric acid(GABA), E_2 were significantly decreased, luteinizing hormone(LH), adrenocorticotropic hormone(ACTH), and corticosterone(CORT) were significantly elevated in the anxiety and depression mice, and treatment with middle, high dose of Xiangshao Granules reversed the levels of these substances. Additionally, in the anxiety and depression mouse model, the levels of follicle-stimulating hormone(FSH) were significantly increased, whereas middle, high dose of Xiangshao Granules decreased FSH levels. Metabolomics analysis revealed that Xiangshao Granules significantly changed the metabolic profile of the anxiety and depression mice, affecting central carbon metabolism, amino acid biosynthesis, and ABC transporter pathways. The results from 16S rDNA amplicon sequencing showed that Xiangshao Granules improved the relative abundance of genera such as Bacteroidia, Bacilli, Lactobacillales, and Lactobacillus. Spearman correlation analysis indicated a close association between specific differential gut microbiota and plasma differential metabolites. This study suggests that Xiangshao Granules significantly ameliorate anxiety and depression symptoms in mice by altering the levels of substances associated with these conditions, including 5-HT, GABA, E_2, LH, and ACTH. The metabolomics and gut microbiota data suggest that the therapeutic mechanism may be closely related to the regulation of amino acid biosynthesis, central carbon metabolism, and the alteration of key microbial community compositions.
Animals ; Drugs, Chinese Herbal/administration & dosage* ; Anxiety/microbiology* ; Depression/microbiology* ; Gastrointestinal Microbiome/drug effects* ; Mice ; Female ; Mice, Inbred ICR ; Metabolomics ; Serotonin/metabolism* ; Humans ; Disease Models, Animal ; Rats ; Behavior, Animal/drug effects*

Peganum harmala L. (P. harmala) is a significant economic and medicinal plant. The seeds of P. harmala have been extensively utilized in traditional Chinese medicine, Uighur medicine, and Mongolian medicine, as documented in the Drug Standard of the Ministry of Health of China. Twelve novel tryptamine-derived alkaloids (1-12) and eight known compounds (13-20) were isolated from P. harmala seeds. Compounds 1 and 2 represent the first reported instances of tryptamine-derived heteromers, comprising tryptamine and aniline fragments with previously undocumented C-3-N-1' linkage and C-3-C-4' connection, respectively. Compounds 3-5 were identified as indole-quinazoline heteromers, exhibiting a novel C-3 and NH-1' linkage between indole and quinazoline-derived fragments. Compound 6 demonstrates the dimerization pattern of C-C linked tryptamine-quinazoline dimer. Compound 8 represents a tryptamine-derived heterodimer with a distinctive carbon skeleton, featuring an unusual spiro-tricyclic ring (7) and conventional bicyclic tryptamine. Compounds 9-11 constitute novel 6/5/5/5 spiro-tetracyclic tryptamine-derived alkaloids presenting a unique ring system of tryptamine-spiro-pyrrolizine. Compounds 1-3 and 6-11 were identified as racemates. Compounds 2, 7, 9, 10, and 12 were confirmed via X-ray crystallographic analysis. All isolated compounds (1-20) exhibited varying degrees of antiviral efficacy against respiratory syncytial virus (RSV). Notably, the anti-RSV activity of compound 12 (IC₅₀ 5.01 ± 0.14 μmol·L^-1) surpassed that of the positive control (ribavirin, IC₅₀ 6.23 ± 0.95 μmol·L^-1), as validated through plaque reduction and immunofluorescence assays. The identification of anti-RSV compounds from P. harmala seeds may enhance the development and application of this plant in antiviral therapeutic products.
Antiviral Agents/isolation & purification* ; Tryptamines/isolation & purification* ; Peganum/chemistry* ; Seeds/chemistry* ; Alkaloids/isolation & purification* ; Molecular Structure ; Humans ; Respiratory Syncytial Viruses/drug effects* ; Plant Extracts/pharmacology* ; Drugs, Chinese Herbal/pharmacology*

The 5-hydroxytryptamine 2A receptor (5-HT_2AR) is one of the key targets in the development of novel antidepressants. To develop new antidepressants targeting the 5-HT_2A receptor, this study established a high-throughput screening method for drugs targeting the 5-HT_2A receptor based on the principle of detecting calcium flux signals. The immunofluorescence assay and western blotting were employed to evaluate receptor expression levels in the 5-HT_2AR-CHO cell line. The reaction system parameters, including cell seeding density, DMSO concentration, and dye incubation time, were optimized with Z'-factor and signal window values as evaluation indicators. The specificity, precision, stability, and applicability of the method were assessed. Results indicated that the 5-HT_2AR-CHO cell line stably expressed high levels of the 5-HT_2A receptor. The optimized screening method involved a reaction system with 10 000 cells/well, 0.2% DMSO, and 2 h incubation with Calcium 6 dye. The method demonstrated excellent specificity, with inter-batch precision below 10% for the detection of 5-hydroxytryptamine (5-HT) at low, medium, and high concentrations. Testing four compounds that target the 5-HT_2A receptor- agonists 2,5-dimethoxy-4-iodoamphetamine (DOI), 5-methoxy-N,N-dimethyltryptamine (5-MeO-DMT), and lysergic acid diethylamide (LSD), along with the antagonist MDL100907-yielded Z'-factors (at EC₈₀) greater than 0.85 and signal window values over 0.91. The EC₅₀ values of these compounds were in the nanomolar range, and their potency rank order aligned with previously reported data, confirming the reliability of the established method. When being applied to the detection of 38 known active compounds, the method efficiently identified 5-HT_2A receptor agonists and antagonists while showing no response to non-target compounds. In conclusion, this study successfully constructs a high-throughput screening approach for 5-HT_2A receptor-targeting drugs based on calcium flux signals. The method possesses strong specificity, high sensitivity, and robust stability, being suitable for screening antidepressants targeting the 5-HT_2A receptor.
High-Throughput Screening Assays/methods* ; Receptor, Serotonin, 5-HT2A/metabolism* ; Animals ; CHO Cells ; Cricetulus ; Calcium Signaling/drug effects* ; Antidepressive Agents/pharmacology* ; Humans ; Serotonin 5-HT2 Receptor Antagonists/pharmacology* ; Calcium/metabolism*