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 investigate whether electroacupuncture (EA) at sensitized acupoints could reduce sympathetic-sensory coupling (SSC) and neurogenic inflammatory response by interfering with 5-hydroxytryptamine (5-HT)ergic neural pathways to relieve colitis and somatic referred pain, and explore the underlying mechanisms. METHODS: Rats were treated with 5% dextran sodium sulfate (DSS) solution for 7 days to establish a colitis model. Twelve rats were randomly divided into the control and model groups according to a random number table (n=6). According to the "Research on Rat Acupoint Atlas", sensitized acupoints and non-sensitized acupoints were determined. Rats were randomly divided into the control, model, Zusanli-EA (ST 36), Dachangshu-EA (BL 25), and Xinshu (BL 15) groups (n=6), as well as the control, model, EA, and EA + GR113808 (a 5-HT inhibitor) groups (n=6). The rats in the control group received no treatment. Acupuncture was administered on 2 days after modeling using the stimulation pavameters: 1 mA, 2 Hz, for 30 min, with sparse and dense waves, for 14 consecutive days. GR113808 was injected into the tail vein at 5 mg/kg before EA for 10 min for 7 consecutive days. Mechanical sensitivity was assessed with von Frey filaments. Body weight and disease activity index (DAI) scores of rats were determined. Hematoxylin and eosin staining was performed to observe colon histopathology. SSC was analyzed by immunofluorescence staining. Immunohistochemical staining was performed to detect 5-HT and substance P (SP) expressions. The calcitonin gene-related peptide (CGRP) in skin tissue and tyrosine hydroxylase (TH) protein levels in DRG were detected by Western blot. The levels of hyaluronic acid (HA), bradykinin (BK), prostaglandin I2 (PGI2) in skin tissue, 5-HT, tryptophan hydroxylase 1 (TPH1), serotonin transporters (SERT), 5-HT 3 receptor (5-HT3R), and 5-HT 4 receptor (5-HT4R) in colon tissue were measured by enzyme-linked immunosorbent assay (ELISA). RESULTS: BL 25 and ST 36 acupoints were determined as sensitized acupoints, and BL 15 acupoint was used as a non-sensitized acupoint. EA at sensitized acupoints improved the DAI score, increased mechanical withdrawal thresholds, and alleviated colonic pathological damage of rats. EA at sensitized acupoints reduced SSC structures and decreased TH and CGRP expression levels (P<0.05). Furthermore, EA at sensitized acupoints reduced BK, PGI2, 5-HT, 5-HT3R and TPH1 levels, and increased HA, 5-HT4R and SERT levels in colitis rats (P<0.05). GR113808 treatment diminished the protective effect of EA at sensitized acupoints in colitis rats (P<0.05). CONCLUSION EA at sensitized acupoints alleviated DSS-induced somatic referred pain in colitis rats by interfering with 5-HTergic neural pathway, and reducing SSC inflammatory response.
Rats ; Animals ; Electroacupuncture ; Rats, Sprague-Dawley ; Serotonin ; Acupuncture Points ; Pain, Referred ; Calcitonin Gene-Related Peptide ; Signal Transduction ; Colitis/therapy* ; Indoles ; Sulfonamides

OBJECTIVE: To observe the clinical effect of bloodletting at auricular dorsal vein combined with auricular point sticking on menstrual migraine (MM) of qi stagnation and blood stasis, and explore its possible mechanism. METHODS: A total of 102 cases of MM with qi stagnation and blood stasis were randomly divided into an observation group (51 cases, 3 cases dropped off) and a control group (51 cases, 2 cases dropped off). The patients in the observation group were treated with bloodletting at auricular dorsal vein combined with auricular point sticking. The bloodletting was performed at vein at upper 1/3 of the dorsalis near the ear helix; the auricular point sticking was performed at Pizhixia (AT₄), Neifenmi (CO₁₈), Jiaogan (AH_6a), Nie (AT₂), Zhen (AT₃), Shenmen (TF₄) and Yidan (CO₁₁). The auricular points of both ears were alternate used. From 7 days before the onset of menstruation, bloodletting at auricular dorsal vein was given once every 7 days, 3 times were taken as a course of treatment, and 1 course of treatment was given; the auricular point sticking was given once every 3 days, and 6 times of treatment were given. The patients in the control group were treated with oral administration of flunarizine hydrochloride capsules. From 7 days before the onset of menstruation, flunarizine hydrochloride was given 2 capsules per time, once a day for 3 weeks. The menstrual headache index and visual analogue scale (VAS) score of the two groups were observed before treatment, one menstrual cycle into treatment and the first and the second menstrual cycle after treatment; the migraine-specific quality of life questionnaire (MSQ) score and the serum levels of estradiol (E₂) and 5-hydroxytryptamine (5-HT) were compared before treatment and one menstrual cycle into treatment; the clinical efficacy was evaluated at one menstrual cycle into treatment. RESULTS: Compared before treatment, the menstrual headache index and VAS scores were reduced at one menstrual cycle into treatment and the first and second menstrual cycle after treatment in the two groups (P<0.05), and those in the observation group were lower than the control group (P<0.05). Compared before treatment, the MSQ scores and the serum levels of E₂ and 5-HT in the two groups were increased at one menstrual cycle into treatment (P<0.05), and those in the observation group were higher than the control group (P<0.05). The total effective rate was 95.8% (46/48) in the observation group, which was higher than 73.5% (36/49) in the control group (P<0.05). CONCLUSION Bloodletting at auricular dorsal vein combined with auricular point sticking could relieve headache intensity, improve the quality of life in patients with MM of qi stagnation and blood stasis, which may be achieved by raising the serum levels of E₂ and 5-HT to improve the level of hormone in the body.
Female ; Humans ; Acupuncture, Ear ; Bloodletting ; Serotonin ; Capsules ; Flunarizine ; Qi ; Quality of Life ; Migraine Disorders/drug therapy* ; Headache/therapy* ; Treatment Outcome ; Acupuncture Points

OBJECTIVE: To observe the effects of electroacupuncture at "Siguan" points on behavior, colonic 5-hydroxytryptamine (5-HT) and fecal short-chain fatty acids (SCFAs) in rats with post-stroke depression (PSD), and explore the effect mechanism of electroacupuncture at Siguan points on PSD. METHODS: Fifty SD rats were randomly divided into a sham-operation group, a stroke group, a PSD group, a drug group and an electroacupuncture group, with 10 rats in each one. The stroke model was established by middle cerebral artery occlusion (MCAO) method in the stroke group; except for the sham-operation group, the rats in the other groups were intervened with MCAO combined with solitary and chronic unpredictable mild stress (CUMS) to establish PSD model. In the electroacupuncture group, electroacupuncture was delivered at "Hegu" (LI 4) and "Taichong" (LR 3), with disperse-dense wave, 2 Hz/10 Hz in frequency, for 30 min in each intervention, once daily, for consecutive 21 days. Simultaneously, distilled water (0.01 L•kg^-1•d^-1) was administrated intragastrically. Fluoxetine solution (2.33 mg•kg^-1•d^-1) was given by gavage , once a day and for 21 days in the drug group. The same procedure of fixation and gavage with distilled water were adopted in the sham-operation group, the stroke group and the PSD group. Separately, before stroke modeling, after PSD modeling and after 21-day intervention, the consumption of sugar water and the scores of horizontal movement and vertical movement in open-field test were observed. After 21-day intervention, the content of colonic 5-HT was detected by immunohistochemical method, and that of fecal SCFAs was determined by gas chromatography mass spectrometry. RESULTS: After PSD modeling, compared with the stroke group, the sugar water consumption, the horizontal movement scores and vertical movement scores of the open-field test were all reduced in the PSD group, the drug group and the electroacupuncture group (P<0.05). After 21-day intervention, the sugar water consumption and the scores of horizontal movement and vertical movement of the open-field test were increased in the drug group and the electroacupuncture group (P<0.05) when compared with the PSD group; and the horizontal movement score in the electroacupuncture group was lower than that of the drug group (P<0.05). Compared with the sham-operation group, the contents of total fecal SCFAs and acetic acid were lower in the stroke group (P<0.05), and the contents of colonic 5-HT and total fecal SCFAs, acetic acid, propionic acid and butyric acid were reduced in the PSD group (P<0.05). In comparison with the PSD group, the contents of colonic 5-HT and total fecal SCFAs, acetic acid and propionic acid were increased in the drug group and the electroacupuncture group (P<0.05); and the content of colonic 5-HT in the electroacupuncture group was lower than that of the drug group (P<0.05). The level of colonic 5-HT was positively correlated with the contents of total fecal SCFAs and propionic acid (r=0.424, P=0.005; r=0.427, P=0.004). CONCLUSION Electroacupuncture at "Siguan" points can relieve the depression-like behavior of PSD rats, and its underlying mechanism may be related to the regulation of fecal SCFAs, which affects the release of colonic 5-HT.
Animals ; Rats ; Rats, Sprague-Dawley ; Propionates ; Serotonin ; Depression/therapy* ; Electroacupuncture ; Fatty Acids, Volatile ; Stroke/complications* ; Acetic Acid ; Butyric Acid ; Water

OBJECTIVE: To observe the effects of moxa smoke through olfactory pathway on learning and memory ability in rapid aging (SAMP8) mice, and to explore the action pathway of moxa smoke. METHODS: Forty-eight six-month-old male SAMP8 mice were randomly divided into a model group, an olfactory dysfunction group, a moxa smoke group and an olfactory dysfunction + moxa smoke group, with 12 mice in each group. Twelve age-matched male SAMR1 mice were used as the blank group. The olfactory dysfunction model was induced in the olfactory dysfunction group and the olfactory dysfunction + moxa smoke group by intraperitoneal injection of 3-methylindole (3-MI) with 300 mg/kg, and the moxa smoke group and the olfactory dysfunction + moxa smoke group were intervened with moxa smoke at a concentration of 10-15 mg/m³ for 30 min per day, with a total of 6 interventions per week. After 6 weeks, the emotion and cognitive function of mice was tested by open field test and Morris water maze test, and the neuronal morphology in the CAI area of the hippocampus was observed by HE staining. The contents of neurotransmitters (glutamic acid [Glu], gamma-aminobutyric acid [GABA], dopamine [DA], and 5-hydroxytryptamine [5-HT]) in hippocampal tissue of mice were detected by ELISA. RESULTS: The mice in the blank group, the model group and the moxa smoke group could find the buried food pellets within 300 s, while the mice in the olfactory dysfunction group and the olfactory dysfunction + moxa smoke group took more than 300 s to find them. Compared with the blank group, the model group had increased vertical and horizontal movements (P<0.05) and reduced central area residence time (P<0.05) in the open field test, prolonged mean escape latency on days 1-4 (P<0.05), and decreased search time, swimming distance and swimming distance ratio in the target quadrant of the Morris water maze test, and decreased GABA, DA and 5-HT contents (P<0.05, P<0.01) and increased Glu content (P<0.05) in hippocampal tissue. Compared with the model group, the olfactory dysfunction group had increased vertical movements (P<0.05), reduced central area residence time (P<0.05), and increased DA content in hippocampal tissue (P<0.05); the olfactory dysfunction + moxa smoke group had shortened mean escape latency on days 3 and 4 of the Morris water maze test (P<0.05) and increased DA content in hippocampal tissue (P<0.05); the moxa smoke group had prolonged search time in the target quadrant (P<0.05) and increased swimming distance ratio, and increased DA and 5-HT contents in hippocampal tissue (P<0.05, P<0.01) and decreased Glu content in hippocampal tissue (P<0.05). Compared with the olfactory dysfunction group, the olfactory dysfunction + moxa smoke group showed a shortened mean escape latency on day 4 of the Morris water maze test (P<0.05). Compared with the moxa smoke group, the olfactory dysfunction + moxa smoke group had a decreased 5-HT content in the hippocampus (P<0.05). Compared with the blank group, the model group showed a reduced number of neurons in the CA1 area of the hippocampus with a disordered arrangement; the olfactory dysfunction group had similar neuronal morphology in the CA1 area of the hippocampus to the model group. Compared with the model group, the moxa smoke group had an increased number of neurons in the CA1 area of the hippocampus that were more densely packed. Compared with the moxa smoke group, the olfactory dysfunction + moxa smoke group had a reduced number of neurons in the CA1 area of the hippocampus, with the extent between that of the moxa smoke group and the olfactory dysfunction group. CONCLUSION The moxa smoke could regulate the contents of neurotransmitters Glu, DA and 5-HT in hippocampal tissue through olfactory pathway to improve the learning and memory ability of SAMP8 mice, and the olfactory is not the only effective pathway.
Male ; Animals ; Mice ; Olfactory Pathways ; Smoke/adverse effects* ; Serotonin ; Aging ; Dopamine ; Olfaction Disorders/etiology*

Circadian clock is an internal mechanism evolved to adapt to cyclic environmental changes, especially diurnal changes. Keeping the internal clock in synchronization with the external clock is essential for health. Mismatch of the clocks due to phase shift or disruption of molecular clocks may lead to circadian disorders, including abnormal sleep-wake cycles, as well as disrupted rhythms in hormone secretion, blood pressure, heart rate, body temperature, etc. Long-term circadian disorders are risk factors for various common critical diseases such as metabolic diseases, cardiovascular diseases, and tumor. To prevent or treat the circadian disorders, scientists have conducted extensive research on the function of circadian clocks and their roles in the development of diseases, and screened hundreds of thousands of compounds to find candidates to regulate circadian rhythms. In addition, melatonin, light therapy, exercise therapy, timing and composition of food also play a certain role in relieving associated symptoms. Here, we summarized the progress of both drug- and non-drug-based approaches to prevent and treat circadian clock disorders.
Circadian Rhythm ; Circadian Clocks ; Melatonin/physiology*

The present article was aimed to compare the effectiveness of different induction methods for depression models. Kunming mice were randomly divided into chronic unpredictable mild stress (CUMS) group, corticosterone (CORT) group, and CUMS+CORT (CC) group. The CUMS group received CUMS stimulation for 4 weeks, and the CORT group received subcutaneous injection of 20 mg/kg CORT into the groin every day for 3 weeks. The CC group received both CUMS stimulation and CORT administration. Each group was assigned a control group. After modeling, forced swimming test (FST), tail suspension test (TST) and sucrose preference test (SPT) were used to detect the behavioral changes of mice, and the serum levels of brain-derived neurotrophic factor (BDNF), 5-hydroxytryptamine (5-HT) and CORT were detected with ELISA kits. Attenuated total refraction (ATR) spectra of mouse serum were collected and analyzed. HE staining was used to detect morphological changes in mouse brain tissue. The results showed that the weight of model mice from the CUMS and CC groups decreased significantly. There was no significant change in immobility time of model mice from the three groups in FST and TST, while the glucose preference of model mice from the CUMS and CC groups was significantly reduced (P < 0.05). The serum 5-HT levels of model mice from the CORT and CC groups were significantly reduced, while the serum BDNF and CORT levels of model mice from the CUMS, CORT, and CC groups showed no significant changes. Compared with their respective control groups, the three groups showed no significant difference in the one-dimensional spectrum of serum ATR. The difference spectrum analysis results of the first derivative of the spectrogram showed that the CORT group had the greatest difference from its respective control group, followed by the CUMS group. The structures of hippocampus in the model mice from the three groups were all destroyed. These results suggest that both CORT and CC treatments can successfully construct a depression model, and the CORT model is more effective than the CC model. Therefore, CORT induction can be used to establish a depression model in Kunming mice.
Mice ; Animals ; Depression/etiology* ; Antidepressive Agents/pharmacology* ; Brain-Derived Neurotrophic Factor ; Serotonin

To investigate the antidepressant mechanism of Shenling Kaixin Granules(SLKX) in treating chronic unpredictable mild stress(CUMS) model rats. Ninety male SD rats were randomly divided into control group, model group, Shugan Jieyu Capsules(110 mg·kg~(-1)) group and SLKX low-(90 mg·kg~(-1)), medium-(180 mg·kg~(-1)), and high-dose(360 mg·kg~(-1)) groups. Depression rat model was replicated by CUMS method. After treatment, the behavioral changes of rats were evaluated by sugar preference, open field, elevated cross maze and forced swimming experiments. The contents of interleukin 1 beta(IL-1β), tumor necrosis factor α(TNF-α), brain-derived neurotrophic factor(BDNF) and 5-hydroxytryptamine(5-HT) in serum were determined by enzyme linked immunosorbent assay(ELISA), and the activities of superoxide dismutase(SOD) and catalase(CAT) in hippocampal CA1 region were also detected. Pathological changes in hippocampal CA1 region were detected by hematoxylin-eosin(HE) staining, and Western blot was used to determine the expression of nerve growth factor(NGF), BDNF, phospho-tyrosine kinase receptor(p-TrkB)/TrkB, phospho-cAMP-response element binding protein(p-CREB)/CREB, nuclear factor E2 related factor 2(Nrf2), heme oxygenase 1(HO-1), B-cell lymphoma-2(Bcl-2)/Bcl-2 associated X protein(Bax) and caspase-3 in hippocampal CA1 region. RESULTS:: showed that compared with the control group, the model group had decreased sugar preference, reduced number of entries and time spent in the center of open field and shortened total distance of movement, reduced number of entries and proportion of time spent in open arm, and increased number and time of immobility in forced swimming experiment. Additionally, the serum contents of IL-1β and TNF-α and the expression of caspase-3 were higher, while the contents of BDNF and 5-HT, the activities of SOD and CAT in hippocampal CA1 region, the expressions of NGF, BDNF, p-TrkB/TrkB, p-CREB/CREB, HO-1 and Bcl-2/Bax, and the Nrf2 nuclear translocation were lower in model group than in control group. Compared with the conditions in model group, the sugar preference, the number of entries and time spent in the center of open, total distance of movement, and the number of entries and proportion of time spent in open arm in treatment groups were increased while the number and time of immobility in forced swimming experiment were decreased; the serum contents of IL-1β and TNF-α and the expression of caspase-3 were down regulated, while the contents of BDNF and 5-HT, the activities of SOD and CAT in hippocampal CA1 region, the expressions of NGF, BDNF, p-TrkB/TrkB, p-CREB/CREB, HO-1, Bcl-2/Bax, and Nrf2 nuclear translocation were enhanced. In conclusion, SLKX might regulate the Nrf2 nucleus translocation by activating BDNF/TrkB/CREB pathway, lower oxidative stress damage in hippocampus, inhibit caspase-3 activity, and reduce apoptosis of hippocampal nerve cells, thereby playing an antidepressant role.
Rats ; Male ; Animals ; bcl-2-Associated X Protein/metabolism* ; Caspase 3/metabolism* ; Nerve Growth Factor/metabolism* ; Brain-Derived Neurotrophic Factor/metabolism* ; Signal Transduction ; Tumor Necrosis Factor-alpha/metabolism* ; Serotonin/metabolism* ; NF-E2-Related Factor 2/metabolism* ; Rats, Sprague-Dawley ; Antidepressive Agents/pharmacology* ; Hippocampus/metabolism* ; Superoxide Dismutase/metabolism* ; Sugars/pharmacology* ; Depression/genetics* ; Stress, Psychological/metabolism*

Objective To investigate the effects of formononetin (FMN) on cognitive behavior and inflammation in aging rats with chronic unpredictable mild stress (CUMS). Methods SD rats aged about 70 weeks were divided into healthy control group, CUMS model group, CUMS combined with 10 mg/kg FMN group, CUMS combined with 20 mg/kg FMN group and CUMS combined with 1.8 mg/kg fluoxetine hydrochloride (Flu) group. Except for healthy control group, other groups were stimulated with CUMS and administered drugs for 28 days. Sugar water preference, forced swimming experiment and open field experiment were used to observe the emotional behavior of rats in each group. HE staining was used to observe the pathological injury degree of brain equine area. The contents of 5-hydroxytryptamine (5-HT) and 5-hydroxyindoleacetic acid (5-HIAA) were detected by the kit. The apoptosis was tested by terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) in the brain tissue. The levels of tumor necrosis factor α (TNF-α), inducible nitric oxide synthase (iNOS) and interleukin 6 (IL-6) in peripheral blood were measured by ELISA. Western blot analysis was used to detect Bcl2, Bcl2 associated X protein (BAX), cleaved caspase-9, cleaved caspase-3, Toll-like receptor 4 (TLR4), myeloid differentiation factor 88 (MyD88), and phosphorylated nuclear factor κB p65 (p-NF-κB p65) in brain tissues. Results Compared with CUMS model group, sugar water consumption, open field activity time, open field travel distance and swimming activity time significantly increased in the CUMS combined with 20 mg/kg FMN group and the CUMS combined with 1.8 mg/kg Flu group. The number of new outarm entry increased significantly, while the number of initial arm entry and other arm entry decreased significantly. The pathological damage of brain equine area was alleviated, and the contents of 5-HT and 5-HIAA were significantly increased. The ratio of BAX/Bcl2 and the expression of cleaved caspase-9 and cleaved caspase-3 protein as well as the number of apoptotic cells were significantly decreased. The contents of TNF-α, iNOS and IL-6 were significantly decreased. The protein levels of TLR4, MyD88 and p-NF-κB p65 were significantly decreased. Conclusion FMN can inhibit the release of inflammatory factors by blocking NF-κB pathway and improve cognitive and behavioral ability of CUMS aged rats.
Rats ; Animals ; Horses ; NF-kappa B/metabolism* ; Signal Transduction ; bcl-2-Associated X Protein/metabolism* ; Toll-Like Receptor 4/metabolism* ; Caspase 3/metabolism* ; Caspase 9/metabolism* ; Interleukin-6/metabolism* ; Tumor Necrosis Factor-alpha/metabolism* ; Myeloid Differentiation Factor 88 ; Hydroxyindoleacetic Acid/pharmacology* ; Serotonin/metabolism* ; Rats, Sprague-Dawley ; Hippocampus/metabolism* ; Cognition

OBJECTIVES: To study the protective effect of melatonin (Mel) against oxygen-induced retinopathy (OIR) in neonatal mice and the role of the HMGB1/NF-κB/NLRP3 axis. METHODS: Neonatal C57BL/6J mice, aged 7 days, were randomly divided into a control group, a model group (OIR group), and a Mel treatment group (OIR+Mel group), with 9 mice in each group. The hyperoxia induction method was used to establish a model of OIR. Hematoxylin and eosin staining and retinal flat-mount preparation were used to observe retinal structure and neovascularization. Immunofluorescent staining was used to measure the expression of proteins and inflammatory factors associated with the HMGB1/NF-κB/NLRP3 axis and lymphocyte antigen 6G. Colorimetry was used to measure the activity of myeloperoxidase. RESULTS: The OIR group had destruction of retinal structure with a large perfusion-free area and neovascularization, while the OIR+Mel group had improvement in destruction of retinal structure with reductions in neovascularization and perfusion-free area. Compared with the control group, the OIR group had significant increases in the expression of proteins and inflammatory factors associated with the HMGB1/NF-κB/NLRP3 axis, the expression of lymphocyte antigen 6G, and the activity of myeloperoxidase (P<0.05). Compared with the OIR group, the OIR+Mel group had significant reductions in the above indices (P<0.05). Compared with the control group, the OIR group had significant reductions in the expression of melatonin receptors in the retina (P<0.05). Compared with the OIR group, the OIR+Mel group had significant increases in the expression of melatonin receptors (P<0.05). CONCLUSIONS Mel can alleviate OIR-induced retinal damage in neonatal mice by inhibiting the HMGB1/NF-κB/NLRP3 axis and may exert an effect through the melatonin receptor pathway.
Animals ; Mice ; HMGB1 Protein ; Melatonin/therapeutic use* ; Mice, Inbred C57BL ; NF-kappa B ; NLR Family, Pyrin Domain-Containing 3 Protein ; Oxygen/adverse effects* ; Peroxidase ; Receptors, Melatonin ; Retinal Diseases/drug therapy*