Enhanced antidepressant-like effects of electroacupuncture combined with citalopram in a rat model of depression

Efficacy and mechanism of acupuncture in animal models of depressive-like behaviors: a systematic review and meta-analysis

Background

Many studies have investigated the efficacy of acupuncture in treating depression, but the mechanism of acupuncture for depression is still controversial and there is a lack of meta-analysis of mechanisms. Consequently, we investigated acupuncture's efficacy and mechanism of depression.

Methods

We searched the Cochrane Library, PubMed, EMBASE, Web of Science. The SYRCLE Risk of Bias Tool was used to assess bias risk. Meta-analysis was performed using Stata 15.0 for indicators of depression mechanisms, body weight and behavioral tests.

Results

A total of 22 studies with 497 animals with depressive-like behaviors were included. Meta-analysis showed that acupuncture significantly increased BDNF [SMD = 2.40, 95% CI (1.33, 3.46); I2 = 86.6%], 5-HT [SMD = 2.28, 95% CI (1.08, 3.47); I2 = 87.7%] compared to the control group (p < 0.05), and significantly reduced IL-1β [SMD = -2.33, 95% CI (-3.43, -1.23); I2 = 69.6%], CORT [SMD = -2.81, 95% CI (-4.74, -0.87); I2 = 86.8%] (p < 0.05). Acupuncture improved body weight [SMD = 1.35, 95% CI (0.58, 2.11); I2 = 84.5%], forced swimming test [SMD = -1.89, 95% CI (-2.55, -1.24); I2 = 76.3%], open field test (crossing number [SMD = 3.08, 95% CI (1.98, 4.17); I2 = 86.7%], rearing number [SMD = 2.53, 95% CI (1.49, 3.57); I2 = 87.0%]) (p < 0.05) compared to the control group.

Conclusion

Acupuncture may treat animals of depressive-like behaviors by regulating neurotrophic factors, neurotransmitters, inflammatory cytokines, neuroendocrine system.

Systematic review registration

https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42023403318, identifier (CRD42023403318).

Antidepressant-Like Effects of Edaravone and Minocycline: Investigation of Oxidative Stress, Neuroinflammation, Neurotrophic, and Apoptotic Pathways

Depression is a very common mental disorder and mechanism that is associated with mitochondrial dysfunction. In the present study, we examined the mechanisms of action of isolated brain mitochondria in rats with depression for the first time. This will help identify the mitochondrial protective pathways of the two drugs and shed light on new therapeutic goals for developing antidepressants. Forced swimming, tail suspension, and sucrose preference tests were used to assess depressive-like behaviors and the oxidative stress factors of brain tissue, and measure the gene expression of apoptotic and anti-apoptotic, neuroplasticity, and neuroinflammatory factors by RT-PCR and acetylcholinesterase (AChE) activity in brain tissue (hippocampus and prefrontal) and the serum levels of corticosterone and fasting blood sugar. The results showed that the separation of neonatal rats from their mothers induced depressive-like behaviors, weight loss, mitochondrial dysfunction, increased expression of genes involved in neuroinflammation, apoptosis, genes involved in the depressive process, and decreased expression of genes involved in mood in both the hippocampus and prefrontal cortex. Maternal separation increased serum corticosterone levels, caused dysfunction of the cholinergic system, and also increased AChE activity. Treatment with different concentrations of minocycline and edaravone (1, 20, and 50 mg/kg), 5MTHF, and citalopram for 14 days showed that these drugs improved depression-like behaviors and mitochondrial function. It also reduced the expression of genes involved in neuroinflammation, apoptosis, and depression and increased the expression of genes involved in mood. In conclusion, minocycline and edaravone have neuroprotective, mitochondrial protective, antioxidant, anti-inflammatory, and anti-apoptotic effects against depressive-like behaviors caused by chronic stress.

Electroacupuncture Attenuated Anxiety and Depression-Like Behavior via Inhibition of Hippocampal Inflammatory Response and Metabolic Disorders in TNBS-Induced IBD Rats

This study was designed to explore the potential mechanisms of electroacupuncture (EA) in treating inflammatory bowel disease- (IBD-) related anxiety and mood disorders. A colitis model was induced in rats with 2, 4, 6-trinitrohydrosulfonic acid (TNBS), followed by ST36 and SP6 targeted therapy by EA or sham EA treatment. The elevated plus maze (EPM) and open-field test (OFT) were performed to assess the state of anxiety and depression-like behavior. Tests were carried out by 16S rDNA amplification sequence, ¹H nuclear magnetic resonance (¹H NMR) spectroscopy, immunofluorescence staining, and enzyme-linked immunosorbent assay (ELISA). The analyses detailed metabolic alterations and the Toll-like receptor 4 (TLR4) signaling pathway/NOD-like receptor protein 3 (NLRP3) inflammasome in rats' hippocampal region. Furthermore, the activity of the hypothalamic-pituitary adrenal (HPA) axis and gut microbiome was assessed. As a result of treatment, EA significantly improved in the behavioral tests and altered the composition of the gut microbiome through a significant increase in the density of short chain fatty acids (SCFAs) producers mainly including Ruminococcaceae, Phascolarctobacterium, and Akkermansiaceae. EA upregulated the metabolites of the hippocampus mainly containing l-glutamine and gamma-aminobutyric acid (GABA), as well as ZO-1 expression. Whereas the treatment blocked the TLR4/nuclear factor- kappa B (NF-κB) signaling pathways and NLRP3 inflammasomes, along with downregulating the interleukin- (IL-) 1β level. The hyperactivity of the HPA axis was also diminished. In conclusion, EA at ST36 and SP6 attenuated anxiety and depression-like behavior in colitis model rats through their effects on the gut microbiome by modulating the hippocampal inflammatory response and metabolic disorders, as well as the HPA axis. This study provides evidence for clinical application of EA to serve as an adjunctive treatment for IBD-related anxiety and depression.

Comparing the Therapeutic Effects of Crocin, Escitalopram and Co-Administration of Escitalopram and Crocin on Learning and Memory in Rats with Stress-Induced Depression

Background

Depression affects various brain functions. According to previous studies, escitalopram influences brain functions in depression and crocin reduces memory impairments. Therefore, this study aimed to compare the therapeutic effects of using crocin and escitalopram (separately and in combination) on learning and memory in rats with stress-induced depression.

Methods

Fifty-six rats were allocated into seven groups of control, sham, continuous depression, recovery period, daily injections of escitalopram, crocin and escitalopram-crocin during 14 days after inducing depression by stress. Passive avoidance (PA) test was used to assess brain functions.

Results

Latency has significant differences in depression group. Also, it significantly increased in depression-crocin, depression-escitalopram and depression-escitalopram-crocin groups compared to the depression group. The dark stay (DS) time was significantly higher in the depression and depression-recovery groups. However, the DS time significantly decreased in the depression-crocin, depression-escitalopram and depression-escitalopram-crocin groups. Furthermore, the number of entrances to the dark room was significantly lower in depression-crocin and depression-escitalopram-crocin groups compared to the depression one.

Conclusion

Different depression treatments (i.e. crocin, escitalopram and crocin-escitalopram) reduced depression-induced memory deficits. Crocin and escitalopram-crocin, respectively, improved brain functions and locomotor activity more than escitalopram. Comparatively, in subjects with depression, crocin, which is an effective saffron constituent, partially affected the memory deficits better than escitalopram (as a chemical component).

The mechanism of electroacupuncture for depression on basic research: a systematic review

BACKGROUND

Electroacupuncture (EA) is generally accepted as a safe and harmless treatment option for alleviating depression. However, there are several challenges related to the use of EA. Although EA has been shown to be effective in treating depression, the molecular mechanism is unclear.

OBJECTIVE

To reveal the therapeutic effect of EA and its possible mechanism in the treatment of depression.

SEARCH STRATEGY

We performed a systematic search according to PRISMA guidelines. We electronically searched PubMed, Web of Science (WOS), the China National Knowledge Infrastructure (CNKI), Wanfang Data Information Site and the VIP information database for animal studies in English published from the inception of these databases to December 31, 2019.

INCLUSION CRITERIA

Electronic searches of PubMed, WOS, the CNKI, Wanfang and the VIP database were conducted using the following search terms: (depression OR depressive disorder OR antidepressive), (rat OR mouse) AND (acupuncture OR EA).

DATA EXTRACTION AND ANALYSIS

The data were extracted primarily by one author, and a follow-up review was conducted by the other authors.

RESULTS

Twenty-eight articles met the inclusion criteria. The most commonly used method for inducing depression in animal models was 21 days of chronic unpredictable mild stress. For the depression model, the most commonly selected EA frequency was 2 Hz. Among the 28 selected studies, 11 studies observed depression-related behaviors and used them as indicators of EA efficacy. The other 17 studies focused on mechanisms and assessed the indexes that exhibited abnormalities that were known to result from depression and then returned to a normal range after EA treatment. Treatment of depression by EA involves multiple therapeutic mechanisms, including inhibition of HPA axis hyperactivity and inflammation, regulation of neuropeptides and neurotransmitters, modulation of the expression of particular genes, restoration of hippocampal synaptic plasticity, increased expression of BDNF, and regulation of several signaling pathways.

CONCLUSIONS

This review reveals that the mechanisms underlying the effect of acupuncture involve multiple pathways and targets, suggesting that acupuncture is a wholistic treatment for people rather than for diseases. Our findings also explain why acupuncture can treat various disorders in addition to depression.

Applications of Acupuncture Therapy in Modulating the Plasticity of Neurodegenerative Disease and Depression: Do MicroRNA and Neurotrophin BDNF Shed Light on the Underlying Mechanism?

As the global population ages, the incidence of neurodegenerative diseases has risen. Furthermore, it has been suggested that depression, especially in elderly people, may also be an indication of latent neurodegeneration. Stroke, Alzheimer's disease (AD), and Parkinson's disease (PD) are usually accompanied by depression. The urgent challenge is further enforced by psychiatric comorbid conditions, particularly the feeling of despair in these patients. Fortunately, as our understanding of the neurobiological substrates of maladies affecting the central nervous system (CNS) has increased, more therapeutic options and novel potential biological mechanisms have been presented: (1) Neurodegenerative diseases share some similarities in their pathological characteristics, including changes in neuron structure or function and neuronal plasticity. (2) MicroRNAs (miRNAs) are small noncoding RNAs that contribute to the pathogenesis of diverse neurological disease. (3) One ubiquitous neurotrophin, brain-derived neurotrophic factor (BDNF), is crucial for the development of the nervous system. Accumulating data have indicated that miRNAs not only are related to BDNF regulation but also can directly bind with the 3'-UTR of BDNF to regulate BDNF and participate in neuroplasticity. In this short review, we present evidence of shared biological substrates among stroke, AD, PD, and depression and summarize the possible influencing mechanisms of acupuncture on the neuroplasticity of these diseases. We discuss neuroplasticity underscored by the roles of miRNAs and BDNF, which might further reveal the potential biological mechanism of neurodegenerative diseases and depression by acupuncture.

Transcutaneous Auricular Vagus Nerve Stimulation at 20 Hz Improves Depression-Like Behaviors and Down-Regulates the Hyperactivity of HPA Axis in Chronic Unpredictable Mild Stress Model Rats

Transcutaneous auricular vagus nerve stimulation (taVNS) has gained growing interest as a non-invasive and non-pharmacologic treatment option in various neurological and psychiatric disorders. Animal experiments and clinical trials confirm that taVNS at the auricular concha region has beneficial effects on depression. However, stimulation frequencies are selected empirically, and there is no evidence showing that any frequency is superior to the others. This study explores antidepressant-like effects of three frequencies of taVNS on rats subjected to chronic unpredictable mild stress (CUMS). Sprague-Dawley rats were randomly divided into five groups, i.e., the control, CUMS, 5 Hz-taVNS, 20 Hz-taVNS, and 100 Hz-taVNS groups. The three different frequencies were administered during the 30-min taVNS procedure once a day for 28 consecutive days. Rats exposed to CUMS showed signs of depression-like behaviors, including reduction in sucrose preference and increased immobility time in forced swimming and open field tests as well as significant dysfunction of the hypothalamic-pituitary-adrenal (HPA) axis as detected by plasma corticosterone and adrenocorticotropic hormone concentration. The 28 days’ taVNS sessions with three frequencies elicited quite different consequences. Although 20 Hz taVNS significantly reversed the depression-like behaviors and downregulated the hyperactivity of the HPA axis, neither 5 nor 100 Hz showed any antidepressant-like effect on CUMS-induced rat behavior. Based on these results, we propose that, out of the three frequencies for taVNS intervention on depression, 20 Hz may be the optimized frequency to have a better modulation effect on HPA axis function by activating the auricular vagus nerve.

Electroacupuncture Improves Antidepressant Effects in CUMS Rats by Protecting Hippocampal Synapse and Mitochondrion: An Ultrastructural and iTRAQ Proteomic Study

Electroacupuncture (EA) is considered a complementary therapy for depression. Trials also found that EA has additive benefits when combined with medication compared with medication alone. It is revealed that EA restores altered hippocampal synaptic plasticity in depressed brain. But precise molecular mechanism is poorly understood. Here, we evaluated the therapeutic effects of EA and EA combined with selective serotonin reuptake inhibitor (SSRI) on depressed (CUMS) rats. Then a new proteomics approach, isobaric tag for relative and absolute quantitation (iTRAQ), was used to explore the differential expressed synaptic protein in hippocampus between CUMS and EA-treated rats to identify the possible target molecular mechanism of its effects. We found that EA had additive benefit against depressive behaviors when combined with SSRI. Ultrastructure study on neuron showed significant change in postsynapse density (PSD) and mitochondrion. Through iTRAQ, it is found that synaptic and mitochondrial proteins were significantly changed after EA, consisting with ultrastructure study results. These findings suggest that EA improves antidepressant performance in depressed rats through protecting synaptic and mitochondrial functions in hippocampus.

A New Method for Inducing a Depression-Like Behavior in Rats

Contagious depression is a phenomenon that is yet to be fully recognized and this stems from insufficient material on the subject. At the moment, there is no existing format for studying the mechanism of action, prevention, containment, and treatment of contagious depression. The purpose of this study, therefore, was to establish the first animal model of contagious depression. Healthy rats can contract depressive behaviors if exposed to depressed rats. Depression is induced in rats by subjecting them to several manipulations of chronic unpredictable stress (CUS) over 5 weeks, as described in the protocol. A successful sucrose preference test confirmed the development of depression in the rats. The CUS-exposed rats were then caged with naïve rats from the contagion group (1 naïve rat/2 depressed rats in a cage) for an additional 5 weeks. 30 social groups were created from the combination of CUS-exposed rats and naïve rats. This proposed depression-contagion protocol in animals consists mainly of cohabiting CUS-exposed and healthy rats for 5 weeks. To ensure that this method works, a series of tests are carried out - first, the sucrose preference test upon inducing depression to rats, then, the sucrose preference test, alongside the open field and forced-swim tests at the end of the cohabitation period. Throughout the experiment, rats are given tags and are always returned to their cages after each test. A few limitations to this method are the weak differences recorded between the experimental and control groups in the sucrose preference test and the irreversible traumatic outcome of the forced swim test. These may be worth considering for suitability before any future application of the protocol. Nonetheless, following the experiment, naïve rats developed contagion depression after 5 weeks of sharing the same cage with the CUS-exposed rats.

Acupuncture for behavioral changes of experimental depressive disorder: a systematic review and meta-analysis

Acupuncture is considered to be a promising alternative therapy for depression. Nevertheless, up to now, it remains controversial on the effects exerted by acupuncture on behavioral changes in depression models. Consequently, it’s necessary to develop a systematic review and meta-analysis to assess the effect of acupuncture for model rats of depression. Ultimately, 90 studies involving 1861 models were identified. Behavioral indicators including the number of crossings (NC) and the number of rearings (NR) in open field test (OFT), the capacity of sucrose intake (CSI) and the rate of sucrose intake (RSI) in sucrose intake test (SIT), final weight (FW) and gain weight (GW) were employed as main outcomes in depression model rats. The pooled results showed that acupuncture had not less effect than western medicine on improving NC, NR, FW, GW, RSI (P > 0.05). However, the CSI improvement was poorer compared with west medicine (P < 0.05). In conclusion, acupuncture has not less effect on behavior changes than western medicine, including improving NC, NR, RSI, FW and GW in depression models.

Electroacupuncture Restores 5-HT System Deficit in Chronic Mild Stress-Induced Depressed Rats

Objective. The current study is designed to investigate the antidepressant efficacy of electroacupuncture (EA) treatment by evaluating its effect on the synthesis, metabolism, reuptake, and receptors of 5-hydroxytryptamine (5-HT), so as to clarify the molecular mechanisms of EA for antidepression. Materials and Methods. Solitary combined with the chronic unpredictable mild stress (CUMS) was used to establish the rat model with depression. The depressed rats were supplied with EA treatment for 4 weeks, and the behavior change and the following indices including 5-HT, 5-hydroxyindoleacetic acid (5-HIAA), monoamine oxidase A (MAO-A), tryptophan hydroxylase (TPH), 5-HT transporter (SERT), 5-HT1A, and 5-HT2A in hippocampus and prefrontal cortex were examined. Results. EA treatment significantly improved the behavior of rats and increased 5-HT level in hippocampus of depressed rats. Similarly, EA treatment could significantly increase protein and mRNA expression of TPH and 5-HT1A during 5-HT synthesis process in hippocampus of depressed rats. However, EA treatment had no effect on the activity of MAO-A and the expression of SERT protein and mRNA. Conclusion. Antidepressant efficacy of EA treatment can be accomplished through enhancing 5-HT synthesis, upregulating 5-HT1A level, and improving 5-HT content in brain and synaptic gaps.

Electroacupuncture Alleviates Depressive-Like Symptoms and Modulates BDNF Signaling in 6-Hydroxydopamine Rats

Previous studies have identified the beneficial effects of electroacupuncture (EA) on motor behaviors in Parkinson's disease (PD). However, the role and potential mechanisms of EA in PD-associated depression remain unclear. In the present study, a rat model of PD with unilateral 6-hydroxydopamine (6-OHDA) lesions in the medial forebrain bundle was treated using EA for 4 weeks. We found that 100 Hz EA improved several motor phenotypes. In addition, tyrosine hydroxylase (TH) immunohistochemical analysis showed that EA had a minimal impact on the TH-positive profiles of the ipsilateral ventral tegmental area. Compared with the 6-OHDA group, long-term EA stimulation significantly increased sucrose solution consumption and decreased immobility time in the forced swim test. EA treatment did not alter dopamine, norepinephrine, and serotonin levels in the striatum and hippocampus. Noticeably, EA treatment reversed the 6-OHDA-induced abnormal expression of brain-derived neurotrophic factor (BDNF) and tropomyosin-related kinase B (TrkB) in the midbrain and hippocampus. These results demonstrate that EA at 100-Hz possesses the ability to improve depressive-like symptoms in PD rats, which is, at least in part, due to the distinct effect of EA on the mesostriatal and mesocorticolimbic dopaminergic pathways. Moreover, BDNF seems to participate in the effect of EA in PD.

BDNF and COX-2 participate in anti-depressive mechanisms of catalpol in rats undergoing chronic unpredictable mild stress

Catalpol, a major compound in Rehmannia glutinosa with both medicinal and nutritional values, has been previously confirmed to shorten the duration of immobility in mice exposed to tail suspension and forced swimming tests. This study attempted to examine the anti-depressive mechanisms of catalpol in rats undergoing chronic unpredictable mild stress (CUMS) by involving brain-derived neurotrophic factor (BDNF) and cyclooxygenase-2 (COX-2). CUMS-exposed rats were given catalpol daily (5, 10, and 20mg/kg, ig) or a reference drug, fluoxetine hydrochloride (FH, 10mg/kg, ig), at 5 weeks after starting the CUMS procedure. Sucrose preference test was performed to observe depression-like behavior, and serum and brain tissues were used for neurochemical and fluorescent quantitative reverse transcription PCR analysis. CUMS induced depression-like behavior, whereas catalpol and FH administration attenuated this symptom. Moreover, CUMS caused excessively elevated levels of serum corticosterone, an index of hypothalamic-pituitary-adrenal (HPA) axis hyperactivation, in a manner attenuated by catalpol and FH administration. Catalpol administration also further decreased BDNF activities, downregulated the mRNA expression of BDNF and tropomyosin-related kinase B (TrkB), and reversed the excessive elevation in the activities and mRNA expression levels of COX-2 and prostaglandin E2 (PGE2) in the hippocampus and frontal cortex of rats undergoing CUMS. Results indicate that catalpol can ameliorate CUMS-induced depression-like behavior, and suggest its mechanisms may partially be ascribed to restoring HPA axis dysfunctions, upregulating BDNF expression and its cognate receptor TrkB, and downregulating COX-2 expression, thereby reducing PGE2 levels in the brain.

Regulation of Neurotrophin-3 and Interleukin-1β and Inhibition of Spinal Glial Activation Contribute to the Analgesic Effect of Electroacupuncture in Chronic Neuropathic Pain States of Rats

Growing evidence indicates that neurotrophin-3, interleukin-1β, and spinal glia are involved in neuropathic pain derived from dorsal root ganglia to spinal cord. Electroacupuncture is widely accepted to treat chronic pain, but the precise mechanism underlying the analgesic effect of EA has not been fully demonstrated. In this study, the mechanical withdrawal threshold and thermal withdrawal latency were recorded. We used immunofluorescence and western blots methods to investigate the effect of EA on the expression of NT-3 and IL-1β in DRG and spinal cord of CCI rats; we also examined the expression of spinal GFAP and OX-42 in spinal cord. In present study, the MWT and TWL of CCI group rats were lower than those in the Sham CCI group rats, but EA treatment increased the pain thresholds. Furtherly, we found that EA upregulates the expression of NT-3 in DRG and spinal cord of CCI rats, while EA downregulates the expression of IL-1β. Additionally, immunofluorescence exhibited that CCI-induced activation of microglia and astrocytes was inhibited significantly by EA treatment. These results demonstrated that the analgesic effect of EA may be achieved through promoting the neural protection of NT-3 as well as the inhibition of IL-1β production and spinal glial activity.

Behavioral effects of nicotinic antagonist mecamylamine in a rat model of depression: prefrontal cortex level of BDNF protein and monoaminergic neurotransmitters

Several studies have pointed to the nicotinic acetylcholine receptor (nAChR) antagonists, such as mecamylamine (MEC), as a potential therapeutic target for the treatment of depression. The present study evaluated the behavioral and neurochemical effects of chronic administration of MEC (1, 2, and 4 mg/kg/day, intraperitoneally (i.p.)) in Wistar rats exposed to chronic restraint stress (CRS, 4 h × 6 W). MEC prevented CRS-induced depressive-like behavior via increasing sucrose preference, body weight, and forced swim test (FST) struggling and swimming while reducing immobility in FST and hypothalamic-pituitary-adrenal (HPA) axis hyperactivity (adrenal gland weight and serum corticosterone). At the same time, MEC amended CRS-induced anxiety as indicated by decreasing central zone duration in open field test and increasing active interaction duration. Additionally, MEC modulated the prefrontal cortex (PFC) level of brain-derived neurotrophic factor (BDNF), 5-hydroxy tryptamine (5-HT), and norepinephrine (NE). In conclusion, the present data suggest that MEC possesses antidepressant and anxiolytic-like activities in rats exposed to CRS. These behavioral effects may be in part mediated by reducing HPA axis hyperactivity and increasing PFC level of BDNF and monoamines. Accordingly, these findings further support the hypothesis that nAChRs blockade might afford a novel promising strategy for pharmacotherapy of depression.

Establishment of an animal model of depression contagion

BACKGROUND

Depression is a common and important cause of morbidity, and results in a significant economic burden. Recent human studies have demonstrated that that depression is contagious, and depression in family and friends might cumulatively increase the likelihood that a person will exhibit depressive behaviors. The mechanisms underlying contagion depression are poorly understood, and there are currently no animal models for this condition.

METHODS

Rats were divided into 3 groups: depression group, contagion group, and control group. After induction of depression by 5 weeks of chronic unpredictable stress, rats from the contagion group were housed with the depressed rats (1 naïve rat with 2 depressed rats) for 5 weeks. Rats were then subjected to sucrose preference, open field, and forced swim tests.

RESULTS

The sucrose preference was significantly reduced in the depressed rats (p<0.01) and contagion depression rats (p<0.01). Climbing time during forced swim test was reduced in the depression and contagion depression groups (p<0.001), whereas immobility time was significantly prolonged in only the depression group (p<0.001). Rats in both the depression (p<0.05) and depression contagion group (p<0.005) had decreased total travel distance and decreased mean velocity in the open field test, whereas the time spent in the central part was significantly shorter in only the depression group (p<0.001).

CONCLUSIONS

In this study, for the first time we demonstrated depression contagion in an animal model. A reliable animal model may help better understand the underlying mechanisms of contagion depression, and may allow for future investigations of the studying therapeutic modalities.

Chronic unpredictable mild stress impairs erythrocyte immune function and changes T-lymphocyte subsets in a rat model of stress-induced depression

Stress has been shown to suppress immune function and increase susceptibility to inflammatory and psychiatric diseases. This study sought to investigate the changes in erythrocyte immune functions and T-lymphocyte subsets and to explore the mechanism implicated in the process of stress-induced depression by employing a rat depression model induced by chronic unpredictable mild stress (CUMS). The body weights and behavioral changes of the rats were recorded, and plasma corticosterone levels were determined by radioimmunoassay. Erythrocyte immune function and T-lymphocytes subsets were respectively measured by the method of yeast rosette and flow cytometry at different time intervals, and their relationship was analyzed. Results indicated that a reduction was observed in the following: the rats' crossing and rearing movement times, the volume of sucrose intake and the preference for sucrose in the depression model group. Plasma corticosterone levels were elevated; the rate of E-C3bR decreased, and E-IC was increased. Some alterations in the percentage of T-lymphocytes and IL-2 appeared in the depression model group and some relationships existed between these parameters. Collectively, these findings disclose that long-time stress could induce changes in rat behavior and activities through an effect on erythrocyte immune functions and T-lymphocyte subsets.

Electroacupuncture upregulates ERK signaling pathways and promotes adult hippocampal neural progenitors proliferation in a rat model of depression

Background

In this study, we investigate the proliferation of adult neural stem cells (NSCs) in a chronic unpredictable stress (CUS) rat model of depression, the effects of electroacupunture (EA) on depressive-like symptoms and the corresponding signaling pathways.

Methods

SD rats were subjected to 4 weeks of CUS to induce depressive-like behaviors. EA was performed at the Du-20 (Bai-Hui) and GB-34 (Yang-Ling-Quan) acupoints. Rats were injected with BrdU and the brains were cut into sections. Double-labeling with BrdU/Sox2 and p-ERK/Nestin was performed to demonstrate the in vivo proliferation of adult NSCs in hippocampus and ERK activation in NSCs. Hippocampal microdialysates of different groups were collected to observe the in vitro effects on NSCs.

Results

After 8 treatments, EA generated a clear antidepressant effect on the stressed rats and promoted the NSC proliferation. ERK activation might be involved in the antidepressant-like effects of EA treatment. Hippocampal microdialysates from EA-treated stressed rats influenced NSCs to form larger neural spheres and exhibit higher p-ERK level in vitro, compared to the untreated stressed rats. Meanwhile, the antidepressant-like effects of EA involved contribution from both acupoint specificity and electrical stimulus.

Conclusions

EA might interfere with the hippocampal microenvironment and enhance the activation of ERK signaling pathways. This could mediate, at least in part, the beneficial effects of EA on NSC proliferation and depressive-like behaviors.

Acupuncture Activates ERK-CREB Pathway in Rats Exposed to Chronic Unpredictable Mild Stress

Extracellular signal-regulated kinase (ERK)-cAMP response element binding protein (CREB) signal pathway has been implicated in the pathogenesis of depression. There is growing evidence that acupuncture in traditional Chinese medicine has antidepressant-like effect. However, the effect of acupuncture on ERK-CREB pathway remains unknown. In our study, the antidepressant-like effect of acupuncture treatment was measured by sucrose intake test and open field test in rats exposed to chronic unpredictable mild stress (CUMS) for 4 weeks. The protein levels of ERK1/2, CREB, phosphorylated ERK1/2 (p-ERK1/2), and phosphorylated CREB (p-CREB) in the hippocampus (HP) and prefrontal cortex (PFC) were examined by Western blot analysis. Our results showed that CUMS rats exhibited the reduction in behavioral activities, whereas acupuncture stimulation at acupoints Baihui (Du20) and Neiguan (PC6) reversed the behavioral deficit. In addition, exposure to CUMS resulted in the decrease of p-ERK1/2 and p-CREB in the HP and PFC. Acupuncture increased the ratio of p-ERK1/2 to ERK1/2 and the ratio of p-CREB to CREB in the HP and PFC. Our study suggested that one potential way, by which acupuncture had antidepressant-like effect, might be mediated by activating the ERK-CREB pathway in the brain.