Cannabinoid type 2 receptors play a crucial role in social defeat-induced depression.

BACKGROUND: The endocannabinoid system plays a crucial role in regulating mood, but the specific involvement of cannabinoid receptor type 2 (CB2R) in depression remains poorly understood. Similarly, the mechanisms by which electroacupuncture (EA) provides therapeutic benefits for depression are not clearly defined. This research aims to explore the function of CB2R in depression and examine if the therapeutic effects of EA are associated with the hippocampal CB2R system. METHODS: Mice experiencing social defeat stress (SDS) were used to model depression and anxiety behaviors. We quantified hippocampal CB2R and N-arachidonoylethanolamide (AEA) levels. The efficacy of a CB2R agonist, JWH133, in mitigating SDS-induced behaviors was evaluated. Additionally, EA's impact on CB2R and AEA was assessed, along with the influence of CB2R antagonist AM630 on EA's antidepressant effects. RESULTS: SDS led to depressive and anxiety-like behaviors, with corresponding decreases in hippocampal CB2R and AEA. Treatment with JWH133 ameliorated these behaviors. EA treatment resulted in increased CB2R and AEA levels, while AM630 blocked these antidepressant effects. LIMITATIONS: The study mainly focused on the SDS model, which may not entirely reflect other depression models. Besides, further investigation is needed to understand the precise mechanisms by which CB2R and AEA contribute to EA's effects. CONCLUSIONS: The study suggests hippocampal downregulation of CB2R and AEA contributes to depression. Upregulation of CB2R and AEA in response to EA suggests their involvement in EA's antidepressant effects. These findings provide insights into the role of the hippocampal CB2R system in depression and the potential mechanisms underlying EA's therapeutic effects.

The neuroprotective effects of GPR55 against hippocampal neuroinflammation and impaired adult neurogenesis in CSDS mice.

Depression is one of the most prevalent mental illnesses in the world today, and the onset of depression is usually accompanied by neuroinflammation and impaired adult neurogenesis. As a new potential member of the endocannabinoid (eCB) system, G protein coupled receptor 55 (GPR55) has been associated with mood regulation. However, the role of GPR55 in the pathophysiology of depression remains poorly understood. Thus, a 10-day chronic social defeat stress (CSDS) paradigm was utilized as an animal model of depression to explore the potential role of GPR55 in depression. After CSDS, the protein level of GPR55 decreased significantly, but the mRNA expression did not change significantly, highlighting that although the GPR55 protein was involved in the progression of the depression- and anxiety-like phenotypes, its mRNA was not. Additionally, depression- and anxiety-like behaviors were also accompanied by neuroinflammation and impaired adult neurogenesis in the hippocampus. Interestingly, O-1602, a GPR55 agonist, remarkably prevented the development of depression- and anxiety-like behaviors as well as hippocampal neuroinflammation and neurogenesis deficits induced by CSDS. However, after electroacupuncture (EA) alleviated depression- and anxiety-like behaviors induced by CSDS, treatment with a GPR55 antagonist (CID16020046) reversed this effect. Our research demonstrated that downregulation of GPR55 expression in the hippocampus might mediate CSDS-induced depression- and anxiety-like phenotypes, and activation and upregulation of GPR55, which might be correlated with its anti-inflammatory and subsequent neuroprotective effects, could be a potential treatment for depression.

The antidepressant and anxiolytic effect of GPER on translocator protein (TSPO) via protein kinase a (PKA) signaling in menopausal female rats.

Postmenopausal depression is mainly caused by the deprivation of ovarian hormones during menopausal transition, it is of great importance to study on the treatment that could effectively relieve symptoms of menopausal depression with fewer side effects. Activation of G-protein-coupled estrogen receptor (GPER) has long been reported to facilitate neuronal plasticity and improve cognition in animals. Meanwhile, it could participate in regulation of intracellular signaling pathways through the characteristic of GPER, ameliorate intracellular mitochondrial function and oxidative stress. However, the impact of GPER on regulating estrogen deprived-depressant and anxious behaviors is still largely unknown. Here we used the ovariectomized female rats to imitate the condition of menopause. Owing to the lateral ventricle administration of G-1 which specifically react with GPER receptor intracerebrally, Ovariectomized (OVX) female rats showed depressive- or anxiety-like phenotypes with attenuated mitochondrial function. In addition, G-1 facilitated PKA activation, which further accelerated TSPO phosphorylation and alleviated menopausal depression- and anxiety-like behaviors. Moreover, PKA inhibitor PKI could partially antagonized the anti-anxiety and anti-depression effects of G-1. Taken together, we concluded that GPER activation might exhibit antidepressant and anxiolytic effect by elevating TSPO phosphorylation via protein kinase A signaling and rescuing the redox status in menopausal female rats.

[Electroacupuncture promotes regeneration and repair of myelin sheath of corpus callosum in demyelination mice].

OBJECTIVE: To explore the mechanism of electroacupuncture (EA) in accelerating the aggregation of microglia and promoting the remyelination at the location of demyelination. METHODS: C57BL/6 mice were randomly divided into 4 groups: normal, control, model (LPC) and LPC＋EA. The demyelination model was established by microinjection of Lysolecithin (LPC, 1 µL) into the left corpus callosum. EA (2 Hz/15 Hz, 2－4 mA) was applied to "Baihui"(GV20)and "Zhiyang"(GV9)for 30 min，once daily for 3 days, then, once every other day for 18 days. Immuno-fluorescence staining was used to observe the expression of myelin basic protein (MBP) and Axl tyrosine kinase receptor (Axl), Iba1 and numbers of Olig2-positive oligodendrocytes in the corpus callosum. Western blot was employed to detect the expression of MBP in the corpus callosum, and Oil Red O staining was used to observe changes of number of myelin pieces. RESULTS: Following modeling, the expression levels of MBP on day 5 and 10 after modeling were significantly decreased (P<0.05, P<0.01), Iba1 expression and Olig2-positive oligodendrocyte numbers on day 10 apparently increased (P<0.001, P<0.01). On day 21 after modeling, the levels of the above mentioned indexes returned to normal. After EA intervention, the levels of MBP expression on day 5 and 10, Axl, Iba1 protein expression and Olig2-positive oligodendrocyte numbers on day 5 were markedly increased (P<0.001，P<0.01，P<0.05), while Iba1 expression on day 10 was considerably decreased in comparison with the model group (P<0.01)．Oil Red O staining showed that on day 5 after modeling, the number of red lipid droplets were obviously increased in the corpus callosum tissue on the injection side, and apparently reduced in the EA group, suggesting a clearance of the accumulated myelin fragments by EA. CONCLUSION: EA intervention may reduce myelin debris and promote the aggregation of microglial cells and oligodendrocytes to the injured site, accelerate the myelin regeneration and up-regulate the expression of MBP and Axl of corpus callosum in demyelination mice.

miR-124/VAMP3 is a novel therapeutic target for mitigation of surgical trauma-induced microglial activation.

Activation of microglia and the subsequently elevated inflammatory cytokine release in the brain during surgery predispose individuals to cognitive dysfunction, also known as postoperative cognitive dysfunction (POCD). miR-124 is one of the most abundant microRNAs in the brain that regulates microglial function. Elucidating the role of miR-124 in microglial activation in the context of surgery may therefore promote understanding of as well as therapeutic development for post-surgical disorders involving microglial activation. The downstream targets of miR-124 were investigated using bioinformatic screening and dual-luciferase reporter assay validation, and vesicle-associated membrane protein 3 (VAMP3) was identified as a potential target. The kinetics of miR-124/VAMP3 expression was first examined in vitro in microglial cells (primary microglia and BV2 microglial cells) following lipopolysaccharide (LPS) stimulation. LPS induced a time-dependent decrease of miR-124 and upregulated the expression of VAMP3. Manipulating miR-124/VAMP3 expression by using miR-124 mimics or VAMP3-specific siRNA in LPS-stimulated BV2 microglial cells inhibited BV2 microglial activation-associated inflammatory cytokine release. To further examine the role of miR-124/VAMP3 in a surgical setting, we employed a rat surgical trauma model. Significant microglial activation and altered miR-124/VAMP3 expression were observed following surgical trauma. We also altered miR-124/VAMP3 expression in the rat surgical trauma model by administration of exogenous miR-124 and by using electroacupuncture, which is a clinically applicable treatment that modulates microglial function and minimizes postoperative disorders. We determined that electroacupuncture treatment specifically increases the expression of miR-124 in the hypothalamus and hippocampus. Increased miR-124 expression with a concomitant decrease in VAMP3 expression resulted in decreased inflammatory cytokine release related to microglial activation post-surgery. Our study indicates that miR-124/VAMP3 is involved in surgery-induced microglial activation and that targeting miR-124/VAMP3 could be a potential therapeutic strategy for postoperative disorders involving microglial activation.

The protective effects of Ghrelin/GHSR on hippocampal neurogenesis in CUMS mice.

Ghrelin is an orexigenic hormone that also plays an important role in mood disorders. Our previous studies demonstrated that ghrelin administration could protect against depression-like behaviors of chronic unpredictable mild stress (CUMS) in rodents. However, the mechanism related to the effect of ghrelin on CUMS mice has yet to be revealed. This article shows that ghrelin (5 nmol/kg/day for 2 weeks, i.p.) decreased depression-like behaviors induced by CUMS and increased hippocampal integrity (neurogenesis and spine density) measured via Ki67, 5-bromo-2-deoxyuridine (BrdU), doublecortin (DCX) labeling and Golgi-cox staining, which were decreased under CUMS. The behavioral phenotypes of Growth hormone secretagogue receptor (Ghsr)-null and wild type (WT) mice were evaluated under no stress condition and after CUMS exposure to determine the effect of Ghsr knockout on the behavioral phenotypes and stress susceptibility of mice. Ghsr-null mice exhibited depression-like behaviors under no stress condition. CUMS induced similar depression- and anxiety-like behavioral manifestations in both Ghsr-null and WT mice. A similar pattern of behavioral changes was observed after hippocampal GHSR knockdown. Additionally, both Ghsr knockout as well as CUMS exhibited deleterious effects on neurogenesis and spine density in the dentate gyrus (DG). Besides, CCK8 assay and 5-Ethynyl-2'-deoxyuridine (EdU) incorporation assay showed that ghrelin has a proliferative effect on primary cultured hippocampal neural stem cells (NSCs) and this proliferation was blocked by D-Lys3-GHRP-6 (DLS, the antagonist of GHSR, 100 µM) pretreatment. Ghrelin-induced proliferation is associated with the inhibition of G1 arrest, and this inhibition was blocked by LY294002 (specific inhibitor of PI3K, 20 µM). Furthermore, the in vivo data displayed that LY294002 (50 nmol, i.c.v.) can significantly block the antidepressant-like action of exogenous ghrelin treatment. All these results suggest that ghrelin/GHSR signaling maintains the integrity of hippocampus and has an inherent neuroprotective effect whether facing stress or not.

Ghrelin exhibited antidepressant and anxiolytic effect via the p38-MAPK signaling pathway in hippocampus.

Ghrelin, a peptide derived from stomach, is an endogenous ligand for growth hormone secretagogue receptor (GHSR). So far, the exact role of ghrelin in depression and anxiety is still being debated. The p38 mitogen-activated protein kinase (p38-MAPK) is known to be activated in response to various stress stimuli. Thus, we hypothesize that ghrelin has an antidepressant effect, to which the p38-MAPK signaling pathway significantly contributes. To test this hypothesis, chronic social defeat stress (CSDS) was used as a model of depression. We employed the adeno-associated virus-mediated siRNA approach to down-regulate GHSR expression in the hippocampus of mice in vivo. Both ghrelin and the p38 inhibitor, SB203580, were administered to identify the effect of ghrelin on depressive-like behavior of stressed mice and to better assess the role of the p38-MAPK signaling pathway in this process. We found that CSDS activated the endogenous ghrelin-GHSR in hippocampal neurons, which possibly resulted in opposing the formation of depression- and anxiety-like behaviors in mice. Furthermore, the p38-MAPK signaling pathway had an important role in the antidepressant effect of ghrelin. Therefore, we conclude that ghrelin may reduce CSDS-induced depression- and anxiety-like behaviors via inhibiting the p38-MAPK signaling pathway in hippocampal neurons of mice.

Prevention and Treatment for Chemotherapy-Induced Peripheral Neuropathy: Therapies Based on CIPN Mechanisms.

BACKGROUND: Chemotherapy-induced peripheral neuropathy (CIPN) is a progressive, enduring, and often irreversible adverse effect of many antineoplastic agents, among which sensory abnormities are common and the most suffering issues. The pathogenesis of CIPN has not been completely understood, and strategies for CIPN prevention and treatment are still open problems for medicine. OBJECTIVES: The objective of this paper is to review the mechanism-based therapies against sensory abnormities in CIPN. METHODS: This is a literature review to describe the uncovered mechanisms underlying CIPN and to provide a summary of mechanism-based therapies for CIPN based on the evidence from both animal and clinical studies. RESULTS: An abundance of compounds has been developed to prevent or treat CIPN by blocking ion channels, targeting inflammatory cytokines and combating oxidative stress. Agents such as glutathione, mangafodipir and duloxetine are expected to be effective for CIPN intervention, while Ca/Mg infusion and venlafaxine, tricyclic antidepressants, and gabapentin display limited efficacy for preventing and alleviating CIPN. And the utilization of erythropoietin, menthol and amifostine needs to be cautious regarding to their side effects. CONCLUSIONS: Multiple drugs have been used and studied for decades, their effect against CIPN are still controversial according to different antineoplastic agents due to the diverse manifestations among different antineoplastic agents and complex drug-drug interactions. In addition, novel therapies or drugs that have proven to be effective in animals require further investigation, and it will take time to confirm their efficacy and safety.

Electro-Acupuncture Alleviates Chronic Unpredictable Stress-Induced Depressive- and Anxiety-Like Behavior and Hippocampal Neuroinflammation in Rat Model of Depression.

Depression is the second leading cause of disability worldwide. The effects of clinical depression may be mediated by neuroinflammation such as activation of microglia and high levels of proinflammatory cytokines in certain brain areas. Traditional Chinese medicine techniques such as electro-acupuncture (EA) are used extensively in Asia to treat mental health disorders. However, EA has not been rigorously studied in treatment of depression. This study was designed to assess the effectiveness of EA on depressive-like behavior and explore the role of hippocampal neuroinflammation in the potential antidepressant effect of EA. In this study, we used six chronic unpredictable stressors daily in a random sequence for 10 weeks. EA were performed on "Bai-Hui" (Du-20) (+) and "Yang-Ling-Quan" (GB-34, the right side; -) acupoints by an EA apparatus (HANS Electronic Apparatus, LH202H, 2/100 Hz, 0.3 mA) for 30 min once every other day for last 4 weeks. The behavior tests including open field test and forced swimming test, which are widely used to assess depressive and anxiety-like behavior were performed on the Monday and Tuesday of the eleventh week. The results showed that 10 week of chronic unpredictable stress (CUS) caused behavioral deficits in rats and neuroinflammation in hippocampus, such as increased expression of NLRP3 inflammasome components, upregulated mRNA level of IL-1ß and the protein level of IL-1ß mature form (p17) and activation of microglia. Moreover, 4 weeks of EA treatment significantly attenuated behavioral deficits caused by CUS. EA's antidepressant effect was accompanied by markedly decreased expression of certain NLRP3 inflammasome components and matured IL-1ß. Meanwhile, EA treatment can significantly reverse CUS-induced increases in P2X7 receptor, Iba-1, IL-18, TNFα and IL-6 expression and decreases in GFAP expression. In conclusion, EA exhibited the antidepressant effect and alleviated the hippocampal neuroinflammation. These findings may provide insight into the role of hippocampal neuroinflammation in the antidepressant effect of EA.

Triggering receptor expressed on myeloid cells 2 (TREM2) dependent microglial activation promotes cisplatin-induced peripheral neuropathy in mice.

Chemotherapy-induced peripheral neuropathy (CIPN) is a common adverse side effect of many antineoplastic agents. Patients treated with chemotherapy often report pain and paresthesias in a "glove-and-stocking" distribution. Diverse mechanisms contribute to the development and maintenance of CIPN. However, the role of spinal microglia in CIPN is not completely understood. In this study, cisplatin-treated mice displayed persistent mechanical allodynia, sensory deficits and decreased density of intraepidermal nerve fibers (IENFs). In the spinal cord, activation of microglia, but not astrocyte, was persistently observed until week five after the first cisplatin injection. Additionally, mRNA levels of inflammation related molecules including IL-1ß, IL-6, tumor necrosis factor (TNF)-α, inducible nitric oxide synthase (iNOS) and CD16, were increased after cisplatin treatment. Intraperitoneal (i.p.) or intrathecal (i.t.) injection with minocycline both alleviated cisplatin-induced mechanical allodynia and sensory deficits, and prevented IENFs loss. Furthermore, cisplatin enhanced triggering receptor expressed on myeloid cells 2 (TREM2) /DNAX-activating protein of 12 kDa (DAP12) signaling in the spinal cord microglia. The blockage of TREM2 by i.t. injecting anti-TREM2 neutralizing antibody significantly attenuated cisplatin-induced mechanical allodynia, sensory deficits and IENFs loss. Meanwhile, anti-TREM2 neutralizing antibody prominently suppressed the spinal IL-6, TNF-α, iNOS and CD16 mRNA level, but it dramatically up-regulated the anti-inflammatory cytokines IL-4 and IL-10. The data demonstrated that cisplatin triggered persistent activation of spinal cord microglia through strengthening TREM2/DAP12 signaling, which further resulted in CIPN. Functional blockage of TREM2 or inhibition of microglia both benefited for cisplatin-induced peripheral neuropathy. Microglial TREM2/DAP12 may serve as a potential target for CIPN intervention.

Differential GR Expression and Translocation in the Hippocampus Mediates Susceptibility vs. Resilience to Chronic Social Defeat Stress.

While social stress exposure is a common risk factor for affective disorders, most individuals exposed to it can maintain normal physical and psychological functioning. However, factors that determine susceptibility vs. resilience to social stress remain unclear. Here, the resident-intruder model of social defeat was used as a social stressor in male C57BL/6J mice to investigate the difference between susceptibility and resilience. As depression is often characterized by hyperactivity of the hypothalamic-pituitary-adrenal (HPA) axis, we conducted the present study to further investigate the individual differences in the HPA axis response and glucocorticoid receptor (GR) protein expression and translocation between susceptible mice and resilient mice. We found that hypercortisolemia, induced by social defeat stress occurred in susceptible mice, but not in resilient mice. Moreover, susceptible mice exhibited significantly less GR protein expression and nuclear translocation in the hippocampus than resilient mice. Treatment with escitalopram could decrease the serum corticosterone (CORT), increase GR protein expression as well as nuclear translocation in the hippocampus and ultimately reverse social withdrawal behaviors in susceptible mice. These results indicate that the up-regulation of GR and the enhancement of GR nuclear translocation in the hippocampus play an important role in resilience to chronic social defeat stress.

Ghrelin alleviates anxiety- and depression-like behaviors induced by chronic unpredictable mild stress in rodents.

As a regulator of food intake, ghrelin also plays a key role in mood disorders. Previous studies reported that acute ghrelin administration defends against depressive symptoms of chronic stress. However, the effects of long-term ghrelin on rodents under chronic stress hasn't been revealed. In this study, we found chronic peripheral administration of ghrelin (5nmol/kg/day for 2 weeks, i.p.) could alleviate anxiety- and depression-like behaviors induced by chronic unpredictable mild stress (CUMS). The depression-like behaviors were assessed by the forced swimming test (FST), and anxiety-like behaviors were assessed by the open field test (OFT) and the elevated plus maze test (EPM). Meanwhile, we observed that peripheral acylated ghrelin, together with gastral and hippocampal ghrelin prepropeptide mRNA level, were significantly up-regulated in CUMS mice. Besides, the increased protein level of growth hormone secretagogue receptor (GHSR) in hippocampus were also detected. These results suggested that the endogenous ghrelin/GHSR pathway activated by CUMS plays a role in homeostasis. Further results showed that central treatment of ghrelin (10µg/rat/day for 2 weeks, i.c.v.) or GHRP-6 (the agonist of GHSR, 10µg/rat/day for 2 weeks, i.c.v.) significantly alleviated the depression-like behaviors induced by CUMS in FST and sucrose preference test (SPT). Based on these results, we concluded that central GHSR is involved in the antidepressant-like effect of exogenous ghrelin treatment, and ghrelin/GHSR may have the inherent neuromodulatory properties against depressive symptoms.

Curcumin ameliorates neuropathic pain by down-regulating spinal IL-1ß via suppressing astroglial NALP1 inflammasome and JAK2-STAT3 signalling.

Curcumin has been shown to possess strong anti-inflammatory activity in many diseases. It has been demonstrated that the janus kinase 2 (JAK2)-signal transducer and activator of transcription 3 (STAT3) cascade and the NAcht leucine-rich-repeat protein 1 (NALP1) inflammasome are important for the synthesis of Pro-Interleukin (IL)-1ß and the processing of the inactive protein to its mature form, which plays an active role in the pathogenesis of neuropathic pain. The present study showed that repeated intraperitoneal injection of curcumin ameliorated SNI-induced mechanical and cold allodynia in a dose-dependent manner and inhibited the elevation of spinal mature IL-1ß protein levels. Additionally, repeated curcumin treatment significantly inhibited the aggregation of the NALP1 inflammasome and the activation of the JAK2-STAT3 cascade in spinal astrocytes. Furthermore, the genetic down-regulation of NALP1 inflammasome activation by NALP1 siRNA and the pharmacological inhibition of the JAK2-STAT3 cascade by AG490 markedly inhibited IL-1ß maturation and Pro-IL-1ß synthesis, respectively, and reduced SNI-induced pain hypersensitivity. Our results suggest that curcumin attenuated neuropathic pain and down-regulated the production of spinal mature IL-1ß by inhibiting the aggregation of NALP1 inflammasome and the activation of the JAK2-STAT3 cascade in astrocytes.

Opposite Sex Contact and Isolation: A Novel Depression/Anxiety Model.

To mimic human mood disorders, traditional chronic stresses and social defeat stress have been developed and widely applied. However, these active stresses do not mimic the emotional flaws induced by stresses, and their input levels vary greatly. Also, emotional stresses resulting from social unobtainability remain largely elusive due to the lack of useful animal models. In this study, we developed a mouse model named "opposite sex contact and isolation" (OSCI) and found that OSCI induced significant social avoidance, anhedonia, and anxiety. These behavioral defects developed differently after 7 days of OSCI. The social avoidance behavior was self-curable while anxiety gradually worsened but was alleviated by re-pairing with the same female partner. Corresponding to the behavior changes, the plasma corticosterone and phosphorylated cAMP response element binding protein levels were decreased in the nucleus accumbens of the mice that experienced isolation. Together, this study has developed a novel strategy for depression/anxiety modeling and shows that OSCI may be a useful tool for studying the lovelorn/lovesick type of depression.

The Analgesic and Antineuroinflammatory Effect of Baicalein in Cancer-Induced Bone Pain.

Cancer-induced bone pain (CIBP) is a severe type of chronic pain. It is imperative to explore safe and effective analgesic drugs for CIBP treatment. Baicalein (BE), isolated from the traditional Chinese herbal medicine Scutellaria baicalensis Georgi (or Huang Qin), has been demonstrated to have anti-inflammatory and neuroprotective effects. In this study, we examined the effect of BE on CIBP and the mechanism of this effect. Intrathecal and oral administration of BE at different doses could alleviate the mechanical allodynia in CIBP rats. Intrathecal 100 µg BE could inhibit the production of IL-6 and TNF-α in the spinal cord of CIBP rats. Moreover, intrathecal 100 µg BE could effectively inhibit the activation of p-p38 and p-JNK MAPK signals in CIBP rats. The analgesic effect of BE may be associated with the inhibition of the expression of the inflammatory cytokines IL-6 and TNF-α and through the activation of p-p38 and p-JNK MAPK signals in the spinal cord. These findings suggest that BE is a promising novel analgesic agent for CIBP.

[Effect of Electroacupuncture Stimulation of "Baihui" (GV 20) , etc. on Changes of Behavior and Plasma Ghrelin Content in Depression Rats].

OBJECTIVE: To observe the effect of electroacupuncture (EA) stimulation of "Baihui" (GV 20) + "Anmian" (EX-HN 16) and "Baihui" (GV 20) + "Zusanli" (ST 36) on behavior reactions and plasma ghrelin level in depression rats, so as to explore the correlation between its antidepressant effect and plasma ghrelin level. METHODS: A total of 45 SD rats were randomly divided into 5 groups: normal control, model, Baihui (GV 20) + Anmian (EX-HN 16), Baihui (GV 20) + Zusanli (ST 36) and medication (clomipramine) groups, with 9 rats in each group. The depression model (unpredictable chronic mild stresses, UC-MS) was established by giving the animals with higher temperature environment (45 °C, 5 min), forced ice-water swimming (0- 4 °C, 5 min) , day and night reversal environment (12 h), stroboflash stimulation (12 h), noisy stimulation (12 h), rocking-bed movement (30 min) and damp pad dwelling (6-24 h), etc. for 4 weeks. EA was applied to GV 20-EX-HN 16, and GV 20-ST 36 for 30 min once every other day for 4 weeks after modeling. For rats of the medication group, clomipramine (5 mg/kg) was given (i. p. ) once a day for 4 weeks after modeling. The forced swimming test, sucrose preference test and open field test were used to evaluate the rats depressive-like behavior. Plasma ghrelin content was assayed by ELISA. RESULTS: After exposure to UCMS for 4 weeks, the immobility time was significantly increased, and the struggling time was significantly decreased in the model group (P < 0.05, P < 0.01). In comparison with the model group, the immobility time levels were obviously decreased, while the struggling time and sucrose preference were markedly increased in the Baihui (GV 20) + Anmian (EX-HN 16) , Baihui (GV 20) + Zusanli (ST 36) and medication groups (P < 0.05, P < 0.01). No significant changes were found in the rearing times and total distance of open-field test (locomotor activity) and plasma ghrelin content among the 5 groups among all the groups (P > 0.05). No significant differences were found among the two EA and medication groups in the decreased immobility time and the increased struggling times and sucrose preference levels (P > 0.05). CONCLUSION: EA intervention can improve the depression rats' hopeless behavior of forced swimming test and anhedonia behavior (sucrose preference test) , which may be not correlated to plasma ghrelin level at the late-stages and the antidepressant effect of EA intervention.

[Electroacupuncture Intervention Enhances Splenic Natural Killer Cell Activity via Inhibiting Phosphorylation of ERK 5 in the Hypothalamus of Surgically Traumatized Rats].

OBJECTIVE: To observe the effect of electroacupuncture (EA) on cytotoxic activity of splenic natural killer (NK) cells after surgical trauma via extracellular signal-regulated kinase (ERK) 5 pathway in the rats' hypothalamus, so as to explore its mechanism underlying improving immune disorders after surgery. METHODS: Sprague-Dawley rats were randomly divided into the following 6 groups: control, trauma model, EA, sham EA, 4 nmol-BIX 02188 (an inhibitor for ERK 5 catalytic activity) and 20 nmol-BIX 02188 (n = 6 rats per group). The surgical trauma model was established by making a longitudinal incision (6 cm in length) along the median line of the back to expose the spinal column and another longitudinal incision along the abdominal median line. EA (2 Hz/15 Hz, 1 - 2 mA) was applied to bilateral "Zusanli" (ST 36) for 30 min immediately after surgery. For rats of the BIX groups, intra-lateral ventricular microinjection of BIX 02188 (10 µL, 4 nmol or 20 nmol, or saline for control rats) was conducted 30 min before the surgery. The expression level and protein of phosphorylated ERK 5 (p-ERK 5) and corticotropin-releasing factor (CRF) protein were measured by immunohistochemistry and Western blot, respectively. The cytotoxicity of splenic NK cells and the expression of splenic Perforin and Granzyme-B genes were measured by lactate dehydrogenase (LDH) release assay and real-time PCR, respectively. RESULTS: In comparison with the control group, hypothalamic p-ERK 5 immunoactivity, p-ERK 5 protein and CRF protein expression levels were significantly up-regulated in the model group (P<0. 01, P<0. 05), while splenic NK cell cytotoxicity and Perforin mRNA and Granzyme-B mRNA expression levels were notably down-regulated in the model group (P <0. 05, P < 0. 01). Following EA and administration of ERK 5 antagonist, the increased expression levels of p-ERK 5 immunoactivity in the EA group, and p-ERK 5 and CRF proteins in both EA and 20 nmol-BIX 02188 groups were obviously down-regulated (P<0. 05, P<0. 01), without changes in the sham EA and 4 nmol-BIX 02188 groups (P>0. 05) except the increased p-ERK 5 protein in the 4 nmol-BIX 02188 group. In addition, the down-regulated NK cell activity, Perforin mRNA and Granzyme-B mRNA expression levels were significantly reversed in the EA and 20 nmol-BIX 02188 groups (P<0. 05, P<0. 01). No significant differences were found between the EA group and 20 nmol-BIX 02188 group in down-regulating hypothalamic p-ERK 5 and CRF protein expression and up-regulating splenic NK cytotoxicity and Perforin and Granzyme-B gene expression (P>0. 05). CONCLUSION: EA can promote the cytotoxicity of splenic NK cells in surgical trauma rats, which may be closely associated with its functions in down-regulating trauma-induced activation of ERK 5 pathway and production of CRF in the hypothalamus.

Early single Aspirin-triggered Lipoxin blocked morphine anti-nociception tolerance through inhibiting NALP1 inflammasome: Involvement of PI3k/Akt signaling pathway.

Clinical usage of opioids in pain relief is dampened by analgesic tolerance after chronic exposure, which is related to opioid-associated neuroinflammation. In the current study, which is based on a chronic morphine tolerance rat model and sustained morphine treatment on primary neuron culture, it was observed that Akt phosphorylation, cleaved-Caspase-1-dependent NALP1 inflammasome activation and IL-1ß maturation in spinal cord neurons were significantly enhanced by morphine. Moreover, treatment with LY294002, a specific inhibitor of PI3k/Akt signaling, significantly reduced Caspase-1 cleavage, NALP1 inflammasome activation and attenuated morphine tolerance. Tail-flick tests demonstrated that pharmacological inhibition on Caspase-1 activation or antagonizing IL-1ß dramatically blocked the development of morphine tolerance. The administration of an exogenous analogue of lipoxin, Aspirin-triggered Lipoxin (ATL), caused a decline in Caspase-1 cleavage, inflammasome activation and mature IL-1ß production and thus attenuated the development of morphine tolerance by inhibiting upstream Akt phosphorylation. Additionally, treatment with DAMGO, a selective µ-opioid receptor peptide, significantly induced Akt phosphorylation, Caspase-1 cleavage and anti-nociception tolerance, all of which were attenuated by ATL treatment. Taken together, the present study revealed the involvement of spinal NALP1 inflammasome activation in the development of morphine tolerance and the role of the µ-receptor/PI3k-Akt signaling/NALP1 inflammasome cascade in this process. By inhibiting this signaling cascade, ATL blocked the development of morphine tolerance.

Inhibition of p38 mitogen-activated protein kinase activation in the rostral anterior cingulate cortex attenuates pain-related negative emotion in rats.

The emotional components of pain are far less studied than the sensory components. Previous studies have indicated that the rostral anterior cingulate cortex (rACC) is implicated in the affective response to noxious stimuli. Activation of p38 mitogen-activated protein kinase (MAPK) in the spinal cord has been documented to play an important role in diverse kinds of pathological pain states. We used formalin-induced conditioned place aversion (F-CPA) in rats, an animal model believed to reflect the emotional response to pain, to investigate the involvement of p38 MAPK in the rACC after the induction of affective pain. Intraplantar formalin injection produced a significant activation of p38 MAPK, as well as mitogen-activated kinase kinase (MKK) 3 and MKK6, its upstream activators, in the bilateral rACC. p38 MAPK was elevated in both NeuN-positive neurons and Iba1-positive microglia in the rACC, but not GFAP-positive cells. Blocking p38 MAPK activation in the bilateral rACC using its specific inhibitor SB203580 or SB239063 dose-dependently suppressed the formation of F-CPA. Inhibiting p38 MAPK activation did not affect formalin-induced two-phase spontaneous nociceptive response and low intensity electric foot-shock induced CPA. The present study demonstrated that p38 MAPK signaling pathway in the rACC contributes to pain-related negative emotion. Thus, a new pharmacological strategy targeted at the p38 MAPK cascade may be useful in treating pain-related emotional disorders.

Effects of chronic electroacupuncture on depression- and anxiety-like behaviors in rats with chronic neuropathic pain.

Growing evidence indicates that chronic neuropathic pain is frequently accompanied by an array of psychiatric diseases, such as depression and anxiety. Electroacupuncture (EA), as one therapy of traditional Chinese medicine, has displayed potent antidepressant-like effects in numerous clinical studies. The present study was designed to examine the possible effects of EA on the depressive and anxiety disorders induced by neuropathic pain. A classic rat model of neuropathic pain was produced by chronic constriction injury (CCI) of the sciatic nerve. EA was performed on acupoints "Bai-Hui" (GV20) and unilateral "Yang-Ling-Quan" (GB34). The antidepressive and anxiolytic effects of EA treatment were analyzed using the forced swimming test (FST) and the elevated plus maze (EPM) test, respectively. CCI resulted in remarkable depression- and anxiety-like behaviors, whereas the chronic EA treatment significantly improved the behavioral deficits of CCI rats. Moreover, the phosphorylation level of the NMDA receptor type 1 (NR1) subunit was decreased in the hippocampus of CCI rats. Intriguingly, continuous EA treatment effectively blocked this decrease in the levels of pNR1. These results suggested that EA has antidepressive and anxiolytic effects on rats with neuropathic pain and that this might be associated with restoring the phosphorylation of NR1 in the hippocampus.