Anti-depressive mechanism of repetitive transcranial magnetic stimulation in rat: the role of the endocannabinoid system

rTMS Ameliorates time-varying depression and social behaviors in stimulated space complex environment associated with VEGF signaling

Studies have indicated that medium- to long-duration spaceflight may adversely affect astronauts' emotional and social functioning. Emotion modulation can significantly impact astronauts' well-being, performance, mission safety and success. However, with the increase in flight time, the potential alterations in emotional and social performance during spaceflight and their underlying mechanisms remain to be investigated, and targeted therapeutic and preventive interventions have yet to be identified. We evaluated the changes of emotional and social functions in mice with the extension of the time in simulated space complex environment (SSCE), and simultaneously monitored changes in brain tissue of vascular endothelial growth factor (VEGF), matrix metalloproteinase-9 (MMP-9), and inflammation-related factors. Furthermore, we assessed the regulatory role of repetitive transcranial magnetic stimulation (rTMS) in mood and socialization with the extension of the time in SSCE, as well as examining alterations of VEGF signaling in the medial prefrontal cortex (mPFC). Our findings revealed that mice exposed to SSCE for 7 days exhibited depressive-like behaviors, with these changes persisting throughout SSCE period. In addition, 14 days of rTMS treatment significantly ameliorated SSCE-induced emotional and social dysfunction, potentially through modulation of the level of VEGF signaling in mPFC. These results indicates that emotional and social disorders increase with the extension of SSCE time, and rTMS can improve the performance, which may be related to VEGF signaling. This study offers insights into potential pattern of change over time for mental health issues in astronauts. Further analysis revealed that rTMS modulates emotional and social dysfunction during SSCE exposure, with its mechanism potentially being associated with VEGF signaling.

Repetitive transcranial magnetic stimulation (rTMS) for depressive-like symptoms in rodent animal models

Repetitive transcranial magnetic stimulation (rTMS) emerged as a non-invasive brain stimulation technique in the treatment of psychiatric disorders. Both preclinical and clinical studies as well as systematic reviews provide a heterogeneous picture, particularly concerning the stimulation protocols used in rTMS. Here, we present a review of rTMS effects in rodent models of depressive-like symptoms with the aim to identify the most relevant factors that lead to an increased therapeutic success. The influence of different factors, such as the stimulation parameters (stimulus frequency and intensity, duration of stimulation, shape and positioning of the coil), symptom severity and individual characteristics (age, species and genetic background of the rodents), on the therapeutic success are discussed. Accumulating evidence indicates that rTMS ameliorates a multitude of depressive-like symptoms in rodent models, most effectively at high stimulation frequencies (≥5 Hz) especially in adult rodents with a pronounced pathological phenotype. The therapeutic success of rTMS might be increased in the future by considering these factors and using more standardized stimulation protocols.

A mitochondrial nexus in major depressive disorder: Integration with the psycho-immune-neuroendocrine network

Nervous system processes, including cognition and affective state, fundamentally rely on mitochondria. Impaired mitochondrial function is evident in major depressive disorder (MDD), reflecting cumulative detrimental influences of both extrinsic and intrinsic stressors, genetic predisposition, and mutation. Glucocorticoid 'stress' pathways converge on mitochondria; oxidative and nitrosative stresses in MDD are largely mitochondrial in origin; both initiate cascades promoting mitochondrial DNA (mtDNA) damage with disruptions to mitochondrial biogenesis and tryptophan catabolism. Mitochondrial dysfunction facilitates proinflammatory dysbiosis while directly triggering immuno-inflammatory activation via released mtDNA, mitochondrial lipids and mitochondria associated membranes (MAMs), further disrupting mitochondrial function and mitochondrial quality control, promoting the accumulation of abnormal mitochondria (confirmed in autopsy studies). Established and putative mechanisms highlight a mitochondrial nexus within the psycho-immune neuroendocrine (PINE) network implicated in MDD. Whether lowering neuronal resilience and thresholds for disease, or linking mechanistic nodes within the MDD pathogenic network, impaired mitochondrial function emerges as an important risk, a functional biomarker, providing a therapeutic target in MDD. Several treatment modalities have been demonstrated to reset mitochondrial function, which could benefit those with MDD.

Transcriptional changes in the rat brain induced by repetitive transcranial magnetic stimulation

Introduction

Transcranial Magnetic Stimulation (TMS) is a noninvasive technique that uses pulsed magnetic fields to affect the physiology of the brain and central nervous system. Repetitive TMS (rTMS) has been used to study and treat several neurological conditions, but its complex molecular basis is largely unexplored.

Methods

Utilizing three experimental rat models (in vitro, ex vivo, and in vivo) and employing genome-wide microarray analysis, our study reveals the extensive impact of rTMS treatment on gene expression patterns.

Results

These effects are observed across various stimulation protocols, in diverse tissues, and are influenced by time and age. Notably, rTMS-induced alterations in gene expression span a wide range of biological pathways, such as glutamatergic, GABAergic, and anti-inflammatory pathways, ion channels, myelination, mitochondrial energetics, multiple neuron-and synapse-specific genes.

Discussion

This comprehensive transcriptional analysis induced by rTMS stimulation serves as a foundational characterization for subsequent experimental investigations and the exploration of potential clinical applications.

Endocannabinoid signaling in adult hippocampal neurogenesis: A mechanistic and integrated perspective

Dentate gyrus of the hippocampus continuously gives rise to new neurons, namely, adult-born granule cells, which contribute to conferring plasticity to the mature brain throughout life. Within this neurogenic region, the fate and behavior of neural stem cells (NSCs) and their progeny result from a complex balance and integration of a variety of cell-autonomous and cell-to-cell-interaction signals and underlying pathways. Among these structurally and functionally diverse signals, there are endocannabinoids (eCBs), the main brain retrograde messengers. These pleiotropic bioactive lipids can directly and/or indirectly influence adult hippocampal neurogenesis (AHN) by modulating, both positively and negatively, multiple molecular and cellular processes in the hippocampal niche, depending on the cell type or stage of differentiation. Firstly, eCBs act directly as cell-intrinsic factors, cell-autonomously produced by NSCs following their stimulation. Secondly, in many, if not all, niche-associated cells, including some local neuronal and nonneuronal elements, the eCB system indirectly modulates the neurogenesis, linking neuronal and glial activity to regulating distinct stages of AHN. Herein, we discuss the crosstalk of the eCB system with other neurogenesis-relevant signal pathways and speculate how the hippocampus-dependent neurobehavioral effects elicited by (endo)cannabinergic medications are interpretable in light of the key regulatory role that eCBs play on AHN.

High-frequency repetitive transcranial magnetic stimulation regulates neural oscillations of the hippocampus and prefrontal cortex in mice by modulating endocannabinoid signalling

BACKGROUND

Neural oscillations play a role in the antidepressant effects of repetitive transcranial magnetic stimulation (rTMS). However, the effects of high-frequency rTMS on the neural oscillations of the medial prefrontal cortex (mPFC) and hippocampus (HPC) and its molecular mechanism have not been fully clarified.

METHODS

The depressive-like behaviours, local field potentials (LFPs) of the ventral HPC (vHPC)-mPFC, and alternations of endocannabinoid system (ECS) in the HPC and mPFC were observed after rTMS treatment. Meanwhile, depressive-like behaviours and LFPs were also observed after cannabinoid type-1 receptor (CB1R) antagonist AM281 or monoacylglycerol lipase inhibitor JZL184 injection. Moreover, the antidepressant effect of rTMS was further assessed in glutamatergic-CB1R and gamma-amino butyric acid (GABA)-ergic -CB1R knockout mice.

RESULTS

Alternations of endocannabinoids and energy value and synchronisation of mPFC-vHPC, especially the decrease of theta oscillation induced by CUMS, were alleviated by rTMS. JZL184 has similar effects to rTMS and AM281 blocked the effects of rTMS. GABAergic-CB1R deletion inhibited CUMS-induced depressive-like behaviours whereas Glutaminergic-CB1R deletion dampened the antidepressant effects of rTMS.

LIMITATIONS

The immediate effect of rTMS on field-potential regulation was not observed. Moreover, the role of region-specific regulation of the ECS in the antidepressant effect of rTMS was unclear and the effects of cell-specific CB1R knockout on neuronal oscillations of the mPFC and vHPC should be further investigated.

CONCLUSION

Endocannabinoid system mediated the antidepressant effects and was involved in the regulation of LFP in the vHPC-mPFC of high-frequency rTMS.

Thomas F, Battaglia F. High-frequency rTMS modulates emotional behaviors and structural plasticity in layers II/III and V of the mPFC

Repetitive transcranial magnetic stimulation (rTMS) is a noninvasive neuromodulation technique, and it has been increasingly used as a nonpharmacological intervention for the treatment of various neurological and neuropsychiatric diseases, including depression. In humans, rTMS over the prefrontal cortex is used to induce modulation of the neural circuitry that regulates emotions, cognition, and depressive symptoms. However, the underlying mechanisms are still unknown. In this study, we investigated the effects of a short (5-day) treatment with high-frequency (HF) rTMS (15 Hz) on emotional behavior and prefrontal cortex morphological plasticity in mice. Mice that had undergone HF-rTMS showed an anti-depressant-like activity as evidenced by decreased immobility time in both the Tail Suspension Test and the Forced Swim Test along with increased spine density in both layer II/III and layer V apical and basal dendrites. Furthermore, dendritic complexity assessed by Sholl analysis revealed increased arborization in the apical portions of both layers, but no modifications in the basal dendrites branching. Overall, these results indicate that the antidepressant-like activity of HF-rTMS is paralleled by structural remodeling in the medial prefrontal cortex.

Investigating repetitive transcranial magnetic stimulation on cannabis use and cognition in people with schizophrenia

Cannabis use disorder (CUD) occurs at high rates in schizophrenia, which negatively impacts its clinical prognosis. These patients have greater difficulty quitting cannabis which may reflect putative deficits in the dorsolateral prefrontal cortex (DLPFC), a potential target for treatment development. We examined the effects of active versus sham high-frequency (20-Hz) repetitive transcranial magnetic stimulation (rTMS) on cannabis use in outpatients with schizophrenia and CUD. Secondary outcomes included cannabis craving/withdrawal, psychiatric symptoms, cognition and tobacco use. Twenty-four outpatients with schizophrenia and CUD were enrolled in a preliminary double-blind, sham-controlled randomized trial. Nineteen participants were randomized to receive active (n = 9) or sham (n = 10) rTMS (20-Hz) applied bilaterally to the DLPFC 5x/week for 4 weeks. Cannabis use was monitored twice weekly. A cognitive battery was administered pre- and post-treatment. rTMS was safe and well-tolerated with high treatment retention (~90%). Contrast estimates suggested greater reduction in self-reported cannabis use (measured in grams/day) in the active versus sham group (Estimate = 0.33, p = 0.21; Cohen’s d = 0.72), suggesting a clinically relevant effect of rTMS. A trend toward greater reduction in craving (Estimate = 3.92, p = 0.06), and significant reductions in PANSS positive (Estimate = 2.42, p = 0.02) and total (Estimate = 5.03, p = 0.02) symptom scores were found in the active versus sham group. Active rTMS also improved attention (Estimate = 6.58, p < 0.05), and suppressed increased tobacco use that was associated with cannabis reductions (Treatment x Time: p = 0.01). Our preliminary findings suggest that rTMS to the DLPFC is safe and potentially efficacious for treating CUD in schizophrenia.

CB1 Ligand AM251 Induces Weight Loss and Fat Reduction in Addition to Increased Systemic Inflammation in Diet-Induced Obesity

Diet-induced obesity (DIO) reduces fatty acid oxidation in skeletal muscle and decreases circulating levels of adiponectin. Endocannabinoid signaling is overactive in obesity, with some effects abated by antagonism of cannabinoid receptor 1 (CB₁). This research aimed to determine if treatment with the global CB₁ antagonist/inverse agonist, AM251, in high-fat diet (HFD) fed rats influenced adiponectin signaling in skeletal muscle and a “browning” of white adipose tissue (WAT) defined by UCP1 expression levels. Male Sprague Dawley rats consumed an HFD (21% fat) for 9 weeks before receiving daily intraperitoneal injections with vehicle or AM251 (3 mg/kg) for 6 weeks. mRNA expression of genes involved in metabolic functions were measured in skeletal muscle and adipose tissue, and blood was harvested for the measurement of hormones and cytokines. Muscle citrate synthase activity was also measured. AM251 treatment decreased fat pad weight (epididymal, peri-renal, brown), and plasma levels of leptin, glucagon, ghrelin, and GLP-1, and increased PAI-1 along with a range of pro-inflammatory and anti-inflammatory cytokines; however, AM251 did not alter plasma adiponectin levels, skeletal muscle citrate synthase activity or mRNA expression of the genes measured in muscle. AM251 treatment had no effect on white fat UCP1 expression levels. AM251 decreased fat pad mass, altered plasma hormone levels, but did not induce browning of WAT defined by UCP1 mRNA levels or alter gene expression in muscle treated acutely with adiponectin, demonstrating the complexity of the endocannabinoid system and metabolism. The CB₁ ligand AM251 increased systemic inflammation suggesting limitations on its use in metabolic disorders.

Repetitive Transcranial Magnetic Stimulation Improves Depression-like Behavior in Rats by Promoting Neural Stem Cell Proliferation and Differentiation

Repetitive transcranial magnetic stimulation (rTMS) is a novel non-invasive neuromodulation technique with neuroprotective properties and is used to treat depression. However, the underlying mechanism of action remains unclear. In this study, we examined the possible mechanism mediating the antidepressant effect of rTMS using animal experiments. Specific pathogen-free rats were treated with rTMS after exposure to social isolation combined with chronic unpredictable mild stress (CUMS). After four weeks of CUMS, the rats exhibited a significant decrease in spatial working memory assessed using open-field testing, a general loss of interest assessed with the sucrose preference test, and a significant reduction in spatial recognition memory ability assessed using the Y-maze. These behavioral deficits were accompanied by decreased numbers of astrocytes in the hippocampus, decreased expression of glial fibrillary acidic protein (GFAP), increased numbers of neural stem cells (NSCs), and increased expression of nestin protein. These results indicated that neuron damage occurred in the depression-like rats. After rTMS intervention, the depression-like behavior was alleviated significantly, and the numbers of NSCs and astrocytes, as well as the expression of GFAP and nestin proteins, returned to normal levels. Overall, it is likely that attenuation of NSC proliferation and differentiation into astrocytes produced a neuroprotective effect on hippocampal neurons, which might partly explain the mechanism by which rTMS alleviates depression.

Neuromodulation and Hippocampal Neurogenesis in Depression: A Scoping Review

The 'neurogenesis hypothesis of depression' emphasizes the importance of upregulated hippocampal neurogenesis for the efficacy of antidepressant treatment. Neuromodulation is a promising therapeutic method that stimulates neural circuitries to treat neuropsychiatric illnesses. We conducted a scoping review on the neurogenic and antidepressant outcomes of neuromodulation in animal models of depression. PubMed, Web of Science, and PsycInfo were comprehensively searched for full-text English articles from inception to October 5, 2021. Data screening and extraction were conducted independently by two researchers. Seventeen eligible studies were included in this review. The majority of studies used non-invasive neuromodulation (n = 14) and assessed neurogenesis using neural proliferation (n = 16) and differentiation markers (n = 9). Limited reports (n = 2) used neurogenic inhibitors to evaluate the role of neurogenesis on the depressive-like behavioral outcomes. Overall, neuromodulation substantially effectuated both hippocampal cell proliferation and antidepressant-like behavior in animal models of depression, with some providing evidence for enhanced neuronal differentiation and maturation. The proposed neurogenic-related mechanisms mediating the neuromodulation efficacies included neurotrophic processes, anti-apoptotic pathways, and normalization of HPA axis functions. Further research is warranted to explore the role of neuromodulation-induced neurogenic effects on treatment efficacies and to elucidate the underlying molecular mechanisms.

Rapid treatments for depression: Endocannabinoid system as a therapeutic target

Current first-line treatments for major depressive disorder (MDD), i.e., antidepressant drugs and psychotherapy, show delayed onset of therapeutic effect as late as 2-3 weeks or more. In the clinic, the speed of beginning of the actions of antidepressant drugs or other interventions is vital for many reasons. Late-onset means that depression, its related disability, and the potential danger of suicide remain a threat for some patients. There are some rapid-acting antidepressant interventions, such as sleep deprivation, ketamine, acute exercise, which induce a significant response, ranging from a few hours to maximally one week, and most of them share a common characteristic that is the activation of the endocannabinoid (eCB) system. Activation of this system, i.e., augmentation of eCB signaling, appears to have anti-depressant-like actions. This article puts the idea forward that the activation of eCB signaling represents a critical mechanism of rapid-acting therapeutic interventions in MDD, and this system might contribute to the development of novel rapid-acting treatments for MDD.

The antidepressant and anxiolytic effects of cannabinoids in chronic unpredictable stress: a preclinical systematic review and meta-analysis

Neuroscience research presents contradictory evidence in support of both the protective and destructive effects of cannabinoids in depression. Therefore, this systematic review and meta-analysis summarizes the existing preclinical literature on the effects of cannabinoid administration in the chronic unpredictable stress model of depression in order to evaluate the effects of cannabinoids and identify gaps in the literature. After protocol registration (PROSPERO #CRD42020219986), we systematically searched Scopus, Embase, Psychology & Behavioral Sciences Collection, APA PsychINFO, PubMed, CINAHL Complete, and ProQuest Dissertations & Theses Global from the earliest record of the databases, February 1964, to November 2020 for articles that met inclusion criteria (e.g., rodent subjects and administration of a cannabinoid. A total of 26 articles were included representing a sample size estimate of 1132 rodents with the majority of articles administering daily intraperitoneal injections during chronic unpredictable stress. These articles were evaluated using a modified SYRCLE's risk-of-bias tool. For each continuous behavioral measure, the standardized mean difference was calculated between cannabinoid and vehicle groups in rodents subjected to chronic unpredictable stress. The effects of cannabinoids on depressive-like behavior was evaluated using a multilevel mixed-effects model with effect size weights nested within control groups. Cannabinoid administration moderately improved the pooled negative effects of chronic unpredictable stress on anhedonia, learned helplessness, novelty suppressed feeding, time in the anxiogenic context, and entries into the anxiogenic context. Although the interpretations are limited, these findings suggest that with further investigation, cannabinoids may be a viable long-term treatment for stress-related psychopathologies such as depression.

Modulation of Endocannabinoid System Components in Depression: Pre-Clinical and Clinical Evidence

Depression is characterized by continuous low mood and loss of interest or pleasure in enjoyable activities. First-line medications for mood disorders mostly target the monoaminergic system; however, many patients do not find relief with these medications, and those who do suffer from negative side effects and a discouragingly low rate of remission. Studies suggest that the endocannabinoid system (ECS) may be involved in the etiology of depression and that targeting the ECS has the potential to alleviate depression. ECS components (such as receptors, endocannabinoid ligands, and degrading enzymes) are key neuromodulators in motivation and cognition as well as in the regulation of stress and emotions. Studies in depressed patients and in animal models for depression have reported deficits in ECS components, which is motivating researchers to identify potential diagnostic and therapeutic biomarkers within the ECS. By understanding the effects of cannabinoids on ECS components in depression, we enhance our understanding of which brain targets they hit, what biological processes they alter, and eventually how to use this information to design better therapeutic options. In this article, we discuss the literature on the effects of cannabinoids on ECS components of specific depression-like behaviors and phenotypes in rodents and then describe the findings in depressed patients. A better understanding of the effects of cannabinoids on ECS components in depression may direct future research efforts to enhance diagnosis and treatment.

Transcranial magnetic stimulation in animal models of neurodegeneration

Brain stimulation techniques offer powerful means of modulating the physiology of specific neural structures. In recent years, non-invasive brain stimulation techniques, such as transcranial magnetic stimulation (TMS) and transcranial direct current stimulation, have emerged as therapeutic tools for neurology and neuroscience. However, the possible repercussions of these techniques remain unclear, and there are few reports on the incisive recovery mechanisms through brain stimulation. Although several studies have recommended the use of non-invasive brain stimulation in clinical neuroscience, with a special emphasis on TMS, the suggested mechanisms of action have not been confirmed directly at the neural level. Insights into the neural mechanisms of non-invasive brain stimulation would unveil the strategies necessary to enhance the safety and efficacy of this progressive approach. Therefore, animal studies investigating the mechanisms of TMS-induced recovery at the neural level are crucial for the elaboration of non-invasive brain stimulation. Translational research done using animal models has several advantages and is able to investigate knowledge gaps by directly targeting neuronal levels. In this review, we have discussed the role of TMS in different animal models, the impact of animal studies on various disease states, and the findings regarding brain function of animal models after TMS in pharmacology research.

Commonalities for comorbidity: Overlapping features of the endocannabinoid system in depression and epilepsy

A wealth of clinical and pre-clinical data supports a bidirectional comorbidity between depression and epilepsy. This suggests commonalities in underlying mechanisms that may serve as targets for more effective treatment strategies. Unfortunately, many patients with this comorbidity are highly refractory to current treatment strategies, while others experience a worsening of one arm of the comorbidity when treating the other arm. This highlights the need for novel pharmaceutical targets that may provide safe and effective relief for both depression and epilepsy symptoms. The endocannabinoid system (ECS) of the brain has become an area of intense interest for possible roles in depression and epilepsy. Several existing literature reviews have provided in-depth analysis of the involvement of various aspects of the ECS in depression or epilepsy separately, while others have addressed the effectiveness of different treatment strategies targeting the ECS in either condition individually. However, there is not currently a review that considers the ECS when both conditions are comorbid. This mini-review will address areas of common overlap between the ECS in depression and in epilepsy, such as commonalities in endocannabinoids themselves, their receptors, and degradative enzymes. These areas of overlap will be discussed alongside their implications for treatment of this challenging comorbidity.

Antidepressant-like effect of rosmarinic acid during LPS-induced neuroinflammatory model: The potential role of cannabinoid receptors/PPAR-γ signaling pathway

Rosmarinic acid (RA), an ester of caffeic acid and 3, 4-dihydroxyphenyllactic acid, has anti-inflammatory and neuroprotective activities. Herein, this study investigated in silico the drug-likeness and the potential molecular targets to RA. Moreover, it tested the antidepressant-like potential of RA in the lipopolysaccharide (LPS)-induced depression model. RA (MW = 360.31 g/mol) meets the criteria of both Lipinski's rule of five and the Ghose filter. It also attends to relevant pharmacokinetic parameters. Target prediction analysis identified RA's potential targets and biological activities, including the peroxisome proliferator-activated receptor (PPAR) and the cannabinoid receptors CB1 and CB2 . In vivo, RA's acute, repetitive, and therapeutic administration showed antidepressant-like effect since it significantly reduced the immobility time in the tail suspension test and increased grooming time in the splash test. Further, the pretreatment with antagonists of CB1 , CB2 , and PPAR-γ receptors significantly blocked the antidepressant-like effect of RA. Altogether, our findings suggest that cannabinoid receptors/PPAR-γ signaling pathways are involved with the antidepressant-like effect of RA. Moreover, this molecule meets important physicochemical and pharmacokinetic parameters that favor its bioavailability. RA constitutes a promising, innovative, and safe molecule for the pharmacotherapy of major depressive disorder.

Neuroprotective Effects and Therapeutic Potential of Transcorneal Electrical Stimulation for Depression

Transcorneal electrical stimulation (TES) has emerged as a non-invasive neuromodulation approach that exerts neuroprotection via diverse mechanisms, including neurotrophic, neuroplastic, anti-inflammatory, anti-apoptotic, anti-glutamatergic, and vasodilation mechanisms. Although current studies of TES have mainly focused on its applications in ophthalmology, several lines of evidence point towards its putative use in treating depression. Apart from stimulating visual-related structures and promoting visual restoration, TES has also been shown to activate brain regions that are involved in mood alterations and can induce antidepressant-like behaviour in animals. The beneficial effects of TES in depression were further supported by its shared mechanisms with FDA-approved antidepressant treatments, including its neuroprotective properties against apoptosis and inflammation, and its ability to enhance the neurotrophic expression. This article critically reviews the current findings on the neuroprotective effects of TES and provides evidence to support our hypothesis that TES possesses antidepressant effects.

Inhibition of CB1 receptor alleviates electroconvulsive shock-induced memory impairment by regulating hippocampal synaptic plasticity in depressive rats

Electroconvulsive therapy (ECT) is one of the most effective treatments for depression, but it can cause cognitive deficit. Unfortunately, effective preventive measures are still lacking. The endocannabinoid system is thought to play a key role in regulation of cognitive process. Whether the endocannabinoid system is involved in the learning and memory impairment caused by ECS remain unclear. In this work, we first found that cannabinoid receptor type 1 (CB1R) and 2-arachidonoylglycerol (2-AG) were strongly expressed in hippocampus by electroconvulsive shock (ECS) in a rat depression model established by chronic mild stress (CMS). Pharmacological inhibition of CB1R using AM251 in vivo resulted in a pronounced relief in ECS-induced spatial learning and memory impairment as well as in a marked reversal of impaired hippocampal long-term potentiation (LTP), and reduced synapse-related proteins expression. Furthermore, results of sucrose preference test (SPT) and open-field test (OFT) showed that AM251 had no significant impact on the therapeutic effects of ECS on pleasure and psychomotor activity. Taken together, we identified that CB1R is involved in the ECS-induced spatial learning and memory impairment and Inhibition of CB1R facilitates the recovery of memory impairment and hippocampal synaptic plasticity, without interfering with the therapeutic effects of ECS in depressed rats.

Peripheral endocannabinoid serum level in association with repetitive transcranial magnetic stimulation (rTMS) treatment in patients with major depressive disorder

Repetitive transcranial magnetic stimulation (rTMS) is an effective and well tolerable biological intervention in major depressive disorder (MDD) contributing to rapid symptom improvement. Molecular mechanisms underpinning the therapeutic effects of rTMS have still not been clarified. Recently published animal data implicated relevant associations with changes in endocannabinoid (eCB) brain levels during rTMS treatment, human studies, however, have not been published. In our study we assessed the detailed phenotypic spectrum of MDD and serum 2-arachidnoylglycerol (2-AG) and anandamide (AEA) levels in 18 patients with treatment-resistant depression before, immediately following, and two weeks after completion of a 10-day rTMS treatment. We found significant associations between serum 2-AG level changes from pretreatment to 2 weeks after treatment and symptom reduction. The greater the increase of 2-AG levels, the greater the improvement of depressive (p = 0.031), anxious (p = 0.007) and anhedonia symptoms (p = 0.047). Here we report for the first time a significant association of human circulating eCB and antidepressant effect of rTMS. Our data may indicate that direct stimulation of targeted brain areas can rapidly alleviate depressive complaints via activation of the eCB system.

Chronic unpredictable stress negatively regulates hippocampal neurogenesis and promote anxious depression-like behavior via upregulating apoptosis and inflammatory signals in adult rats

Psychological and physical stress play a pivotal role in etiology of anxiety and depression. Chronic psychological and physical stress modify various physiological phenomena, as a consequence of which oxidative stress, decreased neurotransmitter level, elevated corticosterone level and altered NSC homeostasis is observed. However, the precise mechanism by which chronic stress induce anxious depression and modify internal milieu is still unknown. Herein, we show that exposure to CUS increase oxidative stress, microgliosis, astrogliosis while it reduces hippocampal NSC proliferation, neuronal differentiation and maturation in adult rats. CUS exposure in rats reduce dopamine and serotonin level in cortex and hippocampus, which result in increased anxiety and depression-like phenotypes. We also found elevated level of NF-κB and TNF-α while decreased anti-inflammatory cytokine IL-10 level, that led to increased expression of Bax and cleaved Caspase-3 whereas down regulation of antiapoptotic protein Bcl2. Additionally, CUS altered adult hippocampal neurogenesis, increased gliosis and neuronal apoptosis in cerebral cortex and hippocampus which might be associated with reduced AKT and increased ERK signaling, as seen in the rat brain tissue. Taken together, these results indicate that CUS induce oxidative stress and neuroinflammation which directly affects NSC dynamics, monoamines levels and behavioral functions in adult rats.

A systematic, integrative review of the effects of the endocannabinoid system on inflammation and neurogenesis in animal models of affective disorders

The endocannabinoid (eCB) system is considered relevant in the pathophysiology of affective disorders, and a potential therapeutic target, as its hypoactivity is considered an important risk factor of depression. However, the biological mechanisms whereby the eCB system affects mood remain elusive. Through a systematic review, thirty-seven articles were obtained from the PubMed/Medline, Web of Science, Embase, PsychInfo, and CINAHL databases, investigating the role of the eCB system on the immune system and neurogenesis, as well as resulting behavioural effects in rodent models of affective disorders. Overall, activation of the eCB system appears to decrease depressive-like behaviour and to be anti-inflammatory, while promoting neuro- and synaptogenesis in various models. Activation of cannabinoid receptors (CBRs) is shown to be crucial in improving depressive-like and anxiety-like behaviour, although cannabidiol administration suggests a role of additional mechanisms. CB₁R signalling, as well as fatty acid amide hydrolase (FAAH) inhibition, are associated with decreased pro-inflammatory cytokines. Moreover, activation of CBRs is required for neurogenesis, which is also upregulated by FAAH inhibitors. This review is the first to assess the association between the eCB system, immune system and neurogenesis, alongside behavioural outcomes, across rodent models of affective disorders. We confirm the therapeutic potential of eCB system activation in depression and anxiety, highlighting immunoregulation as an important mechanism whereby dysfunctional behaviour and neurogenesis can be improved.

Effects of Sesame Oil Aroma on Mice after Exposure to Water Immersion Stress: Analysis of Behavior and Gene Expression in the Brain

(1) Background: Sesame has been popular as a healthy food since ancient times, and effects of the aroma component of roasted sesame are also expected. However, little research has been reported on its scent; (2) Methods: Jcl:ICR male mice were housed under water immersion stress for 24 h. Then, the scent of saline or sesame oil was inhaled to stress groups for 90 min. We investigated the effects of sesame oil aroma on the behavior and brains of mice; (3) Results: In an elevated plus maze test, the rate of entering to open arm and the staying time were decreased by the stress. These decrements were significantly enhanced by sesame oil aroma. Stress had a tendency to increase the serum corticosterone concentration, which was slightly decreased by the aroma. Expression of Kruppel-like factor-4 (Klf-4) and Dual-specificity phosphatase-1 (Dusp-1) in the striatum were increased by water immersion stress, and the level of Klf-4 and Dusp-1 in the striatum and hippocampus were significantly attenuated by sesame oil aroma (4) Conclusions: The present results strongly suggest that the odor component of sesame oil may have stress suppressing effects. Moreover, Klf-4 and Dusp-1 may be sensitive stress-responsive biomarkers.

Recovering from depression with repetitive transcranial magnetic stimulation (rTMS): a systematic review and meta-analysis of preclinical studies

Repetitive transcranial magnetic stimulation (rTMS) has gained growing interest for the treatment of major depression (MDD) and treatment-resistant depression (TRD). Most knowledge on rTMS comes from human studies as preclinical application has been problematic. However, recent optimization of rTMS in animal models has laid the foundations for improved translational studies. Preclinical studies have the potential to help identify optimal stimulation protocols and shed light on new neurobiological-based rationales for rTMS use. To assess existing evidence regarding rTMS effects on depressive-like symptoms in rodent models, we conducted a comprehensive literature search in accordance with PRISMA guidelines (PROSPERO registration number: CRD42019157549). In addition, we conducted a meta-analysis to determine rTMS efficacy, performing subgroup analyses to examine the impact of different experimental models and neuromodulation parameters. Assessment of the depressive-like phenotype was quite homogeneous whilst rTMS parameters among the 23 included studies varied considerably. Most studies used a stress-induced model. Overall, results show a largely beneficial effect of active rTMS compared to sham stimulation, as reflected in the statistically significant recovery of both helplessness (SDM 1.34 [1.02;1.66]) and anhedonic (SDM 1.87 [1.02;2.72]) profiles. Improvement of the depressive-like phenotype was obtained in all included models and independently of rTMS frequency. Nonetheless, these results have limited predictive value for TRD patients as only antidepressant-sensitive models were used. Extending rTMS studies to other MDD models, corresponding to distinct endophenotypes, and to TRD models is therefore crucial to test rTMS efficacy and to develop cost-effective protocols, with the potential of yielding faster clinical responses in MDD and TRD.

Mechanisms of repetitive transcranial magnetic stimulation for anti-depression: Evidence from preclinical studies

This review summarizes the anti-depressant mechanisms of repetitive transcranial magnetic stimulation in preclinical studies, including anti-inflammatory effects mediated by activation of nuclear factor-E2-related factor 2 signaling pathway, anti-oxidative stress effects, enhancement of synaptic plasticity and neurogenesis via activation of the endocannabinoid system and brain derived neurotrophic factor signaling pathway, increasing the content of monoamine neurotransmitters via inhibition of Sirtuin 1/monoamine oxidase A signaling pathway, and reducing the activity of the hypothalamic-pituitary-adrenocortical axis. We also discuss the shortcomings of transcranial magnetic stimulation in preclinical studies such as inaccurate positioning, shallow depth of stimulation, and difficulty in elucidating the neural circuit mechanism up- and down-stream of the stimulation target brain region.

Antidepressant-like effects of URB597 and JZL184 in male and female rats exposed to early life stress

Early life stress (ELS) may increase predisposition to depression. Despite extensive research, there is still a lack of knowledge of how to optimally treat depression. We aimed to establish a role for the endocannabinoid (ECB) system within the hippocampal-nucleus accumbens (NAc) network as a possible effective target in combating the pathophysiological development of depression-like behavior and neuronal alterations that are precipitated by ELS. Male and female rats were exposed to ELS during post-natal days (P) 7-14, injected with the fatty acid amide hydrolase (FAAH) inhibitor URB597 or the monoacylglycerol lipase (MAGL) inhibitor JZL184 for 2 weeks during late-adolescence (P45-60). Rats were tested starting at P90 for depressive- and anxiety-like behaviors as well as social preference and recognition; alterations in FAAH and MAGL activity; the expression of brain-derived neurotrophic factor (BDNF); and plasticity in the hippocampal-NAc pathway. FAAH and MAGL inhibitors during late-adolescence prevented: (i) the long-term effects of ELS on depression- and anxiety-like behavior and the impairment in social behavior and neuronal plasticity in males and females; (ii) ELS-induced alterations in MAGL activity in males' hippocampus and females' hippocampus and NAc; and (iii) ELS-induced alterations in BDNF in males' hippocampus and NAc and females' hippocampus. Significant correlations were observed between alterations in MAGL and BDNF levels and the behavioral phenotype. The findings suggest that alterations in MAGL activity and BDNF expression in the hippocampal-NAc network contribute to the depressive-like behavioral phenotype in ELS males and females. Moreover, the study suggests FAAH and MAGL inhibitors as potential intervention drugs for depression.

Repetitive transcranial magnetic stimulation activates glial cells and inhibits neurogenesis after pneumococcal meningitis

Pneumococcal meningitis (PM) causes damage to the hippocampus, a brain structure critically involved in learning and memory. Hippocampal injury-which compromises neurofunctional outcome-occurs as apoptosis of progenitor cells and immature neurons of the hippocampal dentate granule cell layer thereby impairing the regenerative capacity of the hippocampal stem cell niche. Repetitive transcranial magnetic stimulation (rTMS) harbours the potential to modulate the proliferative activity of this neuronal stem cell niche. In this study, specific rTMS protocols-namely continuous and intermittent theta burst stimulation (cTBS and iTBS)-were applied on infant rats microbiologically cured from PM by five days of antibiotic treatment. Following two days of exposure to TBS, differential gene expression was analysed by whole transcriptome analysis using RNAseq. cTBS provoked a prominent effect in inducing differential gene expression in the cortex and the hippocampus, whereas iTBS only affect gene expression in the cortex. TBS induced polarisation of microglia and astrocytes towards an inflammatory phenotype, while reducing neurogenesis, neuroplasticity and regeneration. cTBS was further found to induce the release of pro-inflammatory cytokines in vitro. We conclude that cTBS intensified neuroinflammation after PM, which translated into increased release of pro-inflammatory mediators thereby inhibiting neuroregeneration.

Enhancement of Neural Stem Cell Proliferation in Rats with Spinal Cord Injury by a Combination of Repetitive Transcranial Magnetic Stimulation (rTMS) and Human Umbilical Cord Blood Mesenchymal Stem Cells (hUCB-MSCs)

BACKGROUND This study was designed to explore the combined effects of repetitive transcranial magnetic stimulation (rTMS) and human umbilical cord blood mesenchymal stem cells (hUCB-MSCs) transplantation on neural stem cell proliferation in rats with spinal cord injury (SCI). MATERIAL AND METHODS SCI was induced in 90 rats by laminectomy at T10. Fifteen rats each were treated with 0.5 Hz rTMS or 10 Hz rTMS or underwent hUCB-MSC transplantation; 15 each were treated with 0.5 Hz rTMS+hUCB-MSCs or 10 Hz rTMS+hUCB-MSCs; and 15 were untreated (control group). The Basso, Beattie, and Bresnahan (BBB) scores and motor evoked potentials (MEPs) were measured, and all rats underwent biotin dextran-amine (BDA) tracing of the corticospinal tract (CST). The levels of expression of neural stem cell proliferation related proteins, including BrdU, nestin, Tuj1, Ng2+ and GFAP, were measured, and the levels of bFGF and EGF determined by Western blotting. RESULTS BBB scores and MEPs were increased after rTMS and hUCB-MSC transplantation, while histologically determined SCI-induced neuron apoptosis was attenuated. The numbers of BDA-positive fibers and Brdu-, nestin- and Tuj1-positive cells were markedly increased and the numbers of Ng2+- and GFAP-positive cells were markedly decreased following treatment with rTMS alone or rTMS plus hUCB-MSC transplantation. The levels of expression of bFGF and EGF were significantly upregulated following rTMS treatment and hUCB-MSC transplantation. Higher performance was observed after combined treatment with rTMS and hUCB-MSC transplantation than after either alone. CONCLUSIONS The combination of rTMS treatment and hUCB-MSC transplantation could attenuate SCI-induced neural stem cell apoptosis and motor dysfunction in rats.

Neuroprotective efficacy of different levels of high-frequency repetitive transcranial magnetic stimulation in mice with CUMS-induced depression: Involvement of the p11/BDNF/Homer1a signaling pathway

High-frequency repetitive transcranial magnetic stimulation (HF-rTMS) is widely used to treat depression. However, the underlying mechanism has not been identified, and there is uncertainty regarding the optimal choice of stimulus parameters, especially stimulus frequency. Our previous study in mice demonstrated that 10-Hz HF-rTMS ameliorated depression by inducing expression of Homer1a and reducing excitability of cortical pyramidal cells. The aims of this study were to compare the effects of 15-Hz and 25-Hz HF-rTMS in a model of chronic unpredictable mild stress (CUMS)-induced depression and investigate its possible molecular mechanism. Male C57BL/6J mice were treated with CUMS for 28 days followed by 15-Hz and 25-Hz rTMS for 4 weeks. The sucrose preference, open field, forced swimming, and tail suspension tests were used to evaluate depression-like behaviors. Immunostaining was performed to measure neuronal loss and neurogenesis. Apoptosis was detected by terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling staining. Expression of synapse-related proteins and the effects of HF-rTMS on the signaling pathway were examined using Western blot. The results showed that both 15-Hz and 25-Hz rTMS had significant antidepressant effects; 15-Hz rTMS seemed to be more effective than 25-Hz rTMS in preventing neuronal loss and promoting neurogenesis, while 25-Hz rTMS was superior to 15-Hz rTMS in facilitating synaptic plasticity. We also found that 15-Hz and 25-Hz rTMS markedly increased expression of p11, BDNF, Homer1a, and p-trkB proteins. These findings suggest that 15-Hz and 25-Hz HF-rTMS could exert neuroprotective effects to different degrees via multiple perspectives, which at least in part involve the p11/BDNF/Homer1a pathway.

Repetitive Transcranial Magnetic Stimulation Elicits Antidepressant- and Anxiolytic-like Effect via Nuclear Factor-E2-related Factor 2-mediated Anti-inflammation Mechanism in Rats

Repetitive transcranial magnetic stimulation (rTMS) treatment is widely accepted as an evidence-based treatment option for depression and anxiety. However, the underlying mechanism of this treatment maneuver has not been clearly understood. The chronic unpredictable mild stress (CUMS) procedure was used to establish depression and anxiety-like behavior in rats. The rTMS was performed with a commercially available stimulator for seven consecutive days, and then depression and anxiety-like behaviors were subsequently measured. The expression of nuclear factor-E2-related factor 2 (Nrf2) was measured by western-blot, and the level of tumor necrosis factor-α (TNF-α), inducible nitric oxide synthase (iNOS), interleukin-1β (IL-1β), and interleukin-6 (IL-6) was measured with Enzyme-linked immunesorbent assay (ELISA) analyzing kits. Furthermore, a small interfering RNA was employed to knockdown Nrf2, after which the neurobehavioral assessment, Nrf2 nuclear expression, and the amount of inflammation factors were evaluated. Application of rTMS exhibited a significant antidepressant and anxiolytic-like effect, which was associated with the increased Nrf2 nuclear translocation and reduced level of TNF-α, iNOS, IL-1β, and IL-6 in the hippocampus. Following Nrf2 silencing, the antidepressant and anxiolytic-like effect produced by rTMS was abolished. Moreover, the elevated Nrf2 nuclear translocation, and the reduced production of TNF-α, iNOS, IL-1β, and IL-6 in hippocampus mediated by rTMS, were reversed by Nrf2 knockdown. Together, these results reveal that the Nrf2-induced anti-inflammation effect is crucial in regulating antidepressant-related behaviors produced by rTMS.

Endocannabinoid System Components as Potential Biomarkers in Psychiatry

The high heterogeneity of psychiatric disorders leads to a lack of diagnostic precision. Therefore, the search of biomarkers is a fundamental aspect in psychiatry to reach a more personalized medicine. The endocannabinoid system (ECS) has gained increasing interest due to its involvement in many different functional processes in the brain, including the regulation of emotions, motivation, and cognition. This article reviews the role of the main components of the ECS as biomarkers in certain psychiatric disorders. Studies carried out in rodents evaluating the effects of pharmacological and genetic manipulation of cannabinoid receptors or endocannabinoids (eCBs) degrading enzymes were included. Likewise, the ECS-related alterations occurring at the molecular level in animal models reproducing some behavioral and/or neuropathological aspects of psychiatric disorders were reviewed. Furthermore, clinical studies evaluating gene or protein alterations in post-mortem brain tissue or in vivo blood, plasma, and cerebrospinal fluid (CSF) samples were analyzed. Also, the results from neuroimaging studies using positron emission tomography (PET) or functional magnetic resonance (fMRI) were included. This review shows the close involvement of cannabinoid receptor 1 (CB1r) in stress regulation and the development of mood disorders [anxiety, depression, bipolar disorder (BD)], in post-traumatic stress disorder (PTSD), as well as in the etiopathogenesis of schizophrenia, attention deficit hyperactivity disorder (ADHD), or eating disorders (i.e. anorexia and bulimia nervosa). On the other hand, recent results reveal the potential therapeutic action of the endocannabinoid tone manipulation by inhibition of eCBs degrading enzymes, as well as by the modulation of cannabinoid receptor 2 (CB2r) activity on anxiolytic, antidepressive, or antipsychotic associated effects. Further clinical research studies are needed; however, current evidence suggests that the components of the ECS may become promising biomarkers in psychiatry to improve, at least in part, the diagnosis and pharmacological treatment of psychiatric disorders.

Repetitive high-frequency transcranial magnetic stimulation reverses depressive-like behaviors and protein expression at hippocampal synapses in chronic unpredictable stress-treated rats by enhancing endocannabinoid signaling

The anti-depressant effect of repetitive transcranial magnetic stimulation (rTMS), a clinically-useful treatment for depression, is associated with changes to the endocannabinoid system (ECS). However, it is currently unknown whether different frequencies of rTMS alter the ECS differently. To test this, rats exposed to chronic unpredictable stress (CUS) were treated with rTMS at two different frequencies (5 (high) or 1 Hz (low), 1.26 Tesla) for 7 consecutive days. Twenty-four hours after the final rTMS treatment, we evaluated depressive-like behaviors and the expression of several synaptic proteins and ECS-related proteins in the hippocampus. In addition, we knocked-down diacylglycerol lipase alpha (DAGLα) and cannabinoid type 1 receptor (CB1R), two important components of the ECS, and measured depressive-like behaviors and synaptic protein expression following rTMS. Furthermore, we measured the expression levels of several components of the ECS system in hippocampal-derived astrocytes and neurons exposed to repetitive magnetic stimulation (rMS) with different parameters (5 or 1 Hz, 0.84 or 1.26 Tesla). Interestingly, we found that only high-frequency rTMS ameliorated depressive-like behaviors and normalized the expression of hippocampal synaptic proteins in CUS-treated rats; this effect was eliminated by knockdown of DAGLα or CB1R. Moreover, we found that rMS at 5 Hz increased the expression of DAGLα and CB1R in hippocampal astrocytes and neurons. Collectively, our results suggest that high-frequency rTMS exerts its anti-depressant effect by up-regulating DAGLα and CB1R.

Trans-cinnamaldehyde shows anti-depression effect in the forced swimming test and possible involvement of the endocannabinoid system

Depression is a mental disease that significantly reduces the quality of patients' life. Around 322 million people of all ages carry the heavy burden of depression on a worldwide scale, with a life-time prevalence of 20% according to the WHO. Trans-cinnamaldehyde (TCA) is an excellent COX-2 inhibitor in central nervous system which is a main constituent of GUIZHI as a member of traditional Chinese herb. Furthermore, previous studies demonstrated that TCA suppressed depression-like behavior in chronic unexpected mild stress, plus maze test and open field test. However, the molecular mechanism of TCA anti-depression effect is not clear. We examined the immobility of TCA pretreated male BALB/c mice in the forced swimming test (FST). Results show that TCA (50 mg/kg, po) revealed a significant effect on reduced immobility in the FST, compared with SAL group which indicated that TCA suppressed depression-like behavior. Moreover, TCA elevated the level of 5-HT and decreased the ratio of Glu/GABA in mice hippocampus. Compared with SAL + FST group, TCA + FST group significantly decreased COX-2, TRPV1 and CB1 protein level in mice hippocampus (p < 0.05, p < 0.05, p < 0.01). These findings suggest that TCA treatment exerted anti-depressive effect and was able to regulate neurotransmitters in the FST. This effect may have positive influence on the endocannabinoid (eCB) system.

Early life stress alters the developmental trajectory of corticolimbic endocannabinoid signaling in male rats

Early-life stress modulates the development of cortico-limbic circuits and increases vulnerability to adult psychopathology. Given the important stress-buffering role of endocannabinoid (eCB) signaling, we performed a comprehensive investigation of the developmental trajectory of the eCB system and the impact of exposure to early life stress induced by repeated maternal separation (MS; 3 h/day) from postnatal day 2 (PND2) to PND12. Tissue levels of the eCB molecules anandamide (AEA) and 2-arachidonoylglycerol (2-AG) were measured after MS exposures, as well under basal conditions at juvenile (PND14), adolescent (PND40) and adult (PND70) timepoints in the prefrontal cortex (PFC), amygdala and hippocampus. We also examined the effects of MS on CB₁ receptor binding in these three brain regions at PND40 and PND70. AEA content was found to increase from PND2 into adulthood in a linear manner across all brain regions, while 2-AG was found to exhibit a transient spike during the juvenile period (PND12-14) within the amygdala and PFC, but increased in a linear manner across development in the hippocampus. Exposure to MS resulted in bidirectional changes in AEA and 2-AG tissue levels within the amygdala and hippocampus and produced a sustained reduction in eCB function in the hippocampus at adulthood. CB₁ receptor densities across all brain regions were generally found to be downregulated later in life following exposure to MS. Collectively, these data demonstrate that early life stress can alter the normative ontogeny of the eCB system, resulting in a sustained deficit in eCB function, particularly within the hippocampus, in adulthood.

Effects of rTMS on Hippocampal Endocannabinoids and Depressive-like Behaviors in Adolescent Rats

Depression is a common mental disorder in adolescents, with a prevalence rate of 5.6%. Current anti-depressive options for adolescents are limited: psychological intervention and conventional antidepressants have low efficacy, a delayed onset of action and increased possibility of suicidal risk. Repetitive transcranial magnetic stimulation (rTMS) as an effective and noninvasive physical therapy for adult depression has been investigated in recent years. However, whether it also produces similar effects on juvenile depression and the underlying mechanism are not clearly understood. In this study, chronic unpredictable mild stress (CMS) was applied to 3-week-old male Sprague Dawley rats for 21 days. Then rTMS was performed for seven consecutive days, and the anti-depressive effects were evaluated by behavioral tests including the sucrose preference test (SPT), the forced swimming test (FST), and the novelty suppressed feeding test (NSF). Expression of hippocampal cannabinoid type I receptor (CB1R), 2-arachidonoylglycerol (2-AG) and relative synthetase and degradative enzymes-diacylglycerol lipase (DAGL) and monoacylglycerol lipase (MAGL) were also investigated. The behavioral parameters were also observed after the administration of the selective CB1 receptor antagonist AM251. The results showed that CMS induced a significant decrease in sucrose preference, a significant increase of immobility time in the FST, and an increased latency to feed in the NSF. In addition, reduced hippocampal CB1 receptor, 2-AG level and increased MAGL protein expression level were also observed in CMS rats. Meanwhile, rTMS treatment upregulated 2-AG level in the hippocampus and ameliorated depressive-like behaviors. The anti-depressive effect of rTMS was attenuated by AM251, a specific CB1R antagonist that was administered 30 min before the onset of rTMS by either intraperitoneal administration or hippocampal microinjection. These results indicate that rTMS can be used as an antidepressive therapy for juvenile depression at least partly mediated by increasing hippocampal 2-AG and CB1 receptor expression levels.

Repetitive transcranial magnetic stimulation for depression after basal ganglia ischaemic stroke: protocol for a multicentre randomised double-blind placebo-controlled trial

INTRODUCTION

Studies suggest that repetitive transcranial magnetic stimulation (rTMS) is effective for the treatment of depression and promotes the repair of white matter. This study aims to assess the effectiveness of rTMS in treating depression after basal ganglia ischaemic stroke and to examine whether such effects are related to restoration of white matter integrity.

METHODS AND ANALYSIS

Sixty-six participants will be recruited from Zhujiang Hospital, Nanfang Hospital and Sichuan Bayi Rehabilitation Hospital and randomised in a 1:1 ratio to receive active rTMS treatment or sham rTMS treatment in addition to routine supportive treatments. The data will be collected at 0, 2 and 4 weeks after the commencement of treatment. The primary outcome is the measurement of 24-item Hamilton Depression Rating Scale scores, and the secondary outcomes include diffusion tensor imaging results and the results of neuropsychological tests including the National Institutes of Health Stroke Scale, Activities of Daily Living Scale, Montreal Cognitive Assessment, Clinical Global Impressions scales, Aphasia Battery in Chinese, Social Support Revalued Scale and Medical Coping Modes Questionnaire.

ETHICS AND DISSEMINATION

This study has been approved by the Ethics Committee of Zhujiang Hospital of Southern Medical University. The findings will be disseminated by publication in a peer-reviewed journal and by presentation at international conferences.

TRIAL REGISTRATION NUMBER

NCT03159351.

Repetitive transcranial magnetic stimulation inhibits Sirt1/MAO-A signaling in the prefrontal cortex in a rat model of depression and cortex-derived astrocytes

Repetitive transcranial magnetic stimulation (rTMS) is a useful monotherapy for depression or adjunctive therapy for resistant depression. However, the anti-depressive effects of different parameters and the underlying mechanisms remain unclear. Here, we aimed to assess the effect of rTMS with different parameters (1/5/10 Hz, 0.84/1.26 T) on the depressive-like behaviors, 5-hydroxytryptamine (5-HT), 5-HIAA (5-hydroxyindoleacetic acid) and DA and NE levels, and monoamine oxidase A (MAO-A) activity in chronic unpredictable stress-treated rats, along with the expression of sirtuin 1 (Sirt1) and MAO-A in the prefrontal cortex (PFC) and cortex-derived astrocytes from new-born rats. Moreover, the depressive-like behaviors were monitored following the transcranial injection of the Sirt1 inhibitor EX527 (1 mM) daily for 1 week. We found that rTMS treatment (5/10 Hz, 0.84/1.26 T) ameliorated depressive-like behaviors, increased 5-HT, DA and NE levels, decreased the 5-HIAA level and Sirt1 and MAO-A expression, and reduced MAO-A activity in the PFC. The depressive-like behaviors were also ameliorated after the transcranial injection of EX527. Importantly, rTMS (5/10 Hz, 0.84/1.26 T) inhibited Sirt1 and MAO-A expressions in astrocytes and Sirt1 knockdown with short hairpin RNA decreased MAO-A expression in astrocytes. These results suggest that the inhibition of Sirt1/MAO-A expression in astrocytes in the PFC may contribute to the different anti-depressive effects of rTMS with different parameters, and may also provide a novel insight into the mechanisms underlying major depressive disorder.

Shuyu capsules relieve liver-qi depression by regulating ERK-CREB-BDNF signal pathway in central nervous system of rat

The purpose of this study was to investigate the possible therapeutic mechanism of Shuyu capsules in liver-qi depression. Liver-qi depression rats were prepared based on chronic unpredictable mild stress (CUMS) and delayed constraint. Rats were gavaged with Shuyu capsule, fluoxetine, Radix Bupleuri and Radix Paeoniae Alba to constrct rat models. Body weight test, sucrose preference test and open-field test were applied to test rat models. Western blot analysis and quantitative real-time PCR was applied to determine the relative expression of extracellular signal-regulated protein kinase (ERK), cyclic AMP response element binding protein (CREB) and brain-derived neurotrophic factor (BDNF) in hippocampus and frontal lobe tissues. ELISA was used to detect the content of BDNF in serum. Body weight, sugar intake and total distance were significantly decreased in depression group compared with control. The four drugs significantly increased levels of these factors. Compared with control group, ERK, CREB and BDNF expression were significantly decreased in depression group in both hippocampus and frontal lobe tissues at both mRNA and protein level. Shuyu capsule and fluoxetine group showed a significant increase in the expression of ERK, CREB and BDNF at mRNA, p-ERK and p-BDNF at protein level. Compared with Radix Paeoniae Alba, Radix Bupleuri were better in the rescue of ERK, CREB and BDNF expression. In conclusion, the pathogenesis of liver-qi depression associated with lower expression of ERK, CREB and BDNF in hippocampus and frontal. Shuyu capsule and main constitution alleviated the depressive-like behaviors and reversed the disruptions of the p-ERK, p-CREB and BDNF in stressed rats.

Xiaochaihutang attenuates depressive/anxiety-like behaviors of social isolation-reared mice by regulating monoaminergic system, neurogenesis and BDNF expression

ETHNOPHARMACOLOGICAL RELEVANCE

Xiaochaihutang (XCHT), as a classical herbal formula for the treatment of "Shaoyang syndrome" has been demonstrated to exert an antidepressant effect in multiple animal models of depression as shown in our previous studies. However, the effects of XCHT on social isolation (SI)-reared mice have not been investigated. This study aims to explore the effects of XCHT on depressive/anxiety-like behaviors of SI-reared mice, and its implicated mechanisms, including alterations in the monoaminergic system, neurogenesis and neurotrophin expression.

MATERIALS AND METHODS

Male C57 BL/6J mice (aged 4 weeks after weaning) were reared isolatedly for 8 weeks and XCHT (0.8, 2.3, 7.0g/kg) were given by gavage once a day. Forced swimming test (FST), tail suspension test (TST), open field test (OFT), elevated-plus maze test (EPM) and intruder-induced aggression test were used to explore the effects of XCHT on depressive/anxiety-like behaviors of SI-reared mice after administration of XCHT for 6 weeks. HPLC-MS/MS was performed to quantify the levels of neurotransmitters in the hippocampus by in vivo microdialysis, while western immunoblotting was used to evaluate the action of XCHT on the synthesis, transport and degradation of monoamine neurotransmitters. Immunofluorescence was used to study the effects of XCHT on neurogenesis and neurotrophin expression, including Ki-67, DCX, BrdU and BDNF.

RESULTS

Our results showed that administration of XCHT (0.8, 2.3 and 7.0g/kg) for 6 weeks significantly attenuated the increase in immobility time in TST and FST, improved the anxiety-like behaviors in OFT and EPM, and improved the aggressive behaviors of SI-reared mice. XCHT significantly elevated monoamine neurotransmitters levels and inhibited 5-HT turnover (5-HIAA/5-HT) in hippocampal microdialysates of SI-reared mice. In addition, we found XCHT enhanced monoamine neurotransmitter synthesis enzymes (TPH2 and TH) expressions, inhibited serotonin transporter (SERT) expression and decreased monoamine neurotransmitter degradation enzyme (MAO_A) expression in the hippocampus of SI-reared mice for the first time. Moreover, XCHT significantly augmented hippocampal neurogenesis and BDNF expression in hippocampus of SI-reared mice.

CONCLUSIONS

Our results showed for the first time that XCHT improved depressive/anxiety-like behaviors of SI-reared mice by regulating the monoaminergic system, neurogenesis and neurotrophin expression. The findings indicate that XCHT may have a therapeutic application for early-life stress model of depression and in turn provide further evidence supporting XCHT a novel potential antidepressant from a distinct perspective.

A Pulsed Electromagnetic Field Protects against Glutamate-Induced Excitotoxicity by Modulating the Endocannabinoid System in HT22 Cells

Glutamate-induced excitotoxicity is common in the pathogenesis of many neurological diseases. A pulsed electromagnetic field (PEMF) exerts therapeutic effects on the nervous system, but its specific mechanism associated with excitotoxicity is still unknown. We investigated the role of PEMF exposure in regulating glutamate-induced excitotoxicity through the endocannabinoid (eCB) system. PEMF exposure improved viability of HT22 cells after excitotoxicity and reduced lactate dehydrogenase release and cell death. An eCB receptor 1 (CB1R) specific inhibitor suppressed the protective effects of PEMF exposure, even though changes in CB1R expression were not observed. Elevation of N-arachidonylethanolamide (AEA) and 2-arachidonylglycerol (2-AG) following PEMF exposure indicated that the neuroprotective effects of PEMF were related to modulation of the eCB metabolic system. Furthermore, CB1R/ERK signaling was shown to be an important downstream pathway of PEMF in regulating excitotoxicity. These results suggest that PEMF exposure leads to neuroprotective effects against excitotoxicity by facilitating the eCB/CB1R/ERK signaling pathway. Therefore, PEMF may be a potential physical therapeutic technique for preventing and treating neurological diseases.

The chronic mild stress (CMS) model of depression: History, evaluation and usage

Now 30 years old, the chronic mild stress (CMS) model of depression has been used in >1300 published studies, with a year-on-year increase rising to >200 papers in 2015. Data from a survey of users show that while a variety of names are in use (chronic mild/unpredictable/varied stress), these describe essentially the same procedure. This paper provides an update on the validity and reliability of the CMS model, and reviews recent data on the neurobiological basis of CMS effects and the mechanisms of antidepressant action: the volume of this research may be unique in providing a comprehensive account of antidepressant action within a single model. Also discussed is the use of CMS in drug discovery, with particular reference to hippocampal and extra-hippocampal targets. The high translational potential of the CMS model means that the neurobiological mechanisms described may be of particular relevance to human depression and mechanisms of clinical antidepressant action.

Anti-Apoptotic Protein Bcl-xL Expression in the Midbrain Raphe Region Is Sensitive to Stress and Glucocorticoids

Anti-apoptotic proteins are suggested to be important for the normal health of neurons and synapses as well as for resilience to stress. In order to determine whether stressful events may influence the expression of anti-apoptotic protein Bcl-xL in the midbrain and specifically in the midbrain serotonergic (5-HT) neurons involved in neurobehavioral responses to adverse stimuli, adult male rats were subjected to short-term or chronic forced swim stress. A short-term stress rapidly increased the midbrain bcl-xl mRNA levels and significantly elevated Bcl-xL immunoreactivity in the midbrain 5-HT cells. Stress-induced increase in glucocorticoid secretion was implicated in the observed effect. The levels of bcl-xl mRNA were decreased after stress when glucocorticoid elevation was inhibited by metyrapone (MET, 150 mg/kg), and this decrease was attenuated by glucocorticoid replacement with dexamethasone (DEX; 0.2 mg/kg). Both short-term stress and acute DEX administration, in parallel with Bcl-xL, caused a significant increase in tph2 mRNA levels and slightly enhanced tryptophan hydroxylase immunoreactivity in the midbrain. The increasing effect on the bcl-xl expression was specific to the short-term stress. Forced swim repeated daily for 2 weeks led to a decrease in bcl-xl mRNA in the midbrain without any effects on the Bcl-xL protein expression in the 5-HT neurons. In chronically stressed animals, an increase in tph2 gene expression was not associated with any changes in tryptophan hydroxylase protein levels. Our findings are the first to demonstrate that both short-term stress and acute glucocorticoid exposures induce Bcl-xL protein expression in the midbrain 5-HT neurons concomitantly with the activation of the 5-HT synthesis pathway in these neurons.

The Effects of Different Repetitive Transcranial Magnetic Stimulation (rTMS) Protocols on Cortical Gene Expression in a Rat Model of Cerebral Ischemic-Reperfusion Injury

Although repetitive Transcranial Magnetic Stimulation (rTMS) in treatment of stroke in humans has been explored over the past decade the data remain controversial in terms of optimal stimulation parameters and the mechanisms of rTMS long-term effects. This study aimed to explore the potential of different rTMS protocols to induce changes in gene expression in rat cortices after acute ischemic-reperfusion brain injury. The stroke was induced by middle cerebral artery occlusion (MCAO) with subsequent reperfusion. Changes in the expression of 96 genes were examined using low-density expression arrays after MCAO alone and after MCAO combined with 1Hz, 5Hz, continuous (cTBS) and intermittent (iTBS) theta-burst rTMS. rTMS over the lesioned hemisphere was given for two weeks (with a 2-day pause) in a single daily session and a total of 2400 pulses. MCAO alone induced significant upregulation in the expression of 44 genes and downregulation in 10. Two weeks of iTBS induced significant increase in the expression of 52 genes. There were no downregulated genes. 1Hz and 5Hz had no significant effects on gene expression, while cTBS effects were negligible. Upregulated genes included those involved in angiogenesis, inflammation, injury response and cellular repair, structural remodeling, neuroprotection, neurotransmission and neuronal plasticity. The results show that long-term rTMS in acute ischemic-reperfusion brain injury induces complex changes in gene expression that span multiple pathways, which generally promote the recovery. They also demonstrate that induced changes primarily depend on the rTMS frequency (1Hz and 5Hz vs. iTBS) and pattern (cTBS vs. iTBS). The results further underlines the premise that one of the benefits of rTMS application in stroke may be to prime the brain, enhancing its potential to cope with the injury and to rewire. This could further augment its potential to favorably respond to rehabilitation, and to restore some of the loss functions.

Treatment-resistant depression: are animal models of depression fit for purpose?

BACKGROUND

Resistance to antidepressant drug treatment remains a major health problem. Animal models of depression are efficient in detecting effective treatments but have done little to increase the reach of antidepressant drugs. This may be because most animal models of depression target the reversal of stress-induced behavioural change, whereas treatment-resistant depression is typically associated with risk factors that predispose to the precipitation of depressive episodes by relatively low levels of stress. Therefore, the search for treatments for resistant depression may require models that incorporate predisposing factors leading to heightened stress responsiveness.

METHOD

Using a diathesis-stress framework, we review developmental, genetic and genomic models against four criteria: (i) increased sensitivity to stress precipitation of a depressive behavioural phenotype, (ii) resistance to chronic treatment with conventional antidepressants, (iii) a good response to novel modes of antidepressant treatment (e.g. ketamine; deep brain stimulation) that are reported to be effective in treatment-resistant depression and (iv) a parallel to a known clinical risk factor.

RESULTS

We identify 18 models that may have some potential. All require further validation. Currently, the most promising are the Wistar-Kyoto (WKY) and congenital learned helplessness (cLH) rat strains, the high anxiety behaviour (HAB) mouse strain and the CB1 receptor knockout and OCT2 null mutant mouse strains.

CONCLUSION

Further development is needed to validate models of antidepressant resistance that are fit for purpose. The criteria used in this review may provide a helpful framework to guide research in this area.

Quetiapine and repetitive transcranial magnetic stimulation ameliorate depression-like behaviors and up-regulate the proliferation of hippocampal-derived neural stem cells in a rat model of depression: The involvement of the BDNF/ERK signal pathway

Quetiapine (QUE) and repetitive transcranial magnetic stimulation (rTMS) have been considered to be possible monotherapies for depression or adjunctive therapies for the treatment of the resistant depression, but the underlying mechanisms remain unclear. The present study aimed to assess the effects of combined QUE and rTMS treatment on depressive-like behaviors, hippocampal proliferation, and the in vivo and in vitro expressions of phosphorylated extracellular signal-regulated protein kinase (pERK1/2) and brain-derived neurotrophic factor (BDNF) in male Sprague-Dawley rats. The administration of QUE and rTMS was determined not only to reverse the depressive-like behaviors of rats exposed to chronic unpredictable stress (CUS) but also to restore the protein expressions of pERK1/2 and BDNF and cell proliferation in the hippocampus. Additionally, QUE and rTMS promoted the proliferation and increased the expression of pERK1/2 and BDNF in hippocampal-derived neural stem cells (NSCs), and these effects were abolished by U0126. Taken together, these results suggest that the antidepressive-like effects of QUE and rTMS might be related to the activation of the BDNF/ERK signaling pathway and the up-regulation of cell proliferation in the hippocampus.