Long-lasting effects of chronic rTMS to treat chronic rodent model of depression

Status and trends of TMS research in depressive disorder: a bibliometric and visual analysis

Background

Depression is a chronic psychiatric condition that places significant burdens on individuals, families, and societies. The rapid evolution of non-invasive brain stimulation techniques has facilitated the extensive clinical use of Transcranial Magnetic Stimulation (TMS) for depression treatment. In light of the substantial recent increase in related research, this study aims to employ bibliometric methods to systematically review the global research status and trends of TMS in depression, providing a reference and guiding future studies in this field.

Methods

We retrieved literature on TMS and depression published between 1999 and 2023 from the Science Citation Index Expanded (SCIE) and Social Science Citation Index (SSCI) databases within the Web of Science Core Collection (WoSCC). Bibliometric analysis was performed using VOSviewer and CiteSpace software to analyze data on countries, institutions, authors, journals, keywords, citations, and to generate visual maps.

Results

A total of 5,046 publications were extracted covering the period from 1999 to 2023 in the field of TMS and depression. The publication output exhibited an overall exponential growth trend. These articles were published across 804 different journals, BRAIN STIMULATION is the platform that receives the most articles in this area. The literature involved contributions from over 16,000 authors affiliated with 4,573 institutions across 77 countries. The United States contributed the largest number of publications, with the University of Toronto and Daskalakis ZJ leading as the most prolific institution and author, respectively. Keywords such as "Default Mode Network," "Functional Connectivity," and "Theta Burst" have recently garnered significant attention. Research in this field primarily focuses on TMS stimulation patterns, their therapeutic efficacy and safety, brain region and network mechanisms under combined brain imaging technologies, and the modulation effects of TMS on brain-derived neurotrophic factor (BDNF) and neurotransmitter levels.

Conclusion

In recent years, TMS therapy has demonstrated extensive potential applications and significant implications for the treatment of depression. Research in the field of TMS for depression has achieved notable progress. Particularly, the development of novel TMS stimulation patterns and the integration of TMS therapy with multimodal techniques and machine learning algorithms for precision treatment and investigation of brain network mechanisms have emerged as current research hotspots.

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.

The impact of adult neurogenesis on affective functions: of mice and men

In most mammals, new neurons are not only produced during embryogenesis but also after birth. Soon after adult neurogenesis was discovered, the influence of recruiting new neurons on cognitive functions, especially on memory, was documented. Likewise, the late process of neuronal production also contributes to affective functions, but this outcome was recognized with more difficulty. This review covers hypes and hopes of discovering the influence of newly-generated neurons on brain circuits devoted to affective functions. If the possibility of integrating new neurons into the adult brain is a commonly accepted faculty in the realm of mammals, the reluctance is strong when it comes to translating this concept to humans. Compiling data suggest now that new neurons are derived not only from stem cells, but also from a population of neuroblasts displaying a protracted maturation and ready to be engaged in adult brain circuits, under specific signals. Here, we discuss the significance of recruiting new neurons in the adult brain circuits, specifically in the context of affective outcomes. We also discuss the fact that adult neurogenesis could be the ultimate cellular process that integrates elements from both the internal and external environment to adjust brain functions. While we must be critical and beware of the unreal promises that Science could generate sometimes, it is important to continue exploring the potential of neural recruitment in adult primates. Reporting adult neurogenesis in humankind contributes to a new vision of humans as mammals whose brain continues to develop throughout life. This peculiar faculty could one day become the target of treatment for mental health, cognitive disorders, and elderly-associated diseases. The vision of an adult brain which never stops integrating new neurons is a real game changer for designing new therapeutic interventions to treat mental disorders associated with substantial morbidity, mortality, and social costs.

Combinatorial strategies for cell transplantation in traumatic spinal cord injury

Spinal cord injury (SCI) substantially reduces the quality of life of affected individuals. Recovery of function is therefore a primary concern of the patient population and a primary goal for therapeutic interventions. Currently, even with growing numbers of clinical trials, there are still no effective treatments that can improve neurological outcomes after SCI. A large body of work has demonstrated that transplantation of neural stem/progenitor cells (NSPCs) can promote regeneration of the injured spinal cord by providing new neurons that can integrate into injured host neural circuitry. Despite these promising findings, the degree of functional recovery observed after NSPC transplantation remains modest. It is evident that treatment of such a complex injury cannot be addressed with a single therapeutic approach. In this mini-review, we discuss combinatorial strategies that can be used along with NSPC transplantation to promote spinal cord regeneration. We begin by introducing bioengineering and neuromodulatory approaches, and highlight promising work using these strategies in integration with NSPCs transplantation. The future of NSPC transplantation will likely include a multi-factorial approach, combining stem cells with biomaterials and/or neuromodulation as a promising treatment for SCI.

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.

Neuroimaging and serum biomarkers of neurodegeneration and neuroplasticity in Parkinson's disease patients treated by intermittent theta-burst stimulation over the bilateral primary motor area: a randomized, double-blind, sham-controlled, crossover trial study

Background and objectives

Intermittent theta-burst stimulation (iTBS) is a patterned form of excitatory transcranial magnetic stimulation that has yielded encouraging results as an adjunctive therapeutic option to alleviate the emergence of clinical deficits in Parkinson's disease (PD) patients. Although it has been demonstrated that iTBS influences dopamine-dependent corticostriatal plasticity, little research has examined the neurobiological mechanisms underlying iTBS-induced clinical enhancement. Here, our primary goal is to verify whether iTBS bilaterally delivered over the primary motor cortex (M1) is effective as an add-on treatment at reducing scores for both motor functional impairment and nonmotor symptoms in PD. We hypothesize that these clinical improvements following bilateral M1-iTBS could be driven by endogenous dopamine release, which may rebalance cortical excitability and restore compensatory striatal volume changes, resulting in increased striato-cortico-cerebellar functional connectivity and positively impacting neuroglia and neuroplasticity.

Methods

A total of 24 PD patients will be assessed in a randomized, double-blind, sham-controlled crossover study involving the application of iTBS over the bilateral M1 (M1 iTBS). Patients on medication will be randomly assigned to receive real iTBS or control (sham) stimulation and will undergo 5 consecutive sessions (5 days) of iTBS over the bilateral M1 separated by a 3-month washout period. Motor evaluation will be performed at different follow-up visits along with a comprehensive neurocognitive assessment; evaluation of M1 excitability; combined structural magnetic resonance imaging (MRI), resting-state electroencephalography and functional MRI; and serum biomarker quantification of neuroaxonal damage, astrocytic reactivity, and neural plasticity prior to and after iTBS.

Discussion

The findings of this study will help to clarify the efficiency of M1 iTBS for the treatment of PD and further provide specific neurobiological insights into improvements in motor and nonmotor symptoms in these patients. This novel project aims to yield more detailed structural and functional brain evaluations than previous studies while using a noninvasive approach, with the potential to identify prognostic neuroprotective biomarkers and elucidate the structural and functional mechanisms of M1 iTBS-induced plasticity in the cortico-basal ganglia circuitry. Our approach may significantly optimize neuromodulation paradigms to ensure state-of-the-art and scalable rehabilitative treatment to alleviate motor and nonmotor symptoms of PD.

Repetitive Transcranial Magnetic Stimulation Reduces Depressive-like Behaviors, Modifies Dendritic Plasticity, and Generates Global Epigenetic Changes in the Frontal Cortex and Hippocampus in a Rodent Model of Chronic Stress

Depression is the most common affective disorder worldwide, accounting for 4.4% of the global population, a figure that could increase in the coming decades. In depression, there exists a reduction in the availability of dendritic spines in the frontal cortex (FC) and hippocampus (Hp). In addition, histone modification and DNA methylation are also dysregulated epigenetic mechanisms in depression. Repetitive transcranial magnetic stimulation (rTMS) is a technique that is used to treat depression. However, the epigenetic mechanisms of its therapeutic effect are still not known. Therefore, in this study, we evaluated the antidepressant effect of 5 Hz rTMS and examined its effect on dendritic remodeling, immunoreactivity of synapse proteins, histone modification, and DNA methylation in the FC and Hp in a model of chronic mild stress. Our data indicated that stress generated depressive-like behaviors and that rTMS reverses this effect, romotes the formation of dendritic spines, and favors the presynaptic connection in the FC and DG (dentate gyrus), in addition to increasing histone H3 trimethylation and DNA methylation. These results suggest that the antidepressant effect of rTMS is associated with dendritic remodeling, which is probably regulated by epigenetic mechanisms. These data are a first approximation of the impact of rTMS at the epigenetic level in the context of depression. Therefore, it is necessary to analyze in future studies as to which genes are regulated by these mechanisms, and how they are associated with the neuroplastic modifications promoted by rTMS.

Repetitive transcranial magnetic stimulation and fluoxetine reverse depressive-like behavior but with differential effects on Olig2-positive cells in chronically stressed mice

Depression is a mood disorder coursing with several behavioral, cellular, and neurochemical alterations. The negative impact of chronic stress may precipitate this neuropsychiatric disorder. Interestingly, downregulation of oligodendrocyte-related genes, abnormal myelin structure, and reduced numbers and density of oligodendrocytes in the limbic system have been identified in patients diagnosed with depression, but also in rodents exposed to chronic mild stress (CMS). Several reports have emphasized the importance of pharmacological or stimulation-related strategies in influencing oligodendrocytes in the hippocampal neurogenic niche. Repetitive transcranial magnetic stimulation (rTMS) has gained attention as an intervention to revert depression. Here, we hypothesized that 5 Hz (Hz) of rTMS or Fluoxetine (Flx) would revert depressive-like behaviors by influencing oligodendrocytes and revert neurogenic alterations caused by CMS in female Swiss Webster mice. Our results showed that 5 Hz rTMS or Flx revert depressive-like behavior. Only rTMS influenced oligodendrocytes by increasing the number of Olig2-positive cells in the hilus of the dentate gyrus and the prefrontal cortex. However, both strategies exerted effects on some events of the hippocampal neurogenic processes, such as cell proliferation (Ki67-positive cells), survival (CldU-positive cells), and intermediate stages (doublecortin-positive cells) along the dorsal-ventral axis of this region. Interestingly, the combination of rTMS-Flx exerted antidepressant-like effects, but the increased number of Olig2-positive cells observed in mice treated only with rTMS was canceled. However, rTMS-Flx exerted a synergistic effect by increasing the number of Ki67-positive cells. It also increased the number of CldU- and doublecortin-positive cells in the dentate gyrus. Our results demonstrate that 5 Hz rTMS has beneficial effects, as it reverted depressive-like behavior by increasing the number of Olig2-positive cells and reverting the decrement in hippocampal neurogenesis in CMS-exposed mice. Nevertheless, the effects of rTMS on other glial cells require further investigation.

Repetitive transcranial magnetic stimulation promotes neurological functional recovery in rats with traumatic brain injury by upregulating synaptic plasticity-related proteins

Studies have shown that repetitive transcranial magnetic stimulation (rTMS) can enhance synaptic plasticity and improve neurological dysfunction. However, the mechanism through which rTMS can improve moderate traumatic brain injury remains poorly understood. In this study, we established rat models of moderate traumatic brain injury using Feeney’s weight-dropping method and treated them using rTMS. To help determine the mechanism of action, we measured levels of several important brain activity-related proteins and their mRNA. On the injured side of the brain, we found that rTMS increased the protein levels and mRNA expression of brain-derived neurotrophic factor, tropomyosin receptor kinase B, N-methyl-D-aspartic acid receptor 1, and phosphorylated cAMP response element binding protein, which are closely associated with the occurrence of long-term potentiation. rTMS also partially reversed the loss of synaptophysin after injury and promoted the remodeling of synaptic ultrastructure. These findings suggest that upregulation of synaptic plasticity-related protein expression is the mechanism through which rTMS promotes neurological function recovery after moderate traumatic brain injury.

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.

Leaves of Cedrela sinensis Attenuate Chronic Unpredictable Mild Stress-Induced Depression-like Behavior via Regulation of Hormonal and Inflammatory Imbalance

This study aimed to evaluate the protective effects of ethyl acetate fraction from Cedrela sinensis (EFCS) against chronic unpredictable mild stress (CUMS)-induced behavioral dysfunction and stress response in C57BL/6 mice. The physiological compounds of EFCS were identified as rutin, isoquercitrin, ethyl gallate, quercitrin, kaempferol-3-O-rhamnoside, and ethyl digallate, using UPLC-Q-TOF/MS^E. To evaluate the neuroprotective effect of EFCS, H₂O₂^- and corticosterone-induced neuronal cell viability was conducted in human neuroblastoma MC-IXC cells. It was found that EFCS alleviated depression-like behavior by conducting the sucrose preference test (SPT), forced swimming test (FST), open field test (OFT), and tail suspension test (TST). EFCS inhibited mitochondrial dysfunction related to neuronal energy metabolism by regulating reactive oxygen species (ROS) levels, mitochondrial membrane potential (MMP), and ATP contents in brain tissue. In addition, the administration of EFCS regulated the stress hormones in serum. EFCS regulated stress-related indicators such as CRF, ACTH, CYP11B1, and BDNF. Moreover, EFCS downregulated the inflammatory responses and apoptosis proteins such as caspase-1, TNF-α, IL-1β, p-JNK, BAX, and p-tau in brain tissues. These results suggest that EFCS might be a potential natural plant material that alleviates CUMS-induced behavior disorder by regulating inflammation in brain tissue against CUMS-induced depression.

Resveratrol Ameliorates Trigeminal Neuralgia-Induced Cognitive Deficits by Regulating Neural Ultrastructural Remodelling and the CREB/BDNF Pathway in Rats

Chronic pain often leads to cognitive impairment. Resveratrol (Res), a natural polyphenol existing in Polygonum cuspidatum, has been widely investigated for its antinociceptive, anti-inflammatory, and neuroprotective properties. Our aim was to explore the ameliorating effects of resveratrol on pain-related behaviors and learning and memory deficits induced by cobra venom-induced trigeminal neuralgia (TN). The TN model of rats was established by injecting cobra venom solution beneath the epineurium of the infraorbital nerve. Resveratrol was intragastrically administered at a dose of 40 mg/kg twice daily beginning on postoperative day 15. CREB inhibitor 666-15 was intraperitoneally administered at a dose of 10 mg/kg from POD 35-42 after morning resveratrol treatment. Mechanical allodynia was measured via von Frey filaments. Rat free movement was videotaped and analyzed. Spatial learning and memory were evaluated via the Morris water maze test. Ultrastructures of the hippocampal DG region and infraorbital nerve were observed by transmission electron microscopy. We found that resveratrol alleviated TN-induced allodynia, ameliorated learning and memory deficits, restored the ultrastructure of hippocampal neurons and synapses, repaired the damaged myelin sheath of the infraorbital nerve, and activated the CREB/BDNF pathway in the hippocampus of TN rats. CREB inhibitor administration suppressed the resveratrol-rescued abnormal hippocampal ultrastructural changes and aggravated spatial learning and memory impairment by inhibiting CREB/BDNF pathway activation in the hippocampus. Our findings indicated that resveratrol alleviated pain and improved cognitive deficits, probably by regulating neural ultrastructure remodelling and the CREB/BDNF pathway.

Improving Upper Limb and Gait Rehabilitation Outcomes in Post-Stroke Patients: A Scoping Review on the Additional Effects of Non-Invasive Brain Stimulation When Combined with Robot-Aided Rehabilitation

Robot-aided rehabilitation (RAR) and non-invasive brain stimulation (NIBS) are the two main interventions for post-stroke rehabilitation. The efficacy of both approaches in combination has not been well established yet. The importance of coupling these interventions, which both enhance brain plasticity to promote recovery, lies in augmenting the rehabilitation potential to constrain the limitation in daily living activities and the quality of life following stroke. This review aimed to evaluate the evidence of NIBS coupled with RAR in improving rehabilitation outcomes of upper limb and gait motor impairment in adult individuals with stroke. We included 18 clinical trials in this review. All studies were highly heterogeneous concerning the technical characteristics of robotic devices and NIBS protocols. However, the studies reported a global improvement in body structure and function and activity limitation for the upper limb, which were non-significant between the active and control groups. Concerning gait training protocols, the active group outperformed the control group in improving walking capacity and recovery. According to this review, NIBS and RAR in combination are promising but not yet largely recommendable as a systematic approach for stroke rehabilitation as there is not enough data about this. Therefore, more homogenous clinical trials are required, pointing out the best characteristics of the combined therapeutic protocols.

Encore: Behavioural animal models of stress, depression and mood disorders

Animal studies over the past two decades have led to extensive advances in our understanding of pathogenesis of depressive and mood disorders. Among these, rodent behavioural models proved to be of highest informative value. Here, we present a comprehensive overview of the most popular behavioural models with respect to physiological, circuit, and molecular biological correlates. Behavioural stress paradigms and behavioural tests are assessed in terms of outcomes, strengths, weaknesses, and translational value, especially in the domain of pharmacological studies.

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.

Benefits from Repetitive Transcranial Magnetic Stimulation in Post-Stroke Rehabilitation

Stroke is an acute neurovascular central nervous system (CNS) injury and one of the main causes of long-term disability and mortality. Post-stroke rehabilitation as part of recovery is focused on relearning lost skills and regaining independence as much as possible. Many novel strategies in neurorehabilitation have been introduced. This review focuses on current evidence of the effectiveness of repetitive transcranial magnetic stimulation (rTMS), a noninvasive brain stimulation (NIBS), in post-stroke rehabilitation. Moreover, we present the effects of specific interventions, such as low-frequency or high-frequency rTMS therapy, on motor function, cognitive function, depression, and aphasia in post-stroke patients. Collected data suggest that high-frequency stimulation (5 Hz and beyond) produces an increase in cortical excitability, whereas low-frequency stimulation (≤1 Hz) decreases cortical excitability. Accumulated data suggest that rTMS is safe and can be used to modulate cortical excitability, which may improve overall performance. Side effects such as tingling sensation on the skin of the skull or headache are possible. Serious side effects such as epileptic seizures can be avoided by adhering to international safety guidelines. We reviewed clinical studies that present promising results in general recovery and stimulating neuroplasticity. This article is an overview of the current rTMS state of knowledge related to benefits in stroke, as well as its cellular and molecular mechanisms. In the stroke rehabilitation literature, there is a key methodological problem of creating double-blinding studies, which are very often impossible to conduct.

The Preventive and Therapeutic Effect of Repetitive Transcranial Magnetic Stimulation on Radiation-Induced Brain Injury in Mice

PURPOSE

To clarify the preventive and therapeutic effects of repetitive transcranial magnetic stimulation (rTMS) on brain injury induced by X-ray cranial irradiation, preliminarily identify the mechanism and provide a novel clinical approach for the prevention and treatment of radiation-induced brain injury (RBI).

MATERIALS AND METHODS

Male C57BL/6 mice were randomly divided into the sham group, large fractionated dose (5 Gy ×4 d) group, large fractionated dose + rTMS (5 Gy ×4 d + rTMS) group, conventional fractionated dose (2 Gy ×10 d) group and conventional fractionated dose + rTMS (2 Gy ×10 d + rTMS) group. After cranial irradiation and rTMS, behavioral experiments, morphological staining and molecular biology experiments were performed. We further determined the mechanism of rTMS on the prevention and treatment of RBI, including changes in hippocampal neuronal apoptosis, neural stem cell (NSC) proliferation and differentiation, and neuronal synaptic plasticity.

RESULTS

rTMS alleviated the negative effects of cranial radiation on the general health of mice and promoted their recovery. rTMS ameliorated the impairment of spatial learning and memory induced by cranial radiation, and this beneficial effect was more robust in the conventional fractionated dose group than the large fractionated dose group. Moreover, rTMS alleviated the alterations in hippocampal structure and neuronal death and had preventive and therapeutic effects against RBI. In addition, rTMS reduced hippocampal cell apoptosis, promoted NSC proliferation and differentiation in the hippocampus after cranial irradiation, and enhanced neuronal synaptic plasticity in the hippocampus. Subsequent studies showed that rTMS upregulated the expression of learning- and memory-related proteins.

CONCLUSION

rTMS could alleviate learning and memory impairment caused by RBI, and the preventive and therapeutic effects of rTMS were better for the conventional fraction radiation paradigms.

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.

Adolescent neuroimmune function and its interaction with alcohol

Adolescence is an evolutionarily conserved developmental period associated with behavioral change, including increased risk-taking and alcohol use. Experimentation with alcohol typically begins in adolescence and transitions to binge-like patterns of consumption. Alcohol exposure during adolescence can alter normative changes in brain structure and function. Understanding mechanisms by which ethanol impacts neurodevelopmental processes is important for preventing and ameliorating the deleterious consequences of adolescent alcohol abuse. This review focuses on the neuroimmune system as a key contributor to ethanol-induced changes in adolescent brain and behavior. After brief review of neuroimmune system development, acute and chronic effects of ethanol on adolescent neuroimmune functioning are addressed. Comparisons between stress/immunological challenges and ethanol on adolescent neuroimmunity are reviewed, as cross-sensitization is relevant during adolescence. The mechanisms by which ethanol alters neuroimmune functioning are then discussed, as they may portend development of neuropathological consequences and thus increase vulnerability to subsequent challenges and potentiate addictive behaviors.

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.

Treatment of postoperative delirium with continuous theta burst stimulation: study protocol for a randomised controlled trial

INTRODUCTION

Postoperative delirium is one of the most common postoperative complications among elderly patients (65 years old or older). However, there are no effective treatments for this condition. Recent research suggests that continuous theta burst stimulation (cTBS), a non-invasive brain stimulation, can reduce pain level, improve cognitive function and affective symptoms in multiple diseases or dysfunctions, including anxiety disorders, major depressive disorder, sleep disorders and pain. But the potential benefits of cTBS in reducing postoperative delirium have not been investigated. Therefore, we propose determining whether cTBS can prevent and/or treat postoperative delirium in senior patients.

METHODS AND ANALYSIS

The study will be a double-blind, randomised controlled trial. Participants (65 years old or older) undergoing scheduled orthopaedic surgery (≥2 hours, general anaesthesia) will be randomised to receive either cTBS or sham stimulation with a focal figure-of-eight coil over the right dorsolateral prefrontal cortex at 80% of the resting motor threshold. Every patient will receive 2-3 sets of stimulations during postoperative days (40 s per session, 3 sessions per set, 1 set per day). Participants will be assessed twice daily by a research assistant blinded to allocation. The primary outcome will be the incidence of postoperative delirium measured by the Confusion Assessment Method on postoperative days 1, 2 and 3. The secondary outcomes will be the severity and duration of postoperative delirium, cognitive function, pain, sleep quality, activities of daily living, length of hospital stay, discharge-to-facility or home, and rate of complication and mortality during the hospital stay.

ETHICS AND DISSEMINATION

Ethical approval has been obtained from the ethics committee of Shanghai 10th People's Hospital. The principal investigator will submit a research progress report to the ethics committee regularly. All participants will provide written informed consent. Study results will be published in a peer-reviewed journal.

TRIAL REGISTRATION NUMBER

NCT04661904.

Moving back in the brain to drive the field forward: Targeting neurostimulation to different brain regions in animal models of depression and neurodegeneration

BACKGROUND

Repetitive transcranial magnetic stimulation is a promising noninvasive therapeutic tool for a variety of brain-related disorders. However, most therapeutic protocols target the anterior regions, leaving many other areas unexplored. There is a substantial therapeutic potential for stimulating various brain regions, which can be optimized in animal models.

NEW METHOD

We illustrate a method that can be utilized reliably to stimulate the anterior or posterior brain in freely moving rodents. A coil support device is surgically attached onto the skull, which is used for consistent coil placement over the course of up to several weeks of stimulation sessions.

RESULTS

Our methods provide reliable stimulation in animals without the need for restraint or sedation. We see little aversive effects of support placement and stimulation. Computational models provide evidence that moving the coil support location can be utilized to target major stimulation sites in humans and mice.

SUMMARY OF FINDINGS WITH THIS METHOD

Animal models are key to optimizing brain stimulation parameters, but research relies on restraint or sedation for consistency in coil placement. The method described here provides a unique means for reliable targeted stimulation in freely moving animals. Research utilizing this method has uncovered changes in biochemical and animal behavioral measurements as a function of brain stimulation.

CONCLUSIONS

The majority of research on magnetic stimulation focuses on anterior regions. Given the substantial network connectivity throughout the brain, it is critical to develop a reliable method for stimulating different regions. The method described here can be utilized to better inform clinical trials about optimal treatment localization, stimulation intensity and number of treatment sessions, and provides a motivation for exploring posterior brain regions for both mice and humans.

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.

Prenatal ethanol exposure increases susceptibility to depression- and anxiety-like behavior in adult female offspring and its underlying mechanism

Epidemiological investigations have found that maternal alcohol intake increases the risk of mental illness in offspring. Our study investigated changes of depression- and anxiety-like behaviors in adult offspring caused by prenatal ethanol exposure (PEE) and explored the potential mechanism. After Wistar rats were intragastrically administered ethanol at a dose of 4 g/kg·d on the 9-20 t h days of pregnancy, the offspring were given 21 days of chronic unpredictable mild stress (CUMS) starting from the 9th week after birth. Before CUMS, the behavioral results showed that the PEE offspring appeared excited and anxious. After CUMS, the PEE offspring rats were more sensitive to the same intensity of stimulation, and then the behavioral disorders aggravated. In adult offspring from the PEE group, the intercellular space was enlarged in the hippocampus, and there was a loss of pyramidal cells. The expression of brain-derived neurotrophic factor (BDNF) decreased; the mRNA expression of the glucocorticoid receptor and synaptic plasticity-related genes decreased; the apoptosis-related genes expressed disrupted. In order to determine whether hippocampal injury and dysfunction resulted from ethanol directly or indirectly, we performed in vitro study. The outcome was accompanied by disrupted gene expression related to neurogenesis and synaptic plasticity. PEE increases the susceptibility of adult female offspring to depression- and anxiety-like behaviors, and its mechanism may be related to the toxic effects of ethanol, both directly and indirectly. The latter inhibits the hippocampal BDNF pathway, leading to the disruption of hippocampal neurogenesis, apoptosis and decreased synaptic plasticity.

Antidepressant efficacy and immune effects of bilateral theta burst stimulation monotherapy in major depression: A randomized, double-blind, sham-controlled study

Inflammation theory has been consolidated by accumulating evidence, and many studies have suggested that the peripheral cytokine levels could be biomarkers for disease status and treatment outcome in major depressive disorder (MDD). Theta burst stimulation (TBS), a new form of repetitive transcranial magnetic stimulation (TMS) for MDD, has been demonstrated to improve depression via modulating dysfunctional neural network or hypothalamic–pituitary–adrenal axis hyperactivities in MDD. However, there is lack of exploratory studies investigating its effect on serum inflammatory cytokines. Here, we aimed to investigate the antidepressant efficacy of bilateral TBS monotherapy and its effects on the serum cytokine levels in MDD. We conducted a double-blind, randomized, sham-controlled trial, with 53 MDD patients who exhibited no responses to at least one adequate antidepressant treatment for the prevailing episode assigned randomly to one of two groups: bilateral TBS monotherapy (n = 27) or sham stimulation (n = 26). The TBS treatment period was 22 days. Blood samples from 31 study subjects were obtained for analyses. The bilateral TBS group exhibited significantly greater decreases in depression scores than the sham group at week 4 (56.5% vs. 33.1%; p < 0.001 [effect size (Cohen ’ s d) = 1.00]) and during the 20-week follow-up periods. Significantly more responders were also found at week 4 (70.3% vs. 23.1%, p = 0.001) and during the 20-week follow-up periods. However, we did not detect any significant effects of TBS on the cytokine panels or any correlations between improvement in depressive symptoms and changes in serum inflammatory markers. Our findings provided the first evidence that the antidepressant efficacy of bilateral TBS monotherapy might not work via immune-modulating mechanisms.

Endocrine and immune effects of non-convulsive neurostimulation in depression: A systematic review

BACKGROUND

Non-convulsive neurostimulation is a rapidly-developing alternative to traditional treatment approaches in depression. Modalities such as repetitive Transcranial Magnetic Stimulation (rTMS), transcranial Direct Current Stimulation (tDCS), Vagal Nerve Stimulation (VNS) and Deep Brain Stimulation (DBS) are now recognized as potential treatments. How non-convulsive neurostimulation interventions impact the neurohormonal and neuroimmune changes that accompany depression remains relatively unknown. If this type of intervention can drive endocrine, immune, as well symptom changes in depression, non-convulsive neurostimulation may represent a viable, multi-faceted treatment approach in depression. We were therefore interested to understand the state of the literature in this developing area.

METHODS

A systematic review of all studies that examined the impact of non-convulsive neurostimulation interventions on the hypothalamic-pituitary-adrenal (HPA) axis and immune function in the form of cytokine production in depression.

RESULTS

We identified 15 human studies, 9 that examined rTMS, 2 that examined tDCS, 2 that examined VNS and 2 that examined electroacupuncture. 11 animal studies were also identified, 3 that examined rTMS, 2 that examined DBS and 6 that examined electroacupuncture. All types of non-convulsive neurostimulation were able to revert the increases in cortisol, ACTH and other components of the HPA axis that are seen in depressed patients, as well as to modulate the levels of key cytokines known to be up-regulated in depression, such as IL-1β, IL-6 and TNF-α. Changes in the HPA axis and levels of cytokines in response to non-convulsive neurostimulation often did not correlate with change in depressive symptoms. Most studies were not controlled trials and thus, significant methodologic variability existed. Furthermore, many human studies lacked a sham stimulation comparator arm. We were unable to conduct relevant meta-analyses due to the design heterogeneities, heterogeneity in the reported outcome measures and the limited number of studies retrieved. Animal studies generally supported the findings of those in human, but again, significant variability in methodology and study design were evident.

CONCLUSIONS

Non-convulsive neurostimulation interventions show promise in their ability to alter the endocrine and immune disturbances that accompany depression. Further research, which includes blinded, sham-controlled comparator designs is required.

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.

Fear and stressing in predator-prey ecology: considering the twin stressors of predators and people on mammals

Predators induce stress in prey and can have beneficial effects in ecosystems, but can also have negative effects on biodiversity if they are overabundant or have been introduced. The growth of human populations is, at the same time, causing degradation of natural habitats and increasing interaction rates of humans with wildlife, such that conservation management routinely considers the effects of human disturbance as tantamount to or surpassing those of predators. The need to simultaneously manage both of these threats is particularly acute in urban areas that are, increasingly, being recognized as global hotspots of wildlife activity. Pressures from altered predator-prey interactions and human activity may each initiate fear responses in prey species above those that are triggered by natural stressors in ecosystems. If fear responses are experienced by prey at elevated levels, on top of responses to multiple environmental stressors, chronic stress impacts may occur. Despite common knowledge of the negative effects of stress, however, it is rare that stress management is considered in conservation, except in intensive ex situ situations such as in captive breeding facilities or zoos. We propose that mitigation of stress impacts on wildlife is crucial for preserving biodiversity, especially as the value of habitats within urban areas increases. As such, we highlight the need for future studies to consider fear and stress in predator-prey ecology to preserve both biodiversity and ecosystem functioning, especially in areas where human disturbance occurs. We suggest, in particular, that non-invasive in situ investigations of endocrinology and ethology be partnered in conservation planning with surveys of habitat resources to incorporate and reduce the effects of fear and stress on wildlife.

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.

Repetitive magnetic stimulation protects corneal epithelium in a rabbit model of short-term exposure keratopathy

PURPOSE

To investigate the effect of repetitive magnetic stimulation (RMS) on corneal epithelial permeability in a rabbit model of exposure keratopathy.

METHODS

61 female New Zealand White (NZW) rabbits were treated on one eye with repetitive magnetic stimulation (RMS) at a frequency of 20 Hz for 15 min. The other eye was untreated. Rabbit eyes were kept open for 2 h to induce acute corneal desiccation. The extent of fluorescein corneal staining was evaluated using EpiView software and the concentration of fluorescein in the anterior chamber was determined by a fluorometer. Safety was evaluated by electroretinogram, spectral domain optical coherence tomography (SD-OCT) and histopathology. Expression pattern of corneal cell markers was determined by immunofluorescence.

RESULTS

A significant decrease in fluorescein concentration in the anterior chamber (54 ± 8.4 ng/ml vs. 146.5 ± 18.6 ng/ml, p = 0.000001) and in corneal surface fluorescein staining score (1.7 ± 0.2 vs. 4.6 ± 0.6, p = 0.00001) was obtained in RMS-treated eyes compared with control eyes, respectively. RMS treatment reduced by nearly 4 fold the percentage of corneal area with epithelial erosions by anterior segment SD-OCT. The therapeutic effect was maintained for at least 3 months. Increased expression of epithelial tight junction protein Zo-1 was observed in treated eyes. SD-OCT and histopathology analysis revealed no pathological changes in the treated or non-treated eyes.

CONCLUSIONS

RMS treatment decreases epithelial corneal erosions in a rabbit model of exposure keratopathy, with no indication of pathological changes. RMS may present a novel treatment for protection of corneal epithelium from desiccation.

UPLC-QTOF/MS-based metabolomics reveals the mechanism of chronic unpredictable mild stress-induced hypertension in rats

Hypertension is a common chronic disease, and it is the strongest risk factor for cardiovascular disease. Recently, the number of patients with hypertension-related complications has increased significantly, adding a heavy burden to the public health system. It is known that chronic stress plays an important role in the pathogenesis of cardiovascular diseases such as hypertension and stroke. However, the impact of hypertension on the dysfunctions induced by chronic stress remains poorly understood. In this study, using LC-MS-based metabolomics, we established a chronic stress model to demonstrate the mechanisms of stress-induced hypertension. We found that 30 metabolites in chronically stressed rats were changed; of these metabolites, seven had been upregulated, and 23 had been downregulated, including amino acids, phospholipids, carnitines and fatty acids, many of which are involved in amino acid metabolism, cell membrane injury, ATP supply and inflammation. These metabolites are engaged in dysregulated pathways and will provide a targeted approach to study the mechanism of stress-induced hypertension.

High frequency repetitive transcranial magnetic stimulation improves neuronal activity without affecting astrocytes and microglia density

Repetitive transcranial magnetic stimulation (rTMS) is a non-invasive neuromodulation technique capable of producing changes in the electrical potential of neurons. Currently, the application of rTMS in clinical practice and as a neurophysiological tool is increasing. However, the exact cellular mechanisms underlying rTMS-based therapies are not completely clear. Additionally, glial cells have been studied less. Our aim was to investigate the effect of three days of high-frequency rTMS on neuronal metabolism and neuronal activation, in addition to its effect on glial cells. For this purpose, we performed histochemistry and immunohistochemistry procedures: the histochemistry of cytochrome oxidase (COx) to assess neuronal metabolic activity, and the immunohistochemistry of c-Fos (marker of neuronal activity), GFAP (marker of astrocytic reactivity), and Iba1 (selective marker of reactive microglia). Our results showed enhanced metabolic activity after rTMS in the retrosplenial and parietal cortex and CA1 and CA3 subfields of the hippocampus. Moreover, higher c-Fos activity was found in the agranular retrosplenial cortex. Finally, we did not find changes between groups in the induction of astrocyte and microglia reactivity in any of the immunostained regions. In conclusion, we can assume that three days of high-frequency rTMS applied in healthy rats does not alter astroglia reactivity or inflammatory responses, such as microglia proliferation. Because we have shown an upregulation of neuronal metabolic activity in many limbic brain structures, in addition to higher c-Fos levels in the nearest cortical area to the rTMS, our work provides novel insight into the effectiveness and safety of rTMS as a brain modulation therapy.

rTMS ameliorated depressive-like behaviors by restoring HPA axis balance and prohibiting hippocampal neuron apoptosis in a rat model of depression

Repetitive transcranial magnetic stimulation (rTMS) has been widely used to treat depression. The mechanistic basis for the effects of rTMS is not well understood, although previous studies have suggested that it involves the regulation of hypothalamic-pituitary-adrenocortical (HPA) axis and protection of hippocampal neurons. We investigated this in the present study using a chronic unpredictable mild stress (CUMS) paradigm in Sprague-Dawley rats. The rats were subjected to rTMS for 15 consecutive days, and body weight, sucrose consumption, and locomotor activity were evaluated. B cell lymphoma-2-associated X protein (Bax) expression was assessed by immunohistochemistry; cell morphology was examined by Nissl staining; and adrenocorticotropic hormone (ACTH) and cortisol (CORT) levels in the hippocampus were measured by enzyme-linked immunosorbent assay. CUMS decreased body weight and sucrose consumption in rats along with horizontal/vertical distance traveled in the open field test. Rats subjected to CUMS also showed increased levels of Bax as well as ACTH and CORT; the hippocampal neurons in these animals had abnormal morphology and were reduced in number. rTMS reversed these changes and improved depression-like behaviors. Thus, rTMS abrogates the loss of hippocampal neurons and restores the balance of the HPA axis in the treatment of depression.

Noninvasive Brain Stimulation to Enhance Functional Recovery After Stroke: Studies in Animal Models

Background. Stroke is the leading cause of adult disability, but treatment options remain limited, leaving most patients with incomplete recovery. Patient and animal studies have shown potential of noninvasive brain stimulation (NIBS) strategies to improve function after stroke. However, mechanisms underlying therapeutic effects of NIBS are unclear and there is no consensus on which NIBS protocols are most effective. Objective. Provide a review of articles that assessed effects and mechanisms of repetitive transcranial magnetic stimulation (rTMS) and transcranial direct current stimulation (tDCS) in animal stroke models. Methods. Articles were searched in PubMed, including cross-references. Results. Nineteen eligible studies reporting effects of rTMS or tDCS after stroke in small rodents were identified. Seventeen of those described improved functional recovery or neuroprotection compared with untreated control or sham-stimulated groups. The effects of rTMS could be related to molecular mechanisms associated with ischemic tolerance, neuroprotection, anti-apoptosis, neurogenesis, angiogenesis, or neuroplasticity. Favorable outcome appeared most effectively when using high-frequency (>5 Hz) rTMS or intermittent theta burst stimulation of the ipsilesional hemisphere. tDCS effects were strongly dependent on stimulation polarity and onset time. Although these findings are promising, most studies did not meet Good Laboratory Practice assessment criteria. Conclusions. Despite limited data availability, animal stroke model studies demonstrate potential of NIBS to promote stroke recovery through different working mechanisms. Future studies in animal stroke models should adhere to Good Laboratory Practice guidelines and aim to further develop clinically applicable treatment protocols by identifying most favorable stimulation parameters, treatment onset, adjuvant therapies, and underlying modes of action.

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.

Differential effects of acute versus chronic stress on ethanol sensitivity: Evidence for interactions on both behavioral and neuroimmune outcomes

Acute alcohol intoxication induces significant alterations in brain cytokines. Since stress challenges also profoundly impact central cytokine expression, these experiments examined the influence of acute and chronic stress on ethanol-induced brain cytokine responses. In Experiment 1, adult male rats were exposed to acute footshock. After a post-stress recovery interval of 0, 2, 4, or 24 h, rats were administered ethanol (4 g/kg; intragastric), with trunk blood and brains collected 3 h later. In non-stressed controls, acute ethanol increased expression of Il-6 and IκBα in the hippocampus. In contrast, rats exposed to footshock 24 h prior to ethanol demonstrated potentiation of hippocampal Il-6 and IκBα expression relative to ethanol-exposed non-stressed controls. Experiment 2 subsequently examined the effects of chronic stress on ethanol-related cytokine expression. Following a novel chronic escalating stress procedure, rats were intubated with ethanol. As expected, acute ethanol increased Il-6 expression in all structures examined, yet the Il-6 response was attenuated exclusively in the hippocampus in chronically stressed rats. Later experiments determined that neither acute nor chronic stress affected ethanol pharmacokinetics. When ethanol hypnosis was examined, however, rats exposed to chronic stress awoke at significantly lower blood ethanol levels compared to acutely stressed rats, despite similar durations of ethanol-induced sedation. These data indicate that chronic stress may increase sensitivity to ethanol hypnosis. Together, these experiments demonstrate an intriguing interaction between recent stress history and ethanol-induced increases in hippocampal Il-6, and may provide insight into novel pharmacotherapeutic targets for prevention and treatment of alcohol-related health outcomes based on stress susceptibility.

Electromagnetic Fields for the Regulation of Neural Stem Cells

Localized magnetic fields (MFs) could easily penetrate the scalp, skull, and meninges, thus inducing an electrical current in both the central and peripheral nervous systems, which is primarily used in transcranial magnetic stimulation (TMS) for inducing specific effects on different regions or cells that play roles in various brain activities. Studies of repetitive transcranial magnetic stimulation (rTMS) have led to novel attractive therapeutic approaches. Neural stem cells (NSCs) in adult human brain are able to self-renew and possess multidifferential ability to maintain homeostasis and repair damage after acute central nervous system. In the present review, we summarized the electrical activity of NSCs and the fundamental mechanism of electromagnetic fields and their effects on regulating NSC proliferation, differentiation, migration, and maturation. Although it was authorized for the rTMS use in resistant depression patients by US FDA, there are still unveiling mechanism and limitations for rTMS in clinical applications of acute central nervous system injury, especially on NSC regulation as a rehabilitation strategy. More in-depth studies should be performed to provide detailed parameters and mechanisms of rTMS in further studies, making it a powerful tool to treat people who are surviving with acute central nervous system injuries.

Repetitive Transcranial Magnetic Stimulation Ameliorates Cognitive Impairment by Enhancing Neurogenesis and Suppressing Apoptosis in the Hippocampus in Rats with Ischemic Stroke

Cognitive impairment is a serious mental deficit caused by stroke that can severely affect the quality of a survivor's life. Repetitive transcranial magnetic stimulation (rTMS) is a well-known rehabilitation modality that has been reported to exert neuroprotective effects after cerebral ischemic injury. In the present study, we evaluated the therapeutic efficacy of rTMS against post-stroke cognitive impairment (PSCI) and investigated the mechanisms underlying its effects in a middle cerebral artery occlusion (MCAO) rat model. The results showed that rTMS ameliorated cognitive deficits and tended to reduce the sizes of cerebral lesions. In addition, rTMS significantly improved cognitive function via a mechanism involving increased neurogenesis and decreased apoptosis in the ipsilateral hippocampus. Moreover, brain-derived neurotrophic factor (BDNF) and its receptor, tropomyosin-related kinase B (TrkB), were clearly upregulated in ischemic hippocampi after treatment with rTMS. Additionally, further studies demonstrated that rTMS markedly enhanced the expression of the apoptosis-related B cell lymphoma/leukemia gene 2 (Bcl-2) and decreased the expression of the Bcl-2-associated protein X (Bax) and the number of TUNEL-positive cells in the ischemic hippocampus. Both protein levels and mRNA levels were investigated. Our findings suggest that after ischemic stroke, treatment with rTMS promoted the functional recovery of cognitive impairments by inhibiting apoptosis and enhancing neurogenesis in the hippocampus and that this mechanism might be mediated by the BDNF signaling pathway.

Notch1 deficiency in postnatal neural progenitor cells in the dentate gyrus leads to emotional and cognitive impairment

It is well known that Notch1 signaling plays a crucial role in embryonic neural development and adult neurogenesis. The latest evidence shows that Notch1 also plays a critical role in synaptic plasticity in mature hippocampal neurons. So far, deeper insights into the function of Notch1 signaling during the different steps of adult neurogenesis are still lacking, and the mechanisms by which Notch1 dysfunction is associated with brain disorders are also poorly understood. In the current study, we found that Notch1 was highly expressed in the adult-born immature neurons in the hippocampal dentate gyrus. Using a genetic approach to selectively ablate Notch1 signaling in late immature precursors in the postnatal hippocampus by cross-breeding doublecortin (DCX)⁺ neuron-specific proopiomelanocortin (POMC)-α Cre mice with floxed Notch1 mice, we demonstrated a previously unreported pivotal role of Notch1 signaling in survival and function of adult newborn neurons in the dentate gyrus. Moreover, behavioral and functional studies demonstrated that POMC-Notch1^-/- mutant mice showed anxiety and depressive-like behavior with impaired synaptic transmission properties in the dentate gyrus. Finally, our mechanistic study showed significantly compromised phosphorylation of cAMP response element-binding protein (CREB) in Notch1 mutants, suggesting that the dysfunction of Notch1 mutants is associated with the disrupted pCREB signaling in postnatally generated immature neurons in the dentate gyrus.-Feng, S., Shi, T., Qiu, J., Yang, H., Wu, Y., Zhou, W., Wang, W., Wu, H. Notch1 deficiency in postnatal neural progenitor cells in the dentate gyrus leads to emotional and cognitive impairment.

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.

Biochemical effects of venlafaxine on astrocytes as revealed by 1H NMR-based metabolic profiling

As a serotonin–norepinephrine reuptake inhibitor [SNRI], venlafaxine is one of the most commonly prescribed clinical antidepressants, with a broad range of antidepressant effects.

Repetitive Transcranial Magnetic Stimulation of the Brain: Mechanisms from Animal and Experimental Models

Since the development of transcranial magnetic stimulation (TMS) in the early 1980s, a range of repetitive TMS (rTMS) protocols are now available to modulate neuronal plasticity in clinical and non-clinical populations. However, despite the wide application of rTMS in humans, the mechanisms underlying rTMS-induced plasticity remain uncertain. Animal and in vitro models provide an adjunct method of investigating potential synaptic and non-synaptic mechanisms of rTMS-induced plasticity. This review summarizes in vitro experimental studies, in vivo studies with intact rodents, and preclinical models of selected neurological disorders-Parkinson's disease, depression, and stroke. We suggest that these basic research findings can contribute to the understanding of how rTMS-induced plasticity can be modulated, including novel mechanisms such as neuroprotection and neurogenesis that have significant therapeutic potential.