Neuroprotective effects of subthalamic nucleus high-frequency stimulation on substantia nigra neurons in a Parkinson's disease rat model

BACKGROUND： Deep-brain stimulation has proven to be beneficial in the treatment of Parkinson＇s disease （PD） patients. OBJECTIVE： To investigate the effects of high-frequency stimulation （HFS） to the subthalamic nucleus （STN） on neuronal apoptosis and apoptosis-related gene expression in the substantia nigra pars compacta, and to analyze the neuroprotective effect of HFS-STN. DESIGN, TIME AND SETTING： Neuronal morphology experiments were performed in the Beijing Neurosurgical Institute from May to December in 2005. MATERIALS： Forty healthy, adult, Sprague Dawley rats were used to establish a PD model with a unilateral microinjection of 6-hydroxydopamine into two target areas of the right medial forebrain bundle. 6-hydroxydopamine was purchased from Sigma （USA）; high-frequency electrical stimulator was produced by World Precision Instruments （USA）; Terminal deoxynucleotidyl transferase dUTP nick end labeling （TUNEL） kit was a product of Nanjing Jiancheng Technology Co., Ltd. （China）; and Bcl-2 and Bax protein assay kit were purchased from Wuhan Boster Bioengineering Co., Ltd. （China）. METHODS： Forty rats were randomly divided into three groups. The stimulation group （n = 15） received HFS-STN on the day of PD modeling. The PD model group （n = 15） was used to establish the PD model. The control group （n = 10） was injected with normal saline containing 0.2 g/L ascorbic acid into two areas of the right medial forebrain bundle. MAIN OUTCOME MEASURES： Survival of dopaminergic neurons in the substantia nigra pars compacta was determined using Nissl staining. Apoptosis of dopaminergic neurons was detected using TUNEL techniques. Expression of anti-apoptotic protein, Bcl-2, and pro-apoptotic protein, Bax, were assayed by immunohistochemistry. RESULTS： Following 6-hydroxydopamine injection, the number of substantia nigra pars compacta neurons was reduced in the stimulation and PD model groups, compared to the control group. At 2 and 4 weeks post-surgery, the grey value of Nissl stained images was significantly less in the PD model and stimulation groups （P 〈 0.05）, and the stimulation group exhibited greater grey values compared to the model group （P 〈 0.05）. At 2 and 4 weeks post-surgery, the number of apoptotic neurons was significantly less in the stimulation group compared to the model group （P 〈 0.05）. In addition, Bcl-2 and Bax expression, as well as the Bcl-2/Bax ratio, was much higher in the stimulation group compared to the model group （P 〈 0.05）. CONCLUSION： HFS-STN has a neuroprotective effect on dopaminergic neurons in the substantia nigra pars compacta of PD rats by promoting Bcl-2 expression, inhibiting Bax expression, and reducing the number of apoptotic dopaminergic neurons.

High-frequency Stimulation of Subthalamic Nucleus for Treatment of Parkinson's Disease

Degeneration and death of the neurons of the substantia nigra can cause a deficit in brain dopamine, leading to loss of movement control The subthalamic nucleus is a junction of basal ganglia neural circuit and can regulate the efferent information of basal ganglia and control motor activity. High-frequency stimulation of the subthalamic nucleus can alter dopamine levels as well as related factor expression in the corpus striatum and thereby improve the symptoms of Parkinson＇s disease.

Hippocampal High-Frequency Stimulation Inhibites the Progression of Rapid Kindling-Induced Seizure in Rats

Epilepsy is one of the most common serious neurological disorders. Pharmacoresistant epilepsy patients are poorly controlled or their seizures are refractory to drug treatment. Resective surgery is frequently a promising therapy in this population, however, not all the patients meet the eligibility criteria for the surgical treatment. Deep brain stimulation has been investigated in clinical studies and animal studies as an alternative treatment, but the optimal stimulation parameters remain an issue. The present study was designed to investigate the effect of unilateral high-frequency stimulation (HFS) of hippocampus on seizure development by using the hippocampal rapid kindling method (hRK) in rats, and compared the results with those of low-frequency stimulation previously published by our group. We used male Wistar rats implanted with electrodes in the ventral hippocampus. All rats underwent hRK (biphasic square wave pulses, 20 Hz for 10 seconds) during three consecutive days (twelve stimulations per day). The control group (hRK;n = 7) received only RK stimulus, while the treated group (HFS-hRK;n = 9) received also HFS (biphasic square wave pulses, 130 Hz for 30 seconds) immediately before the RK stimulus, during three consecutive days. At the end of behavioral testing 78% (p 0.01) of the animals receiving HFS treatment were still not fully kindled staying in stages 0 -III (p 0.01). HFS group needed a higher number of stimulations to achieve stage III (p 0.05) with respect to control group. However, no significant differences in the cumulative daily afterdischarge duration were observed. HFS did not present significant differences compared with LFS in any of studied parameters. The findings suggest that unilateral HFS applied on hippocampus effectively inhibited the epileptogenic process induced by hippocampal rapid kindling. According to the comparative results about hippocampal rapid kindled animals stimulated with HFS and LFS (5 Hz), we found no conclusive information on which treatment is most efficient.

Involvement of GABAergic pathway on inhibition of subthalamic nucleus high-frequency stimulation of spontaneous firing activity in substantia nigra pars reticulata neurons in a rat model of Parkinson's disease

BACKGROUND： Subthalamic nucleus-high frequency stimulation （STN-HFS） plays an important role in the treatment of Parkinson＇s disease, but the mechanisms underlying STN-HFS remain unclear. Some studies have demonstrated that STN stimulation inhibits the firing activity of substantia nigra pars reticulata neurons. OBJECTIVE： To investigate the effects of different-frequency STN stimulation and microiontophoresis of gamma-aminobutyric acid （GABA） and its antagonist, bicuculline, on spontaneous firing activity in a rat model of Parkinson＇s disease, and to analyze the action pathway of high frequency stimulation in firing activity inhibition of substantia nigra pars reticulata neurons. DESIGN, TIME AND SETTING： This neuroelectrophysiological, animal experiment was performed at the Electrophysiology Laboratory of Liaoning Medical University, China from March to August 2008. MATERIALS： 6-hydroxydopamine （6-OHDA） （Sigma, USA）, A320R isolated stimulus and DAM80 preamplifier （World Precision Instruments, USA）, 6400A microiontophoresis apparatus （Dagan, USA）, and Spike 2 biological signal acquisition system （CED, UK） were used in this study. METHODS： A total of 20 Sprague Dawley rats were used to establish a Parkinson＇s disease model via injection of 6-OHDA into the right striatum. Electrical stimulation （0.06-ms width, 0.4-mA intensity 20-200-Hz frequency, 5-second train duration） was delivered to the subthalamic nucleus. Peripheral channels were separately filled with GABA （pH 3.5, 0.2 mol/L）, bicuculline （pH 4.0, 0.01 mol/L）, and NaCI （pH 7.0, 3 mol/L）. The electrode was positioned with a WK-2 microelectrode propulsion device, and was slowly inserted into the substantia nigra pars reticulata to record spontaneous firing activity of substantia nigra pars reticulata neurons. MAIN OUTCOME MEASURES： The number and firing rate of substantia nigra pars reticulata neurons which were either inhibited or excited were measured. RESULTS： Substantia nigra pars reticulata neurons were inhibited by STN stimulation. The proportion of inhibited substantia nigra pars reticulata neurons increased with increasing stimulation frequency. GABA had a tonic inhibitory effect on substantia nigra pars reticulata neurons. Microiontophoresis of bicuculline suppressed the inhibitory effect of STN-HFS on 67% （4/6） of substantia nigra pars reticulata neurons. CONCLUSION： STN-HFS ameliorated abnormal activity in substantia nigra pars reticulata neurons via the inhibitory effect of GABA treatment in a rat model of Parkinson＇s disease.

High-frequency repetitive transcranial magnetic stimulation promotes neural stem cell proliferation after ischemic stroke

Prolife ration of neural stem cells is crucial for promoting neuronal regeneration and repairing cerebral infarction damage.Transcranial magnetic stimulation(TMS)has recently emerged as a tool for inducing endogenous neural stem cell regeneration,but its underlying mechanisms remain unclea r In this study,we found that repetitive TMS effectively promotes the proliferation of oxygen-glucose deprived neural stem cells.Additionally,repetitive TMS reduced the volume of cerebral infa rction in a rat model of ischemic stro ke caused by middle cerebral artery occlusion,im p roved rat cognitive function,and promoted the proliferation of neural stem cells in the ischemic penumbra.RNA-sequencing found that repetitive TMS activated the Wnt signaling pathway in the ischemic penumbra of rats with cerebral ischemia.Furthermore,PCR analysis revealed that repetitive TMS promoted AKT phosphorylation,leading to an increase in mRNA levels of cell cycle-related proteins such as Cdk2 and Cdk4.This effect was also associated with activation of the glycogen synthase kinase 3β/β-catenin signaling pathway,which ultimately promotes the prolife ration of neural stem cells.Subsequently,we validated the effect of repetitive TMS on AKT phosphorylation.We found that repetitive TMS promoted Ca2+influx into neural stem cells by activating the P2 calcium channel/calmodulin pathway,thereby promoting AKT phosphorylation and activating the glycogen synthase kinase 3β/β-catenin pathway.These findings indicate that repetitive TMS can promote the proliferation of endogenous neural stem cells through a Ca2+influx-dependent phosphorylated AKT/glycogen synthase kinase 3β/β-catenin signaling pathway.This study has produced pioneering res ults on the intrinsic mechanism of repetitive TMS to promote neural function recove ry after ischemic stro ke.These results provide a stro ng scientific foundation for the clinical application of repetitive TMS.Moreover,repetitive TMS treatment may not only be an efficient and potential approach to support neurogenesis for further therapeutic applications,but also provide an effective platform for the expansion of neural stem cells.

High-frequency stimulation of anterior nucleus thalamus improves impaired cognitive function induced by intra-hippocampal injection of Aβ1-40 in rats

Background The advent of brain stimulation techniques to treat movement disorders and psychiatric diseases has shown potential to decode the neural mechanism that underlies the cognitive process by modulating the interrupted circuit.Here,the present investigation aimed at evaluating the influence of deep brain stimulation of the anterior nucleus thalamus （ANT-DBS） on memory.Methods Thirty-two rats were randomized into phosphate buffer saline （PBS） group （n=8,rats received PBS injections without implantation of electrodes into the ANT）,Alzheimer＇s dementia （AD） group （n=8,rats received Aβ1-40 injections without implantation of electrodes into the ANT）,ANT sham stimulation group （n=8,rats received Aβ1-40 injections with implantation of electrodes into the ANT but without stimulation） and ANT stimulation group （n=8,rats received Aβ1-40 injections with implantation of electrodes into the ANT and stimulation）.A Morris maze test was used for determining the effect of electrical stimulation on cognitive function in rats.The data were assessed statistically with one-way analysis of variance （ANOVA） followed by Tukey＇s tests for multiple post hoc comparisons.Results The data showed that in the training test,PBS group and AD group managed to learn the hidden-platform faster and faster while AD group needed a significantly longer time to reach the platform than PBS group （P ＜0.05）.Meanwhile,ANT stimulation group demonstrated a significantly shorter time to reach the platform （P ＜0.05） compared to the AD group,while there was no significant difference between the ANT sham stimulation group and the AD group （P ＞0.05）.On the probe test,the AD group spent less time （（10.15±2.34） seconds） in the target quadrant than the PBS group （（28.20±2.75） seconds） （P ＜0.05）.And the times of platform-traversing of the AD group （3.35±1.12） significantly decreased compared with the PBS group （8.69±2.87） （P ＜0.05）.However,the times of platform-traversing and the time spent in the target quadrant of the ANT stimulation group significantly increased compared to the AD group （P ＜0.05）,while times of platformtraversing or the time spent in the target quadrant was not significantly different between the ANT sham stimulation group and the AD group （P ＞0.05）.Conclusion Bilateral high-frequency stimulation of the ANT may be useful as a potential therapeutic modality for cognitive dysfunction in AD.

Treadmill exercise in combination with acousto-optic and olfactory stimulation improves cognitive function in APP/PS1 mice through the brain-derived neurotrophic factor-and Cygb-associated signaling pathways

A reduction in adult neurogenesis is associated with behavioral abnormalities in patients with Alzheimer's disease.Consequently,enhancing adult neurogenesis represents a promising therapeutic approach for mitigating disease symptoms and progression.Nonetheless,nonpharmacological interventions aimed at inducing adult neurogenesis are currently limited.Although individual non-pharmacological interventions,such as aerobic exercise,acousto-optic stimulation,and olfactory stimulation,have shown limited capacity to improve neurogenesis and cognitive function in patients with Alzheimer's disease,the therapeutic effect of a strategy that combines these interventions has not been fully explored.In this study,we observed an age-dependent decrease in adult neurogenesis and a concurrent increase in amyloid-beta accumulation in the hippocampus of amyloid precursor protein/presenilin 1 mice aged 2-8 months.Amyloid deposition became evident at 4 months,while neurogenesis declined by 6 months,further deteriorating as the disease progressed.However,following a 4-week multifactor stimulation protocol,which encompassed treadmill running(46 min/d,10 m/min,6 days per week),40 Hz acousto-optic stimulation(1 hour/day,6 days/week),and olfactory stimulation(1 hour/day,6 days/week),we found a significant increase in the number of newborn cells(5'-bromo-2'-deoxyuridine-positive cells),immature neurons(doublecortin-positive cells),newborn immature neurons(5'-bromo-2'-deoxyuridine-positive/doublecortin-positive cells),and newborn astrocytes(5'-bromo-2'-deoxyuridine-positive/glial fibrillary acidic protein-positive cells).Additionally,the amyloid-beta load in the hippocampus decreased.These findings suggest that multifactor stimulation can enhance adult hippocampal neurogenesis and mitigate amyloid-beta neuropathology in amyloid precursor protein/presenilin 1 mice.Furthermore,cognitive abilities were improved,and depressive symptoms were alleviated in amyloid precursor protein/presenilin 1 mice following multifactor stimulation,as evidenced by Morris water maze,novel object recognition,forced swimming test,and tail suspension test results.Notably,the efficacy of multifactor stimulation in consolidating immature neurons persisted for at least 2weeks after treatment cessation.At the molecular level,multifactor stimulation upregulated the expression of neuron-related proteins(NeuN,doublecortin,postsynaptic density protein-95,and synaptophysin),anti-apoptosis-related proteins(Bcl-2 and PARP),and an autophagyassociated protein(LC3B),while decreasing the expression of apoptosis-related proteins(BAX and caspase-9),in the hippocampus of amyloid precursor protein/presenilin 1 mice.These observations might be attributable to both the brain-derived neurotrophic factor-mediated signaling pathway and antioxidant pathways.Furthermore,serum metabolomics analysis indicated that multifactor stimulation regulated differentially expressed metabolites associated with cell apoptosis,oxidative damage,and cognition.Collectively,these findings suggest that multifactor stimulation is a novel non-invasive approach for the prevention and treatment of Alzheimer's disease.

Prolonged intermittent theta burst stimulation restores the balance between A_(2A)R-and A_(1)R-mediated adenosine signaling in the 6-hydroxidopamine model of Parkinson's disease

An imbalance in adenosine-mediated signaling,particularly the increased A_(2A)R-mediated signaling,plays a role in the pathogenesis of Parkinson's disease.Existing therapeutic approaches fail to alter disease progression,demonstrating the need for novel approaches in PD.Repetitive transcranial magnetic stimulation is a non-invasive approach that has been shown to improve motor and non-motor symptoms of Parkinson's disease.However,the underlying mechanisms of the beneficial effects of repetitive transcranial magnetic stimulation remain unknown.The purpose of this study is to investigate the extent to which the beneficial effects of prolonged intermittent theta burst stimulation in the 6-hydroxydopamine model of experimental parkinsonism are based on modulation of adenosine-mediated signaling.Animals with unilateral 6-hydroxydopamine lesions underwent intermittent theta burst stimulation for 3 weeks and were tested for motor skills using the Rotarod test.Immunoblot,quantitative reverse transcription polymerase chain reaction,immunohistochemistry,and biochemical analysis of components of adenosine-mediated signaling were performed on the synaptosomal fraction of the lesioned caudate putamen.Prolonged intermittent theta burst stimulation improved motor symptoms in 6-hydroxydopamine-lesioned animals.A 6-hydroxydopamine lesion resulted in progressive loss of dopaminergic neurons in the caudate putamen.Treatment with intermittent theta burst stimulation began 7 days after the lesion,coinciding with the onset of motor symptoms.After treatment with prolonged intermittent theta burst stimulation,complete motor recovery was observed.This improvement was accompanied by downregulation of the e N/CD73-A_(2A)R pathway and a return to physiological levels of A_(1)R-adenosine deaminase 1 after 3 weeks of intermittent theta burst stimulation.Our results demonstrated that 6-hydroxydopamine-induced degeneration reduced the expression of A_(1)R and elevated the expression of A_(2A)R.Intermittent theta burst stimulation reversed these effects by restoring the abundances of A_(1)R and A_(2A)R to control levels.The shift in ARs expression likely restored the balance between dopamine-adenosine signaling,ultimately leading to the recovery of motor control.

Repetitive transcranial magnetic stimulation in Alzheimer’s disease:effects on neural and synaptic rehabilitation

Alzheimer’s disease is a neurodegenerative disease resulting from deficits in synaptic transmission and homeostasis.The Alzheimer’s disease brain tends to be hyperexcitable and hypersynchronized,thereby causing neurodegeneration and ultimately disrupting the operational abilities in daily life,leaving patients incapacitated.Repetitive transcranial magnetic stimulation is a cost-effective,neuro-modulatory technique used for multiple neurological conditions.Over the past two decades,it has been widely used to predict cognitive decline;identify pathophysiological markers;promote neuroplasticity;and assess brain excitability,plasticity,and connectivity.It has also been applied to patients with dementia,because it can yield facilitatory effects on cognition and promote brain recovery after a neurological insult.However,its therapeutic effectiveness at the molecular and synaptic levels has not been elucidated because of a limited number of studies.This study aimed to characterize the neurobiological changes following repetitive transcranial magnetic stimulation treatment,evaluate its effects on synaptic plasticity,and identify the associated mechanisms.This review essentially focuses on changes in the pathology,amyloidogenesis,and clearance pathways,given that amyloid deposition is a major hypothesis in the pathogenesis of Alzheimer’s disease.Apoptotic mechanisms associated with repetitive transcranial magnetic stimulation procedures and different pathways mediating gene transcription,which are closely related to the neural regeneration process,are also highlighted.Finally,we discuss the outcomes of animal studies in which neuroplasticity is modulated and assessed at the structural and functional levels by using repetitive transcranial magnetic stimulation,with the aim to highlight future directions for better clinical translations.

High-frequency spinal cord stimulation produces longlasting analgesic effects by restoring lysosomal function and autophagic flux in the spinal dorsal horn

High-frequency spinal cord stimulation(HF-SCS) has been established as an effective therapy for neuropathic pain. However, the analgesic mechanisms involved in HF-SCS remain to be clarified. In our study, adult rat neuropathic pain was induced by spinal nerve ligation. Two days after modeling, the rats were subjected to 4 hours of HF-SCS(motor threshold 50%, frequency 10,000 Hz, and pulse width 0.024 ms) in the dorsal horn of the spinal cord. The results revealed that the tactile allodynia of spinal nerve-injured rats was markedly alleviated by HFSCS, and the effects were sustained for 3 hours after the stimulation had ceased. HF-SCS restored lysosomal function, increased the levels of lysosome-associated membrane protein 2(LAMP2) and the mature form of cathepsin D(matu-CTSD), and alleviated the abnormally elevated levels of microtubule-associated protein 1 A/B-light chain 3(LC3)-II and sequestosome 1(P62) in spinal nerve-injured rats. HF-SCS also mostly restored the immunoreactivity of LAMP2, which was localized in neurons in the superficial layers of the spinal dorsal horn in spinal nerve-injured rats. In addition, intraperitoneal administration of 15 mg/kg chloroquine for 60 minutes reversed the expression of the aforementioned proteins and shortened the timing of the analgesic effects of HF-SCS. These findings suggest that HF-SCS may exhibit longlasting analgesic effects on neuropathic pain in rats through improving lysosomal dysfunction and alleviating autophagic flux. This study was approved by the Laboratory Animal Ethics Committee of China Medical University, Shenyang, China(approval No. 2017 PS196 K) on March 1, 2017.

Delayed improvements in visual memory task performance among chronic schizophrenia patients after high-frequency repetitive transcranial magnetic stimulation

BACKGROUND Cognitive impairments are core characteristics of schizophrenia,but are largely resistant to current treatments.Several recent studies have shown that highfrequency repetitive transcranial magnetic stimulation(rTMS)of the left dorsolateral prefrontal cortex(DLPFC)can reduce negative symptoms and improve certain cognitive deficits in schizophrenia patients.However,results are inconsistent across studies.AIM To examine if high-frequency rTMS of the DLPFC can improve visual memory deficits in patients with schizophrenia.METHODS Forty-seven chronic schizophrenia patients with severe negative symptoms on stable treatment regimens were randomly assigned to receive active rTMS to the DLPFC(n=25)or sham stimulation(n=22)on weekdays for four consecutive weeks.Patients performed the pattern recognition memory(PRM)task from the Cambridge Neuropsychological Test Automated Battery at baseline,at the end of rTMS treatment(week 4),and 4 wk after rTMS treatment(week 8).Clinical symptoms were also measured at these same time points using the Scale for the Assessment of Negative Symptoms(SANS)and the Positive and Negative Syndrome Scale(PANSS).RESULTS There were no significant differences in PRM performance metrics,SANS total score,SANS subscores,PANSS total score,and PANSS subscores between active and sham rTMS groups at the end of the 4-wk treatment period,but PRM performance metrics(percent correct and number correct)and changes in these metrics from baseline were significantly greater in the active rTMS group at week 8 compared to the sham group(all P<0.05).Active rTMS treatment also significantly reduced SANS score at week 8 compared to sham treatment.Moreover,the improvement in visual memory was correlated with the reduction in negative symptoms at week 8.In contrast,there were no between-group differences in PANSS total score and subscale scores at either week 4 or week 8(all P>0.05).CONCLUSION High-frequency transcranial magnetic stimulation improves visual memory and reduces negative symptoms in schizophrenia,but these effects are delayed,potentially due to the requirement for extensive neuroplastic changes within DLPFC networks.

Effect of the combination of high-frequency repetitive magnetic stimulation and neurotropin on injured sciatic nerve regeneration in rats

Repetitive magnetic stimulation is effective for treating posttraumatic neuropathies following spinal or axonal injury.Neurotropin is a potential treatment for nerve injuries like demyelinating diseases.This study sought to observe the effects of high-frequency repetitive magnetic stimulation,neurotropin and their combined use in the treatment of peripheral nerve injury in 32 adult male Sprague-Dawley rats.To create a sciatic nerve injury model,a 10 mm-nerve segment of the left sciatic nerve was cut and rotated through 180°and each end restored continuously with interrupted sutures.The rats were randomly divided into four groups.The control group received only a reversed autograft in the left sciatic nerve with no treatment.In the high-frequency repetitive magnetic stimulation group,peripheral high-frequency repetitive magnetic stimulation treatment(20 Hz,20 min/d)was delivered for 10 consecutive days after auto-grafting.In the neurotropin group,neurotropin therapy(0.96 NU/kg per day)was administrated for 10 consecutive days after surgery.In the combined group,the combination of peripheral high-frequency repetitive magnetic stimulation(20 Hz,20 min/d)and neurotropin(0.96 NU/kg per day)was given for 10 consecutive days after the operation.The Basso-Beattie-Bresnahan locomotor rating scale was used to assess the behavioral recovery of the injured nerve.The sciatic functional index was used to evaluate the recovery of motor functions.Toluidine blue staining was performed to determine the number of myelinated fibers in the distal and proximal grafts.Immunohistochemistry staining was used to detect the length of axons marked by neurofilament 200.Our results reveal that the Basso-Beattie-Bresnahan locomotor rating scale scores,sciatic functional index,the number of myelinated fibers in distal and proximal grafts were higher and axon lengths were longer in the high-frequency repetitive magnetic stimulation,neurotropin and combined groups compared with the control group.These measures were not significantly different among the high-frequency repetitive magnetic stimulation,neurotropin and combined groups.Therefore,our results suggest that peripheral high-frequency repetitive magnetic stimulation or neurotropin can promote the repair of injured sciatic nerves,but their combined use seems to offer no significant advantage.This study was approved by the Animal Ethics Committee of the Affiliated Changzhou No.2 People’s Hospital of Nanjing Medical University,China on December 23,2014(approval No.2014keyan002-01).

High-frequency magnetic stimulation attenuates beta-amyloid protein 1-42 neurotoxicity in organotypic hippocampal slices

Repetitive transcranial magnetic stimulation （rTMS） has been utilized as a therapeutic tool for neurodegenerative disorders including Alzheimer＇s disease. However, the precise mechanisms of its clinical effects remain unknown. β-amyloid （Aβ） exhibits direct neurotoxic effects and is closely related to neuronal degeneration in Alzheimer＇s disease. Therefore, it has been hypothesized that the neuroprotective effects of rTMS are related to the mechanisms of protection against Aβ neurotoxicity. Organotypic hippocampal slices were prepared from 8-day old, Sprague Dawley rats. The tissue slices were exposed to 100 μmol/L Al3142 since day 12 in vitro with and without high-frequency （20 Hz） magnetic stimulation. Magnetic stimulation efficacy was evaluated by measuring neuronal nuclei （NeuN） protein expression and by observing cultures following propidium iodide fluorescence staining and bromodeoxyuridine （BrdU） immunohistochemistry. Lactate dehydrogenase activity was detected in the culture media to evaluate hippocampal neuronal damage. Our results demonstrated that high-frequency magnetic stimulation significantly reversed the reduction of NeuN protein expression because of Aβ1-42 exposure （P 〈 0.05） and significantly reduced the number of damaged cells in the hippocampal slices （P 〈 0.05）. However, lactate dehydrogenase levels and anti-BrdU staining results did not reveal any statistical differences These findings indicate that high-frequency magnetic stimulation might have protective effect on hippocampal neurons from Aβ1-42 neurotoxicity.

Neuroimaging mechanisms of high-frequency repetitive transcranial magnetic stimulation for treatment of amnestic mild cognitive impairment:a double-blind randomized sham-controlled trial

Individuals with amnestic mild cognitive impairment(aMCI)have a high risk of developing Alzheimer’s disease.Although repetitive transcranial magnetic stimulation(rTMS)is considered a potentially effective treatment for cognitive impairment in patients with aMCI,the neuroimaging mechanisms are poorly understood.Therefore,we performed a double-blind randomized sham-controlled trial in which rTMS was applied to the left dorsolateral prefrontal cortex of aMCI patients recruited from a community near the Third Hospital Affiliated to Sun Yat-sen University,China.Twenty-four patients with aMCI were randomly assigned to receive true rTMS(treatment group,n=12,6 men and 6 women;age 65.08±4.89 years)or sham stimulation(sham group,n=12,5 men and 7 women;age 64.67±4.77 years).rTMS parameters included a stimulation frequency of 10 Hz,stimulation duration of 2 seconds,stimulation interval of 8 seconds,20 repetitions at 80%of the motor threshold,and 400 pulses per session.rTMS/sham stimulation was performed five times per week over a period of 4 consecutive weeks.Our results showed that compared with baseline,Montreal Cognitive Assessment scores were significantly increased and the value of the amplitude of low-frequency fluctuation(ALFF)was significantly increased at the end of treatment and 1 month after treatment.Compared with the sham group,the ALFF values in the right inferior frontal gyrus,triangular part of the inferior frontal gyrus,right precuneus,left angular gyrus,and right supramarginal gyrus were significantly increased,and the ALFF values in the right superior frontal gyrus were significantly decreased in the treatment group.These findings suggest that high-frequency rTMS can effectively improve cognitive function in aMCI patients and alter spontaneous brain activity in cognitive-related brain areas.This study was approved by the Ethics Committee of Shenzhen Baoan Hospital of Southern Medical University,China(approval No.BYL20190901)on September 3,2019 and registered in the Chinese Clinical Trials Registry(registration No.ChiCTR1900028180)on December 14,2019.

Inhibition of the reinstatement of morphine-induced place preference in rats by high-frequency stimulation of the bilateral nucleus accumbens

Background Opiate addiction remains intractable in a large percentage of patients, and relapse is the biggest hurdle to recovery. Many studies have identified a central role of the nucleus accumbens （NAc） in addiction. Deep brain stimulation （DBS） has the advantages of being reversible, adjustable, and minimally invasive, and it has become a potential neurobiological intervention for addiction. The purpose of our study was to investigate whether high-frequency DBS in the NAc effectively attenuates the reinstatement of morphine seeking in morphine-primed rats. Methods A morphine-dependent group of rats was given increasing doses of morphine during conditioned place preference training. A control group of rats was given equal volumes of saline. After the establishment of this model, withdrawal syndromes were precipitated in these two groups by administering naloxone, and the differences in withdrawal symptoms between the groups were analyzed. Electrodes for DBS were implanted in the bilateral shell of the NAc in the experimental group. The rats were stimulated daily in the NAc for 5 hours per day over 30 days. Changes in the conditioned place preference test and withdrawal symptoms in the rats were investigated and place navigation studies were performed using the Morris water maze. The data were assessed statistically with one-way analysis of variance （ANOVA） followed by Tukey＇s tests for multiple post hoc comparisons. Results High-frequency stimulation of the bilateral NAc prevented the morphine-induced reinstatement of morphine seeking in the conditioned place preference test. The time spent in the white compartment by rats following 30 days of DBS （（268.25±25.07） seconds） was not significantly different compared with the time spent in the white compartment after relapse was induced by morphine administration （（303.29±34.22） seconds）. High-frequency stimulation of the bilateral NAc accelerated the innate decay of drug craving in morphine-dependent rats without significantly influencing learning and memory. Conclusion Bilateral high-frequency stimulation of the shell of the NAc may be useful as a novel therapeutic modality for the treatment of severe morphine addiction.

High-frequency and brief-pulse stimulation pulses terminate cortical electrical stimulation-induced afterdischarges

Brief-pulse stimulation at 50 Hz has been shown to terminate afterdischarges observed in epilepsy patients. However, the optimal pulse stimulation parameters for terminating cortical electrical stimulation-induced afterdischarges remain unclear. In the present study, we examined the effects of different brief-pulse stimulation frequencies（5, 50 and 100 Hz） on cortical electrical stimulation-induced afterdischarges in 10 patients with refractory epilepsy. Results demonstrated that brief-pulse stimulation could terminate cortical electrical stimulation-induced afterdischarges in refractory epilepsy patients. In conclusion,（1） a brief-pulse stimulation was more effective when the afterdischarge did not extend to the surrounding brain area.（2） A higher brief-pulse stimulation frequency（especially 100 Hz） was more likely to terminate an afterdischarge.（3） A low current intensity of brief-pulse stimulation was more likely to terminate an afterdischarge.

Contribution of glial cells to the neuroprotective effects triggered by repetitive magnetic stimulation:a systematic review

Repetitive transcranial magnetic stimulation has been increasingly studied in different neurological diseases,and although most studies focus on its effects on neuronal cells,the contribution of nonneuronal cells to the improvement trigge red by repetitive transcranial magnetic stimulation in these diseases has been increasingly suggested.To systematically review the effects of repetitive magnetic stimulation on non-neuronal cells two online databases.Web of Science and PubMed were searched fo r the effects of high-frequency-repetitive transcranial magnetic stimulation,low-frequencyrepetitive transcranial magnetic stimulation,intermittent theta-bu rst stimulation,continuous thetaburst stimulation,or repetitive magnetic stimulation on non-neuronal cells in models of disease and in unlesioned animals or cells.A total of 52 studies were included.The protocol more frequently used was high-frequency-repetitive magnetic stimulation,and in models of disease,most studies report that high-frequency-repetitive magnetic stimulation led to a decrease in astrocyte and mic roglial reactivity,a decrease in the release of pro-inflammatory cyto kines,and an increase of oligodendrocyte proliferation.The trend towards decreased microglial and astrocyte reactivity as well as increased oligodendrocyte proliferation occurred with intermittent theta-burst stimulation and continuous theta-burst stimulation.Few papers analyzed the low-frequency-repetitive transcranial magnetic stimulation protocol,and the parameters evaluated were restricted to the study of astrocyte reactivity and release of pro-inflammatory cytokines,repo rting the absence of effects on these paramete rs.In what concerns the use of magnetic stimulation in unlesioned animals or cells,most articles on all four types of stimulation reported a lack of effects.It is also important to point out that the studies were developed mostly in male rodents,not evaluating possible diffe rential effects of repetitive transcranial magnetic stimulation between sexes.This systematic review supports that thro ugh modulation of glial cells repetitive magnetic stimulation contributes to the neuroprotection or repair in various neurological disease models.Howeve r,it should be noted that there are still few articles focusing on the impact of repetitive magnetic stimulation on non-neuronal cells and most studies did not perform in-depth analyses of the effects,emphasizing the need for more studies in this field.

Vagus nerve stimulation in cerebral stroke:biological mechanisms,therapeutic modalities,clinical applications,and future directions

Stroke is a major disorder of the central nervous system that poses a serious threat to human life and quality of life.Many stro ke victims are left with long-term neurological dysfunction,which adversely affects the well-being of the individual and the broader socioeconomic impact.Currently,poststroke brain dysfunction is a major and difficult area of treatment.Vagus nerve stimulation is a Food and Drug Administration-approved exploratory treatment option for autis m,refractory depression,epilepsy,and Alzheimer’s disease.It is expected to be a novel therapeutic technique for the treatment of stroke owing to its association with multiple mechanisms such as alte ring neurotransmitters and the plasticity of central neuro ns.In animal models of acute ischemic stroke,vagus nerve stimulation has been shown to reduce infarct size,reduce post-stroke neurological damage,and improve learning and memory capacity in rats with stroke by reducing the inflammatory response,regulating bloodbrain barrier permeability,and promoting angiogenesis and neurogenesis.At present,vagus nerve stimulation includes both invasive and non-invasive vagus nerve stimulation.Clinical studies have found that invasive vagus nerve stimulation combined with rehabilitation therapy is effective in im proving upper limb motor and cognitive abilities in stroke patients.Further clinical studies have shown that non-invasive vagus nerve stimulation,including ear/ce rvical vagus nerve stimulation,can stimulate vagal projections to the central nervous system similarly to invasive vagus nerve stimulation and can have the same effect.In this paper,we first describe the multiple effects of vagus nerve stimulation in stroke,and then discuss in depth its neuroprotective mechanisms in ischemic stroke.We go on to outline the res ults of the current major clinical applications of invasive and non-invasive vagus nerve stimulation.Finally,we provide a more comprehensive evaluation of the advantages and disadvantages of different types of vagus nerve stimulation in the treatment of cerebral ischemia and provide an outlook on the developmental trends.We believe that vagus nerve stimulation,as an effective treatment for stroke,will be widely used in clinical practice to promote the recovery of stroke patients and reduce the incidence of disability.

Working toward an integrated plasticity/network framework for repetitive transcranial magnetic stimulation to inform tailored treatments

Non-invasive brain stimulation techniques(NIBS),including repetitive transcranial magnetic stimulation(rTMS) and transcranial electric stim ulation(tES),are increasingly being adopted clinically for treatment of neuropsychiatric and neurological disorders,albeit with varying success.The rationale behind the use of NIBS has historically been that stim ulation techniques modulate neuronal activity in the targeted region and consequently induce plasticity which can lead to therapeutic outcomes.

Brain-wide activation involved in 15 mA transcranial alternating current stimulation in patients with first-episode major depressive disorder

Background Although 15 mA transcranial alternating current stimulation(tACS)has a therapeutic effect on depression,the activations of brain structures in humans accounting for this tACS configuration remain largely unknown.Aims To investigate which intracranial brain structures are engaged in the tACS at 77.5 Hz and 15 mA,delivered via the forehead and the mastoid electrodes in the human brain.Methods Actual human head models were built using the magnetic resonance imagings of eight outpatient volunteers with drug-naïve,first-episode major depressive disorder and then used to perform the electric field distributions with SimNIBS software.Results The electric field distributions of the sagittal,coronal and axial planes showed that the bilateral frontal lobes,bilateral temporal lobes,hippocampus,cingulate,hypothalamus,thalamus,amygdala,cerebellum and brainstem were visibly stimulated by the 15 mA tACS procedure.Conclusions Brain-wide activation,including the cortex,subcortical structures,cerebellum and brainstem,is involved in the 15 mA tACS intervention for first-episode major depressive disorder.Our results indicate that the simultaneous involvement of multiple brain regions is a possible mechanism for its effectiveness in reducing depressive symptoms.