Japanese encephalitis-induced anti-N-methyl-d-aspartate receptor encephalitis: A hospital-based prospective study

ObjectivesA hospital-based prospective study was performed to determine: 1) whether Japanese encephalitis (JE) normally triggers anti-N-methyl-d-aspartate receptor (NMDAR) immunoglobulin G (IgG) synthesis, especially in monophasic JE patients; and 2) the incidence of JE-induced anti-NMDAR encephalitis in pediatric patients with JE.MethodsWe detected the level of anti-NMDAR IgG in the serum and cerebral spinal fluid (CSF) of JE patients within one week of onset. If patients relapsed during the convalescence phase, we detected JE virus RNA in the CSF and anti-NMDAR IgG in both the serum and CSF. For patients who did not relapse during the convalescence phase, serum was collected and anti-NMDAR IgG was detected during the 30–60-day course of the disease.ResultsWe enrolled 65 JE patients, who were negative for anti-NMDAR IgG in the serum and CSF during the acute phase, of which 63 patients were successfully followed up. Five patients relapsed during the convalescence phase, for whom JE virus RNA in the CSF was negative and excluded latent JE reactivation. The distinctive symptoms of four younger patients were choreoathetosis, whereas the psychiatric and behavioral manifestations were the distinctive symptoms experienced by the teenager. Anti-NMDAR IgG in the CSF of three patients was positive and they were diagnosed with anti-NMDAR encephalitis. The other two patients were negative for anti-NMDAR IgG in both the serum and CSF. For the 58 patients who did not relapse during the convalescence phase, anti-NMDAR IgG was negative in the serum of all patients at 30–60 days during the course of the disease.ConclusionsJE does not typically trigger anti-NMDAR IgG synthesis. Besides anti-NMDAR IgG, other unknown autoantibodies can also cause autoimmune encephalitis in the convalescence phase of JE. The incidence of JE-induced autoimmune encephalitis in pediatric patients with JE was 7.9%, and the incidence of JE-induced anti-NMDAR encephalitis was 4.7%.     

Relapsing Anti-NMDAR Encephalitis after a gap of eight years in a girl from North-East India

It has been just 7 years since the discovery of anti-NMDAR encephalitis as distinct immune-mediated encephalitis and we have such cases being reported from our country. Herein, we describe a case of a 13-year-old girl who had relapsing encephalitis consisting of multiple types of difficult-to-control seizures, abnormal behavior, language disintegration, memory loss and abnormal movements eight years after the first clinical attack. In 2005, when she was 5 yearsold, anti-NMDAR encephalitis was not yet discovered and she was provisionally diagnosed as a case of viral encephalitis. During her second attack in 2013, antibodies against NMDAR were demonstrated by immunofluoresence in serum (1:10). This is the first report from our country of a case of relapsing anti-NMDAR encephalitis of such a long duration, successfully treated by immunotherapy.     

Altered perception might be a symptom of anti-N-methyl-D-aspartate receptor (NMDAR) encephalitis

ABSTRACT

Most patients with N-methyl-D-aspartate receptor (NMDAR) encephalitis initially present with psychiatric symptoms. Although a delayed diagnosis may lead to a poor outcome, psychiatric symptoms that could differentiate anti-NMDAR encephalitis from other psychoses have not been fully investigated. We evaluated two patients with anti-NMDAR encephalitis who were observed by psychiatrists from onset throughout the course of disease. Both patients exhibited disorientation, memory deficits, perceptual disturbances, hallucinations, and mood liability. Among those, altered perceptions were most prominent - in particular, altered time perceptions without disorganization syndrome. The information obtained for these patients may help clinicians differentiate anti-NMDAR encephalitis from other psychoses, e.g., schizophrenia.     

抗NMDAR脑炎血清抗NMDAR抗体阴性患者临床分析

目的 探讨血清抗N-甲基-D-天冬氨酸受体(NMDAR)抗体阴性的抗NMDAR脑炎患者的临床表现特征、治疗及其预后特点.方法 收集郑州大学第一附属医院2013-09—2019-12确诊为抗NMDAR脑炎的60例患者,根据其血清中抗NMDAR抗体的情况分为血清抗体阴性组和阳性组,分析2组临床表现特征、辅助检查、治疗及预后...     

Absent anti-N-methyl-D-aspartate receptor NR1a antibodies in herpes simplex virus encephalitis and varicella zoster virus infections

Purpose: A 2012 report and subsequent case series described anti-N-methyl-D-aspartate receptor (NMDAR) antibodies in patients during the acute phase and relapse of herpes simplex virus 1 (HSV1) encephalitis (HSV1E). However, the prevalence of this phenomenon is unknown and systematic studies on other viral infections of the nervous system are missing. Materials and methods: We retrospectively analyzed serial cerebrospinal fluid (CSF) and serum samples of consecutive patients treated for neurological HSV1, HSV2 and varicella zoster virus (VZV) infections in our tertiary care university hospital between 2003 and 2013 for the presence of antibodies directed against the NR1a subunit of the NMDAR using indirect immunofluorescence. Results: In total, 88 patients with the following infections were identified through an electronic database search: HSV1 (24 with encephalitis), HSV2 (6 with meningitis, 3 with encephalitis and 1 with myelitis), or VZV (3 with meningitis, 33 with encephalitis, 17 with radiculitis and 1 with myelitis). Two patients with HSV1E and HSV2E, respectively, experienced a clinical relapse. Clinical follow-up was for up to 85 months, and repetitive serum and CSF analyses for up to 43 months. However, at no time did any of the 88 patients exhibit anti-NMDAR NR1a antibodies. Conclusions: In this study, we did not detect anti-NMDAR NR1a antibodies in serial CSF and serum samples of HSV1E patients or patients with other viral infections (HSV2 and VZV). However, the presence of antibodies directed against other epitopes of the NMDAR and other neuronal cell surface antigens cannot be excluded, necessitating further studies.     

晚发型抗N-甲基-D-天冬氨酸受体脑炎临床特征分析

目的分析晚发型抗N-甲基-D-天冬氨酸受体(NMDAR)脑炎的临床特征。方法收集2010-01-01—2019-05-01于郑州大学第一附属医院住院确诊为抗NMDAR脑炎的患者临床资料,分析晚发型(≥50岁)患者数据,并与早发型(18~49岁)患者进行对比。结果18例晚发型患者中,男11例(61%),发病年龄50~84岁。晚发型患者中,9例(50%)患者出现前驱症状,精神行为异常是最常见的首发症状(44%)和临床表现(78%);头颅磁共振提示脑实质炎性病变9例(9/17,53%);脑脊液检验结果异常17例(94%);合并肿瘤4例(22%),均非畸胎瘤。相比于早发组患者,晚发组患者有更高的自主神经功能障碍比例(72%vs 45%,P=0.032),更高的岛叶病变比例(67%vs 27%,P=0.047),更高的脑脊液蛋白升高比例(56%vs 28%,P=0.023),以及更高的脑脊液鞘内IgG合成率升高比例(73%vs 44%,P=0.041)。晚发组合并肿瘤均非畸胎瘤,早发组合并肿瘤均为畸胎瘤(P=0.001)。结论相比早发型抗NMDAR脑炎患者,晚发型患者更易出现岛叶病变,更易出现脑脊液炎症反应,其发病机制可能与畸胎瘤不相关。     

Long-term potentiation in the presence of NMDA receptor antagonist arylalkylamine spider toxins

The role of the NMDA receptor (NMDAR) in long-term potentiation (LTP) is now well established. All potent NMDAR antagonists known to date inhibit the induction of LTP at the Schaffer collateral-CA1 pyramidal cell synapse in rat hippocampus, regardless of their site and mechanism of action. Arylalkylamine toxins are noncompetitive NMDAR antagonists in the mammalian central nervous system (CNS). The synthetic toxins argiotoxin-636 (Arg-636), Joro spider toxin (JSTX-3), alpha-agatoxin-489 and -505 (Agel-489 and Agel-505) and philanthotoxin-433 (delta-PhTX) were found in the present study to have no effect on the induction of LTP in the Schaffer collateral-CA1 pyramidal cell pathway in rat hippocampal slices maintained in vitro. Arylalkylamine toxins represent a class of potent NMDAR antagonists that fail to affect hippocampal LTP, and thus provide novel structural leads for the development of NMDAR antagonists that do not impair cognition.     

抗NMDA受体脑炎45例特点和临床转归分析

目的探讨本组抗NMDA受体脑炎患者的临床特点。方法收集北京丰台右安门医院和北京宣武医院神经内科2012年10月至2015年4月收治的45例抗NMDA受体脑炎患者的临床资料,分析病例特点,随访病情转归。结果本组的45例患者年龄为14~61岁,平均年龄32.2±13.24岁;男性27例,其中3例(11%)合并肿瘤。女性18例,其中5例(28%)合并卵巢畸胎瘤。23例(51%)出现前驱症状。本组45例临床症状表现为精神症状(91%)、癫痫发作(76%)、不自主运动(42%)、中枢性低通气(24%)、意识水平下降(47%)及自主神经功能障碍(40%)。脑脊液(CSF)常规、生化检查阳性率为89%,所有患者CSF抗NMDA受体抗体阳性。脑电图(EEG)多表现为双额、颞、中央导联为主的轻度(21%)至中度(59%)慢波。53%患者头颅CT平扫或MRI检查有异常表现,多见于额颞叶T2-Flair异常信号。所有患者均给予激素和丙种球蛋白治疗,6例患者接受环磷酰胺或吗替麦考酚治疗。除1例失访,44例患者预后良好(MRS评分0-2分)者占86%。结论抗NMDAR脑炎发病男性并不少见,肿瘤合并率低。以精神行为异常、癫痫发作、CSF抗NMDA受体抗体阳性为其主要临床特点。绝大部分患者EEG异常,并与病情严重程度相关。79%患者一线免疫治疗效果良好。8例合并肿瘤患者病情严重且预后不良,畸胎瘤摘除术不能完全预防该病发生,但能减轻病情严重程度。     

Diagnostic value of CSF findings in antibody-associated limbic and anti-NMDAR-encephalitis

PurposeIn people with suspected inflammatory CNS disease, cerebrospinal fluid (CSF) is commonly analyzed. Antibody-associated limbic encephalitis (ab-LE) and anti-NMDAR-encephalitis are recognized as two major syndromes of autoimmune epilepsies. Here, we investigated the diagnostic value of CSF findings in these two entities.MethodsWe reviewed patients from our tertiary epilepsy centre with ab-LE and anti-NMDAR-encephalitis in whom CSF examination including oligoclonal bands (OCB) was performed. Ab-LE patients were subdivided according to antibodies (voltage-gated potassium channels, VGKC; glutamic acid decarboxylase, GAD) or presence of onconeural antibodies/presence of tumour into three groups: VGKC-LE, GAD-LE or paraneoplastic LE (PLE). As controls, patients with CSF investigations in whom autoimmune origin was initially assumed but not confirmed later on were included. In addition, a review of published ab-LE and anti-NMDAR-encephalitis cases with reported CSF data was performed.Results55 ab-LE (23 VGKC-LE, 25 GAD-LE, 7 PLE) and 14 anti-NMDAR-encephalitis patients were identified at our centre. OCB were significantly more frequent in ab-LE and anti-NMDAR-encephalitis than in controls. Literature review identified 150 ab-LE and 95 NMDAR cases. Analysis of pooled data confirmed that presence of OCB was significantly more frequent in ab-LE and anti-NMDAR-encephalitis (especially in people with GAD-LE and anti-NMDAR encephalitis) as compared to controls. Sensitivity and specificity of OCB in the pooled ab-LE and anti-NMDAR-encephalitis patients was 34% and 96%, respectively. In patients with ab-LE and anti-NMDAR-encephalitis, the likelihood of OCB in CSF was 8.5-fold higher as compared to controls. Furthermore, in the pooled ab-LE and anti-NMDAR-encephalitis patients, cell counts in CSF were more frequently elevated (especially in those with anti-NMDAR encephalitis) than in controls, whereas protein content of CSF was not different between the groups.ConclusionOCB, and to a lesser extent cell counts in CSF, appear to be helpful additional CSF markers in the diagnostic evaluation of people presenting with a constellation suggestive for GAD-LE, PLE and anti-NMDAR-encephalitis, prompting subsequent analysis of specific antibodies.     

Late relapse of anti-N-methyl-d-aspartate receptor encephalitis with amusia and transiently reduced uptake in 123I-iomazenil single-photon emission computed tomography

IntroductionAnti-N-methyl-d-aspartate receptor (NMDAR) encephalitis has a high relapse rate at approximately 10–20%. Most relapses occur within 2 years from onset, and 5 years after onset is rare. We report a case of anti-NMDAR encephalitis relapse with amusia 10 years after the initial encephalitis and discuss the usefulness of ¹²³I-iomazenil single-photon emission computerized tomography (IMZ-SPECT) for its diagnosis.CaseA 13-year-old left-handed girl presented with a depressed level of consciousness and focal to bilateral tonic-clonic seizures. Cerebrospinal fluid (CSF) analysis showed a mildly increased white blood cell count, elevated neopterin levels, and positive oligoclonal bands. Brain MRI was normal. IMZ-SPECT revealed reduced uptake in the right frontoparietal region. She received intravenous pulse methylprednisolone (IVMP) and high-dose intravenous immunoglobulin for autoimmune encephalitis; her symptoms resolved without neurological deficits. At 23 years old, she had mild right-sided numbness, dysarthria, amusia, and tonic-clonic seizures. Although the CSF analysis and brain MRI were normal, IMZ-SPECT revealed reduced uptake, indicating a relapse of encephalitis. IVMP administration resolved the symptoms. After discharge, the initial and relapse CSF analysis revealed anti-NMDAR antibodies.ConclusionAn anti-NMDAR encephalitis relapse 10 years after onset has never been reported. IMZ-SPECT may help in the diagnosis of anti-NMDAR encephalitis.     

Anti-<Emphasis Type="Italic">N</Emphasis>-methyl-<Emphasis Type="SmallCaps">d</Emphasis>-aspartate receptor encephalitis: a common cause of encephalitis in the intensive care unit

Anti-N-methyl-d-aspartate receptor encephalitis (anti-NMDAR encephalitis) is the most common type of immune-mediated encephalitis. This study aimed to assess the incidence and mortality of anti-NMDAR encephalitis in intensive care unit (ICU) to evaluate the clinical manifestations, laboratory findings, managements and outcomes, and to compare these characteristics with patients with non-anti-NMDAR encephalitis admitted to ICU. Patients admitted to the neurological ICU with suspected encephalitis were included between January 1, 2012 and July 31, 2015. Cerebrospinal fluid (CSF) of enrolled patients was screened for anti-NMDAR antibodies using a cell-based assay. 72 critically ill patients with encephalitis of uncertain etiology were investigated, and 16 patients were positive for anti-NMDAR antibodies in CSF. Compared to patients with non-anti-NMDAR encephalitis, patients with anti-NMDAR encephalitis were younger, more likely to present with the psychiatric symptoms, dyskinesia, and autonomic dysfunction, and had longer ICU stays. The abnormal movements were so difficult to control that complicated the management. The outcome was favorable in ten patients 1 year after the disease onset, and the mortality was as high as 25 % overall. The incidence of anti-NMDAR encephalitis is high among critically ill patients with encephalitis of uncertain etiology. Controlling dyskinesia proved to be a challenge. Persistent dysautonomias were additional difficult to manage confounders. Same points being highlighted in this study may aid clinicians in the management of patients with anti-NMDAR encephalitis in intensive care practice.     

Arterial spin labeling perfusion imaging in an infant with anti-N-methyl-D-aspartate receptor encephalitis: A case report

BackgroundAnti-N-methyl-d-aspartate receptor (NMDAR) encephalitis is an autoimmune encephalitis characterized by complex neuropsychiatric syndromes and the presence of cerebrospinal fluid (CSF) antibodies against NMDAR. The characteristics of anti-NMDAR encephalitis in children, particularly infants, are unclear due to difficulties in neurologic assessment such as psychiatric symptoms. Additionally, subtle or non-specific findings of conventional magnetic resonance imaging (MRI) make early diagnosis even more difficult. Herein, we present the first case of infant anti-NMDAR encephalitis in which perfusion imaging demonstrated marked abnormalities and the absence of conventional MRI findings.Case presentationThe patient was an 11-month-old boy who was admitted because of seizure and prolonged fever. He presented with involuntary movements of the mouth and tongue. Brain MRI showed no morphological abnormalities, but three-dimensional arterial spin labeling (ASL) perfusion imaging showed reduced blood flow in the left temporal and frontal regions and the right cerebellum. After that, a positive anti-NMDAR antibody test result was received. Despite treatment with IVIG and methylprednisolone, the involuntary movements and autonomic dysfunction gradually became more prominent. After rituximab administration, the clinical symptoms improved slightly, and follow-up MRI revealed diffuse brain atrophy and improvement in the balance of brain perfusion.ConclusionsTo the best of our knowledge, this is the first case report of infantile anti-NMDAR encephalitis in which cerebral blood flow was evaluated using three-dimensional ASL perfusion imaging. Indeed, our case, which showed abnormalities only in ASL perfusion imaging, suggests that CBF assessment could aid in the early diagnosis of anti-NMDAR encephalitis in infants.     

Japanese encephalitis can trigger anti-<Emphasis Type="Italic">N</Emphasis>-methyl-<Emphasis Type="SmallCaps">d</Emphasis>-aspartate receptor encephalitis

Japanese encephalitis (JE) is usually a monophasic disease; however, in rare cases, patients with JE may have an early relapse after a partial recovery, giving rise to a biphasic pattern for the disease. In this study, we report three pediatric cases in which post-JE relapse was characterized by movement disorder and/or behavioral problems, and was related to anti-N-methyl-d-aspartate receptor (NMDAR) immunoglobulin G (IgG). Serum and cerebrospinal fluid were examined for anti-NMDAR IgG in three patients who had confirmed JE and then developed relapsing symptoms which were similar to those of anti-NMDAR encephalitis. The main symptoms of the two young children were choreoathetosis, irritability, and sleep disorder; while for the teenager, agitation, mutism, rigidity, and sleep disorder were the main symptoms. Samples of cerebrospinal fluid from all patients were positive for anti-NMDAR IgG, and all patients gradually improved with immunotherapy. Testing for NMDAR antibodies is highly recommend in patients with JE, especially those with a relapsing syndrome involving movement disorder and/or behavioral problems, as these patients may benefit from immunotherapy.     

抗N-甲基-D-天冬氨酸受体脑炎的抗体检测及临床意义

目的探讨抗N-甲基-D-天冬氨酸受体(NMDAR)脑炎的抗体检测意义及临床特征。方法选取本院收治的脑炎病人35例及对照组30例,分析临床资料,采用转染细胞间接免疫荧光法检测两组患者其血清及脑脊液抗NMDAR机体结果抗NMDAR抗体检测仅1例边缘叶脑炎患者结果阳性,该患者腑脊液细胞数增多、蛋白轻度升高、脑电图见双侧慢波、其余检查无异常。精神症状及意识水平障碍明显,免疫治疗有效。结论抗NMDAR脑炎发病率低,临床表现复杂多样,怀疑该病时需行抗NMDAR抗体检测。     

Anti-N-Methyl-D-Aspartate Receptor Encephalitis in Korea: Clinical Features,Treatment, and Outcome

Background and Purpose

Anti-N-methyl-D-aspartate receptor (anti-NMDAR) encephalitis is the most common type of autoimmune synaptic encephalitis and it often responds to treatment. We analyzed the clinical characteristics of anti-NMDAR encephalitis in Korea.

Methods

Serum and/or cerebrospinal fluid (CSF) of adult patients (aged ≥18 years) with encephalitis of undetermined cause were screened for anti-NMDAR antibodies using a cell-based indirect immunofluorescence assay. The patients came from 41 university hospitals.

Results

Of the 721 patients screened, 40 were identified with anti-NMDAR antibodies and clinical details of 32 patients were obtained (median age, 41.5 years; 15 females). Twenty-two patients (68.8%) presented with psychiatric symptoms, 16 (50%) with seizures, 13 (40.6%) with movement disorders, 15 (46.9%) with dysautonomia, 11 (34.4%) with memory disturbance, and 11 (34.4%) with speech disturbance. Magnetic resonance imaging, electroencephalography, and CSF examinations yielded nonspecific findings. Tumor information was only available for 22 patients: 5 patients had tumors, and 2 of these patients had ovarian teratomas. Twenty-two patients received immunotherapy and/or surgery, and therapeutic responses were analyzed in 21 patients, of which 14 (66.7%) achieved favorable functional outcomes (score on the modified Rankin Scale of 0-2).

Conclusions

This study investigated the clinical characteristics of adult anti-NMDAR encephalitis in Korea. Currently, elderly patients who do not have tumors are commonly diagnosed with this condition. Understanding the detailed clinical characteristics of this disease will improve the early detection of anti-NMDAR encephalitis in patients both young and old.     

Emergence of NMDAR-independent long-term potentiation at hippocampal CA1 synapses following early adolescent exposure to chronic intermittent ethanol: role for sigma-receptors

Adolescent humans who abuse alcohol are more vulnerable than adults to the development of memory impairments. Memory impairments often involve modifications in the ability of hippocampal neurons to establish long-term potentiation (LTP) of excitatory neurotransmission; however, few studies have examined how chronic ethanol exposure during adolescence affects LTP mechanisms in hippocampus. We investigated changes in LTP mechanisms in hippocamal slices from rats exposed to intoxicating concentrations of chronic intermittent ethanol (CIE) vapors in their period of early-adolescent (i.e., prepubescent) or late-adolescent (i.e., postpubescent) development. LTP was evaluated at excitatory CA1 synapses in hippocampal slices at 24 h after the cessation of air (control) or CIE vapor treatments. CA1 synapses in control slices showed steady LTP following induction by high-frequency stimulation, which was fully dependent on NMDAR function. By contrast, slices from early-adolescent CIE exposed animals showed a compound form of LTP consisting of an NMDAR-dependent component and a slow-developing component independent of NMDARs. These components summated to yield LTP of robust magnitude above LTP levels in age-matched control slices. Bath-application of the sigma-receptor antagonist BD1047 and the neuroactive steroid pregnenolone sulfate, but not acute ethanol application, blocked NMDAR-independent LTP, while leaving NMDAR-dependent LTP intact. Analysis of presynaptic function during NMDAR-independent LTP induction demonstrated increased presynaptic function via a sigma-receptor-dependent mechanism in slices from early-adolescent CIE-exposed animals. By contrast, CIE exposure after puberty onset in late-adolescent animals produced decrements in LTP levels. The identification of a role for sigma-receptors and neuroactive steroids in the development of NMDAR-independent LTP suggests an important pathway by which hippocampal synaptic plasticity, and perhaps memory, may be uniquely altered by chronic ethanol exposure during the prepubescent phase of adolescent development.     

Anti-NMDAR autoimmune encephalitis

The N-methyl-d-aspartate receptor (NMDAR) is involved in normal physiological and pathological states in the brain. Anti-NMDAR encephalitis is characterized by memory deficits, seizures, confusion, and psychological disturbances in males and females of all ages. This type of encephalitis is often associated with ovarian teratoma in young women, but children are less likely to have tumors. Anti-NMDAR encephalitis is a neuroimmune syndrome in patients with autoantibodies recognizing extracellular epitopes of NMDAR, and the autoantibodies attenuate NMDAR function through the internalization of NMDAR. Following the initial symptoms of inflammation, the patients show the various symptoms such as memory loss, confusion, emotional disturbances, psychosis, dyskinesis, decrease in speech intelligibility, and seizures. About half of these patients improved with immunotherapy including high-dose intravenous corticosteroids and intravenous immunoglobulins is administrated to these patients, but the patients who had no improvement with these therapy require further treatments with rituximab or cyclophosphamide. It is necessary to detect anti-NMDAR antibodies at early stages, because the prognosis of these patients may be improved by early treatment. Recovery is slow, and the patients may have some disturbances in their motor function and cognition. The pathologic mechanism underlying the development of anti-NMDAR encephalitis has been elucidated gradually, but the optimal treatment has not yet been clarified. Further studies are required to clarify in detail the mechanism underlying anti-NMDA encephalitis and to develop effective treatments.     

Anti-N-Methyl-D-Aspartate Encephalitis With Ovarian Cystadenofibroma

We report the case of an adolescent girl with anti-N-methyl-D-aspartate-receptor (NMDAR) encephalitis who presented with focal seizures and hemichorea, followed by agitation, speech disturbance, mutism, and autonomic dysfunction. The institution of immunotherapy and removal of an ovarian cystadenofibroma led to full resolution of her symptoms with disappearance of serum NMDAR antibodies. This is the first report linking ovarian cystadenofibroma to anti-NMDAR encephalitis.     

In vivo administration of granulocyte colony‐stimulating factor restores long‐term depression in hippocampal slices prepared from transgenic APP/PS1 mice

Granulocyte colony‐stimulating factor (G‐CSF) is a hematopoietic cytokine that also possesses neurotrophic and antiapoptotic properties. G‐CSF has been reported to decrease amyloid burden significantly, promote hippocampal neurogenesis, and improve spatial learning in a mouse model of Alzheimer's disease. To understand better the effects of G‐CSF on hippocampal‐dependent learning, the present study focused on electrophysiological correlates of neuroplasticity, long‐term potentiation (LTP), and long‐term depression (LTD). Two cohorts of transgenic APP/PS1 mice, with or without prior bone marrow transplantation from Tg GFP mice, were treated in vivo for 2 weeks with G‐CSF or vehicle. After completion of the treatments, hippocampal slices were prepared for electrophysiological studies of LTP and LTD. LTP was induced and maintained in both G‐CSF‐treated and vehicle‐treated groups of Tg APP/PS1. In contrast, LTD could not be induced in vehicle‐treated Tg APP/PS1 mice, but G‐CSF treatment restored LTD. The LTP and LTD results obtained from the cohort of bone marrow‐grafted Tg APP/PS1 mice did not differ from those from nongrafted Tg APP/PS1 mice. The mechanism by which G‐CSF restores LTD is not known, but it is possible that its capacity to reduce amyloid plaques results in increased soluble oligomers of amyloid‐β (A‐β), which in turn may facilitate LTD. This mechanism would be consistent with the recent report that soluble A‐β oligomers promote LTD in hippocampal slices. © 2014 Wiley Periodicals, Inc.     

β-Estradiol unmasks metabotropic receptor-mediated metaplasticity of NMDA receptor transmission in the female rat dentate gyrus

Loss of estrogen in women following menopause is associated with increased risk for cognitive decline, dementia and depression, all of which can be prevented by estradiol replacement. The dentate gyrus plays an important role in cognition, learning and memory. The gatekeeping function of the dentate gyrus to filter incoming activity into the hippocampus is modulated by estradiol in a frequency-dependent manner and involves activation of metabotropic glutamate receptors (mGluR). In the present study, we investigated whether estradiol (EB) modulates the metaplastic effect of inducing synaptic long-term potentiation (LTP) on subsequent propensity for expression of LTP in the dentate gyrus. At medial perforant path-dentate granule cell synapses in hippocampal slices of ovariectomized female rats, EB replacement was critical for an initial induction of LTP to enhance the magnitude of subsequent LTP elicited by a second high-frequency stimulation, metaplasticity, which was not present in slices from oil-treated control animals. EB enhanced expression of group I mGluRs, and the metaplastic effect of EB on LTP required activation of group I mGluRs that led to Src-family tyrosine kinase-mediated phosphorylation of NR2B subunits of N-methyl-d-aspartate receptors (NMDAR) that enhanced the magnitude of NMDAR-dependent LTP. Our data show that EB effects on LTP in the hippocampal dentate gyrus require activation of group I mGluRs, which in turn leads to functional metaplastic regulation of NR2B subunit-containing NMDARs, as opposed to direct effects of EB on NMDARs.