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The N-methyl-d-aspartate receptor (NMDAR) hypofunction hypothesis has been proposed to help understand the etiology and pathophysiology of schizophrenia. This hypothesis was based on early observations that NMDAR antagonists could induce a full range of symptoms of schizophrenia in normal human subjects. Accumulating evidence in humans and animal studies points to NMDAR hypofunctionality as a convergence point for various symptoms of schizophrenia. Here we review animal models of NMDAR hypofunction generated by pharmacological and genetic approaches, and how they relate to the pathophysiology of schizophrenia. In addition, we discuss the limitations of animal models of NMDAR hypofunction and their potential utility for therapeutic applications.

N-methyl-D-aspartate receptors (NMDARs) are glutamate receptors with key roles in synaptic communication and plasticity. The activation of synaptic NMDARs initiates plasticity and stimulates cell survival. In contrast, the activation of extrasynaptic NMDARs can promote cell death underlying a potential mechanism of neurodegeneration occurring in Alzheimer’s disease (AD). The distribution of synaptic versus extrasynaptic NMDARs has emerged as an important parameter contributing to neuronal dysfunction in neurodegenerative diseases including AD. Here, we review the concept of extrasynaptic NMDARs, as this population is present in numerous neuronal cell membranes but also in the membranes of various non-neuronal cells. Previous evidence regarding the membranal distribution of synaptic versus extrasynaptic NMDRs in relation to AD mice models and in the brains of AD patients will also be reviewed.

The NMDA receptor (NMDAR) is known to transmit important information by conducting calcium ions. However, some recent studies suggest that activation of NMDARs can trigger synaptic plasticity in the absence of ion flow. Does ligand binding transmit information to signaling molecules that mediate synaptic plasticity? Using Förster resonance energy transfer (FRET) imaging of fluorescently tagged proteins expressed in neurons, conformational signaling is identified within the NMDAR complex that is essential for downstream actions. Ligand binding transiently reduces FRET between the NMDAR cytoplasmic domain (cd) and the associated protein phosphatase 1 (PP1), requiring NMDARcd movement, and persistently reduces FRET between the NMDARcd and calcium/calmodulin-dependent protein kinase II (CaMKII), a process requiring PP1 activity. These studies directly monitor agonist-driven conformational signaling at the NMDAR complex required for synaptic plasticity.

The appropriate display of social behaviors is essential for the well-being, reproductive success and survival of an individual. Deficits in social behavior are associated with impaired N-methyl-D-aspartate (NMDA) receptor-mediated neurotransmission. In this review, we describe recent studies using genetically modified mice and pharmacological approaches which link the impaired functioning of the NMDA receptors, especially of the receptor subunits GluN1, GluN2A and GluN2B, to abnormal social behavior. This abnormal social behavior is expressed as impaired social interaction and communication, deficits in social memory, deficits in sexual and maternal behavior, as well as abnormal or heightened aggression. We also describe the positive effects of pharmacological stimulation of the NMDA receptors on these social deficits. Indeed, pharmacological stimulation of the glycine-binding site either by direct stimulation or by elevating the synaptic glycine levels represents a promising strategy for the normalization of genetically-induced, pharmacologically-induced or innate deficits in social behavior. We emphasize on the importance of future studies investigating the role of subunit-selective NMDA receptor ligands on different types of social behavior to provide a better understanding of the underlying mechanisms, which might support the development of selective tools for the optimized treatment of disorders associated with social deficits.

IntroductionN-Methyl-D-Aspartate Receptor (NMDAR) hypofunction is hypothesised to underlie psychosis but this has not been tested early in illness.ObjectivesOur aim was to determine if NMDAR availability was lower in patients with first episode psychosis compared to healthy controls.MethodsTo address this, we studied 40 volunteers (21 patients with first episode psychosis and 19 matched healthy controls) using PET imaging with an NMDAR selective ligand, [18F]GE179, that binds to the ketamine binding site to index its distribution volume ratio (DVR) and volume of distribution (VT). Striatal glutamatergic indices (glutamate and Glx) were measured simultaneously using magnetic resonance spectroscopy imaging (1H-MRS).ResultsHippocampal DVR, but not VT, was significantly lower in patients relative to controls (p=0.02, Cohen’s d=0.81; p=0.15, Cohen’s d=0.49), and negatively associated with total (rho=-0.47, p= 0.04), depressive (rho=-0.67, p=0.002), and general symptom severity (rho=-0.74, p<0.001). Exploratory analyses found no significant differences in other brain regions (anterior cingulate cortex, thalamus, striatum and temporal cortex). We found an inverse relationship between hippocampal NMDAR availability and striatal glutamate levels in people with first-episode psychosis (rho = -0.74, p <0.001) but not in healthy controls (rho = -0.22, p = 0.44).ConclusionsThese findings are consistent with the NMDAR hypofunction hypothesis and identify the hippocampus as a key locus for relative NMDAR hypofunction, although further studies should test specificity and causality.DisclosureNo significant relationships.

The purpose of this study was to investigate the association of neutrophil percentage-to-albumin ratio (NPAR) with the severity at admission and discharge (short-term prognosis) in patients with anti-N-methyl-D-aspartic acid receptor (NMDAR) encephalitis. Multivariable logistic regression models such as NPAR were constructed based on univariable regression results. Receiver operating characteristic (ROC) curves, nomograms, and concordance index (c-index) were used to evaluate the efficacy of the models in assessing disease severity at admission and predicting short-term prognosis, validated by bootstrap, Hosmer-Lemeshow goodness-of-fit test, calibration curves, and decision curve analysis. A total of 181 patients with anti-NMDAR encephalitis diagnosed at the First Affiliated Hospital of Zhengzhou University were included. The results showed that NPAR had good sensitivity and specificity in assessing disease severity at admission and predicting short-term prognosis. The multivariable logistic regression models based on NPAR and other influencing factors had good discrimination, consistency, accuracy, calibration ability, applicability, and validity in assessing the severity at admission and predicting short-term prognosis. NPAR has good clinical value in assessing disease severity at admission and predicting short-term prognosis of patients with anti-NMDAR encephalitis.

To elucidate the influence of sex differences on the clinical characteristics of anti-NMDAR encephalitis during the acute phase. Patients diagnosed with anti-NMDAR encephalitis who were hospitalized at Huanhu Hospital, affiliated with Tianjin University, from January 2020 to January 2025 were collected. They were divided into two groups: male and female. Clinical data for both groups were gathered, including age, history of prodromal infection, clinical manifestations, complications, presence of tumor, laboratory indices, MRI findings, GCS scores, length of hospital stay, treatment regimens, and acute phase outcomes. Statistical methods were employed to compare the differences between the two groups. A total of 43 patients with anti-NMDAR encephalitis were included in this study, comprising 20 male patients (46.51%) and 23 female patients (53.49%). Female patients were more likely to exhibit decreased levels of consciousness compared to male patients (  = 4.113,  = 0.043). Additionally, the antibody titers in CSF of female patients were significantly higher than those in male patients too (  = -2.870,  = 0.004). Interestingly, CSF protein levels were higher in male patients than in female patients (  = -2.591,  = 0.019), and male patients were more prone to test positive for anti-MOG antibodies (  = 5.715,  = 0.017). The treatment improvement rate for female patients was lower than that for male patients (  = 4.768,  = 0.029), and family members of female patients were more likely to automatic discharge (  = 4.075,  = 0.044). Female patients with anti-NMDAR encephalitis experience greater challenges and difficulties compared to male patients. Therefore, it is necessary to choose more proactive treatment options for female patients to help reduce the risk of adverse outcome in acute phase.

Background Postoperative cognitive decline (POCD) is a recognized clinical phenomenon characterized by cognitive impairments in patients following anesthesia and surgery, yet its underlying mechanism remains unclear. Brain-derived neurotrophic factor (BDNF) plays an important role in neuronal plasticity, learning, and memory via activation of TrkB-full length (TrkB-FL) receptors. It has been reported that an abnormal truncation of TrkB mediated by calpain results in dysregulation of BDNF/TrkB signaling and is associated with cognitive impairments in several neurodegenerative disorders. Calpains are Ca 2+ -dependent proteases, and overactivation of calpain is linked to neuronal death. Since one source of intracellular Ca 2+ is N-methyl-d-aspartate receptors (NMDARs) related and the function of NMDARs can be regulated by neuroinflammation, we therefore hypothesized that dysregulation of BDNF/TrkB signaling mediated by NMDAR/Ca 2+ /calpain might be involved in the pathogenesis of POCD. Methods In the present study, 16-month-old C57BL/6 mice were subjected to exploratory laparotomy with isoflurane anesthesia to establish the POCD animal model. For the interventional study, mice were treated with either NMDAR antagonist memantine or calpain inhibitor MDL-28170. Behavioral tests were performed by open field, Y maze, and fear conditioning tests from 5 to 8 days post-surgery. The levels of Iba-1, GFAP, interleukin-1β (IL-1β), IL-6, tumor necrosis factor-α (TNF-α), NMDARs, calpain, BDNF, TrkB, bax, bcl-2, caspase-3, and dendritic spine density were determined in the hippocampus. Results Anesthesia and surgery-induced neuroinflammation overactivated NMDARs and then triggered overactivation of calpain, which subsequently led to the truncation of TrkB-FL, BDNF/TrkB signaling dysregulation, dendritic spine loss, and cell apoptosis, contributing to cognitive impairments in aging mice. These abnormities were prevented by memantine or MDL-28170 treatment. Conclusion Collectively, our study supports the notion that NMDAR/Ca2+/calpain is mechanistically involved in anesthesia and surgery-induced BDNF/TrkB signaling disruption and cognitive impairments in aging mice, which provides one possible therapeutic target for POCD.

This study reported a case of overlapping anti-N-methyl-D-aspartate receptor (NMDAR) encephalitis and myelin oligodendrocyte glycoprotein (MOG) inflammatory demyelinating disease with human herpesviruses 7 (HHV-7) infection. The detailed clinical characteristics, neuroimaging features, and outcomes of the patient were collected. Polymerase chain reaction (PCR), cell-based assay (CBA) and the tissue-based indirect immunofluorescence assay (TBA) were used for diagnosis. The clinical manifestations included headache, dizziness, fever, optic neuritis, and epileptic-seizures. Brain magnetic resonance imaging (MRI) showed hyperintensities involving the left frontal, orbital gyrus and bilateral optic nerve with substantial contrast enhancement. Moreover, test for HHV-7 DNA by using the next generation sequencing metagenomics and polymerase chain reaction showed positive result in CSF but not in the serum samples. Anti-HHV-7 IgM and IgG antibodies were detected in both the serum and cerebrospinal fluid. NMDAR antibodies (1:10) were found positive in the patient's CSF by a cell-based assay, and MOG antibodies were positive in the serum (1:10) and CSF (1:32). The patient appeared to respond well to immune therapy and it was found that the clinical symptoms including epileptic-seizure as well as headache were relieved and cerebral lesions almost disappeared after the treatment. However, his vision was not completely restored even at the 8-month follow-up, especially the vision in his right eye which was more seriously damaged. We report a rare case of MOG antibodies and anti-NMDAR encephalitis overlapping syndrome (MNOS) with HHV-7 infection for the first time. The possibility of MNOS needs be considered when optic neuritis occurs in the patients diagnosed with anti-NMDAR encephalitis. Besides, immunotherapy should be initiated as early as possible to improve the treatment outcomes and facilitate complete cure.

Background Four published case reports have proposed Lyme neuroborreliosis (LNB) as a trigger for anti-N-methyl-D-aspartate receptor (anti-NMDAR) encephalitis. In this study, we examined the prevalence of anti-NMDAR antibodies in a well-characterized cohort of patients with LNB. Methods In this retrospective cohort study, archived cerebrospinal fluid (CSF) samples from patients diagnosed with LNB between 2001 and 2012 were analyzed for anti-NMDAR IgG using a standard commercial cell-based assay. LNB diagnosis followed the European Federation of Neurological Societies guidelines. To identify potential later development of anti-NMDAR encephalitis, an infectious disease specialist systematically reviewed medical records in 2021, and the national reference center for neural autoantibody testing verified testing history in 2025. Results We included 82 patients with a median age of 52 years (interquartile range [IQR]: 34–63); 55% were male. Median symptom duration before diagnosis was 21 days (IQR: 7–45). The most frequent symptoms were cranial nerve palsy (51%) and radiating pain (50%). Among 70 patients with available CSF data, limited by access to laboratory records, the median CSF leukocyte count was 124 × 10 6 cells/L (IQR: 61–236). None of the 82 CSF samples tested positive for anti-NMDAR antibodies, resulting in an estimated prevalence of 0% (95% CI: 0.0–4.4). No patients were clinically suspected of autoimmune encephalitis or tested for it. Conclusion Anti-NMDAR antibodies were not detected in the CSF of LNB patients, suggesting their presence is rare in this population at diagnosis. Although the sample size may limit statistical power, the absence of later clinical suspicion or testing supports the hypothesis that LNB is an uncommon trigger for anti-NMDAR encephalitis.