Effect of Xingnaojing Injection(醒脑静注射液)on Hippocampal N-methyl-D-aspartic Acid Receptors of Focal Cerebral Ischemia in Rats

Objective: To observe and elucidate the neuroprotective effect of Xingnaojing (XNJ) injection on hippocampal N-methyl-D-aspartic acid (NMDA) receptors of focal cerebral ischemia in rats. Methods: Cerebral ischemia was established by occluding the middle cerebral artery with an intraluminal suture technique in rats. Neurological deficit score, infarct volume and quantity of NMDA receptors were estimated in all groups and compared. Results: After being treated with XNJ, the score decreased in the initial 6 hours and infarct volume decreased in 24 hours. And within 24 hours, the quantity of NMDA receptors obviously decreased compared with the model group (P<0. 01) It indicated that XNJ could ameliorate neurological behavior of middle cerebral artery occlusion rats and down-regulate the expression of hippocampal NMDA receptors. Conclusion: The neuroprotective effect of XNJ on focal cerebral ischemia is possibly related to down-regulating the expression of NMDA receptors in rats.

Water-soluble lipopolymer delivery of N-methyl-D-aspartic acid receptor 2B siRNA relieves chronic neuropathic pain in rats

Spinal dorsal horn N-Methyl-D-aspartic acid receptor 2B （NR2B） overexpression plays an important role in the production and maintenance of neuropathic pain. Because small interfering RNA （siRNA） can inhibit NR2B expression, siRNA may provide a novel approach to treat neuropathic pain and possibly nerve injury. However, an efficient and safe vector for NR2B siRNA has not been discovered. This study shows that a water soluble lipopolymer （WSLP） comprised of low molecular weight polyethyleneimine （PEI） and cholesterol can deliver siRNA targeting NR2B for the treatment of neuropathic pain. Results show that intrathecal injection of WSLP/siRNA complexes for 3 days inhibit NR2B gene expression with reductions in mRNA and protein levels by 59% and 54%, respectively, compared with control rats （P 〈 0.01）. Injection of WSLP complexed with scrambled siRNA, or PEI with siRNA did not show this inhibitory effect. Moreover, injection of WSLP/siRNA complexes significantly relieved neuropathic pain at 3, 7, 12, and 21 days, while injection of WSLP with scrambled siRNA or PEI with siRNA did not. These results demonstrate that WSLP can efficiently deliver siRNA targeting NR2B in vivo and relieve neuropathic pain.

Comparison of three administration modes for establishing a zebrafish seizure model induced by N-Methyl-D-aspartic acid

BACKGROUND Epilepsy is a complex neurological disorder characterized by recurrent,unprovoked seizures resulting from the sudden abnormal discharge of brain neurons.It leads to transient brain dysfunction,manifested by abnormal physical movements and consciousness.It can occur at any age,affecting approximately 65 million worldwide,one third of which are still estimated to suffer from refractory seizures.There is an urgent need for further establishment of seizure models in animals,which provides an approach to model epilepsy and could be used to identify novel anti-epileptic therapeutics in the future.AIM To compare three administration modes for establishing a seizure model caused by N-Methyl-D-aspartic acid(NMDA)in zebrafish.METHODS Three administration routes of NMDA,including immersion,intravitreal injection and intraperitoneal injection,were compared with regard to their effects on inducing seizure-like behaviors in adult zebrafish.We evaluated neurotoxicity by observing behavioral changes in zebrafish and graded those behaviors with a seizure score.In addition,the protective effects of MK-801(Dizocilpine)and natural active constituent resveratrol against NMDA-induced alterations were studied.RESULTS The three NMDA-administration methods triggered different patterns of the epileptic process in adult zebrafish.Seizure scores were increased after increasing NMDA concentration regardless of the mode of administration.However,the curve of immersion continuously rose to a high plateau(after 50 min),while the curves of intravitreal injection and intraperitoneal injection showed a spike in the early stage(10-20 min)followed by a steady decrease in seizure scores.Furthermore,pretreatment with resveratrol and MK-801 significantly delayed seizure onset time and lowered seizure scores.CONCLUSION By comparing the three methods of administration,intravitreal injection of NMDA was the most suitable for establishing an acute epileptic model in zebrafish.Thus,intraperitoneal injection in zebrafish can be applied to simulate diseases such as epilepsy.In addition,NMDA immersion may be an appropriate method to induce persistent seizures.Moreover,MK-801 and resveratrol showed strong anti-epileptic effects;thus,both of them may be clinically valuable treatments for epilepsy.

N-methyl-D-aspartic acid receptor 1 （NMDAR1） aggravates secondary inflammatory damage induced by hemin-NLRP3 pathway after intracerebral hemorrhage

Objective： Inflammation plays a critical role in secondary brain damage after intracerebral hemorrhage （ICH）. However, the mechanisms of inflammatory injury following ICH are still unclear, particularly the involvement of NLRP3 inflammasome, which are crucial to sterile inflammatory responses. In this study, we aim to test the hypothesis that NLRP3 signaling pathway takes a vital position in ICH-induced sec- ondary inflammatory damage and detect the role of N-methyl-D-aspartic acid receptor 1 （NMDARI） in this progress. Methods： ICH was induced in mice by microinjection of heroin into the striatum. The protein levels of NMDAR1, NMDAR1 phosphorylation, NLRP3 and IL-113 were measured by Western blot. The binding of NMDARI to NLRP3 was detected by immunoprecipitation. Results： The expression of NMDARI, NMDAR1 phosphorylation, NLRP3 and IL-I ~ were rapidly increased after ICH. Heroin treatment enhanced NMDAR1 expression and NMDAR1 phosphorylation, as well in cultured microglial cells treated by hemin. Hemin up-regulated NLRP3 and IL-I]3 level, which was reversed by MK801 （NMDAR antagonist） in vitro. Hemin also promoted the binding of NMDAR1 to NLRP3. Conclusion： Our findings suggest that NMDARI plays a pivotal role in hemin-induced NLRP3-mediated inflammatory damage through synergistic activation.

Tongluo Huatan capsule(通络化痰胶囊) improves cognitive function by regulating the endocytosis of N-methyl-D-aspartic acid receptors mediated by clathrin in a rat model of vascular dementia

OBJECTIVE:To explore the neuroprotective mechanisms of Tongluo Huatan capsule(THC)in a rat model of vascular dementia(VD).METHODS:A rat model of VD was established by repeated clamping of bilateral common carotid arteries with the intraperitoneal injection of sodium nitroprusside solution.VD rats were administered THC,memantine hydrochloride,or distilled water daily for 14 d after operation.Learning and memory abilities were assessed using the step-down passive avoidance test,novel object recognition(NOR)test,and Morris water maze(MWM)test.Pathological changes in the hippocampus were observed through hematoxylin and eosin and Nissl staining.The expression levels of clathrin,RAB5 B,andN-methyl-D-aspartic acid receptor 1(NMDAR1)were measured by immunohistochemistry staining,real-time quantitative polymerase chain reaction and Western blot.RESULTS:Rats in VD group showed impaired learning and memory abilities(step-down passive avoidance,NOR,and MWM)and abnormalities in neuronal morphology(light microscopy)in the hippocampus.The m RNA or protein expression levels of clathrin and RAB5 B were decreased,and NMDAR1 was increased in hippocampal tissues(P<0.05).Administration of THC promoted the learning and memory abilities and the morphological structure of hippocampal neurons in VD rats.Besides,THC enhanced m RNA or protein expression levels of clathrin and RAB5 B,and decreased NMDAR1(P<0.05).CONCLUSION:THC may improve cognitive functions by regulating the endocytosis of NMDA receptors mediated by clathrin.

STAT3 ameliorates truncated tau-induced cognitive deficits

Proteolytic cleavage of tau by asparagine endopeptidase(AEP)creates tau-N368 fragments,which may drive the pathophysiology associated with synaptic dysfunction and memory deterioration in the brain of Alzheimer’s disease patients.Nonetheless,the molecular mechanisms of truncated tau-induced cognitive deficits remain unclear.Evidence suggests that signal transduction and activator of transcription-3(STAT3)is associated with modulating synaptic plasticity,cell apoptosis,and cognitive function.Using luciferase reporter assays,electrophoretic mobility shift assays,western blotting,and immunofluorescence,we found that human tau-N368 accumulation inhibited STAT3 activity by suppressing STAT3 translocation into the nucleus.Overexpression of STAT3 improved tau-N368-induced synaptic deficits and reduced neuronal loss,thereby improving the cognitive deficits in tau-N368 mice.Moreover,in tau-N368 mice,activation of STAT3 increased N-methyl-D-aspartic acid receptor levels,decreased Bcl-2 levels,reversed synaptic damage and neuronal loss,and thereby alleviated cognitive deficits caused by tau-N368.Taken together,STAT3 plays a critical role in truncated tau-related neuropathological changes.This indicates a new mechanism behind the effect of tau-N368 on synapses and memory deficits.STAT3 can be used as a new molecular target to treat tau-N368-induced protein pathology.

In silico insight into Amurensinine - an N-Methyl-D-Aspartate receptor antagonist

BACKGROUND Some isopavines can exhibit important biological activity in the treatment of neurological disorders since it is considered an antagonist of the specific Nmethyl-D-Aspartate(NMDA)receptor.Amurensinine is an isopavine which still has few studies.In view of the potential of isopavines as NMDA receptor antagonists,theoretical studies using bioinformatics were carried out in order to investigate whether Amurensinine binds to the NMDA receptor and to analyze the receptor/Ligand complex.This data can contribute to understanding of the onset of neurological diseases and contribute to the planning of drugs for the treatment of neurological diseases involving the NMDA receptor.AIM To investigate the interaction of the antagonist Amurensinine on the GluN1A/GluN2B isoform of the NMDA receptor using bioinformatics.METHODS The three-dimen-sional structure of the GluN1A/GluN2B NMDA receptor was selected from the Protein Data Bank(PDB)-PDB:4PE5,and the three-dimensional structure of Amurensinine(ligand)was designed and optimized using ACD/SchemsketchTM software.Prediction of the protonation state of Amurensinine at physiological pH was performed using MarvinSketch software(ChemAxon).Protonated and non-protonated Amurensin were prepared using AutoDock Tools 4 software and simulations were performed using Autodock Vina v.1.2.0.The receptor/Ligand complexes were analyzed using PyMol(Schrödinger,Inc)and BIOVIA Discovery Studio(Dassault Systemes)software.To evaluate the NMDA receptor/Amurensinine complex and validate the molecular docking,simulations using NMDA receptor and Ifenprodil antagonist were performed under the same conditions.Ifenprodil was also designed,optimized and protonated,under the same conditions as Amurensinine.RESULTS Molecular docking simulations showed that both non-protonated and protonated Amurensinine bind to the amino terminal domain(ATD)domain of the GluN1A/GluN2B NMDA receptor with significant affinity energy,-7.9 Kcal/mol and-8.1 Kcal/mol,respectively.The NMDA receptor/non-protonated Amurensinine complex was stabilized by 15 bonds,while the NMDA receptor/protonated Amurensinine complex was stabilized by less than half,6 bonds.Despite the difference in the number of bonds,the variation in bond length and the average bond length values are similar in both complexes.The complex formed by the NMDA receptor and Ifenprodil showed an affinity energy of-8.2 Kcal/mol,a value very close to that obtained for the NMDA receptor/Amurensinine complex.Molecular docking between Ifenprodil and the GluN1A/GluN2B NMDA receptor demonstrated that this antagonist interacts with the ATD of the receptor,which validates the simulations performed with Amurensinine.CONCLUSION Amurensinine binds to the NMDA receptor on ATD,similar to Ifenprodil,and the affinity energy is closer.These data suggest that Amurensinine could behave as a receptor inhibitor,indicating that this compound may have a potential biological application,which should be evaluated by in vitro and preclinical assays.

Neuroprotective effects of Shaoyao Gancao decoction against excitatory damage in PC12 cells based on the Src-NR2-nNOS pathway

Objective:To explore the neuroprotective effects of the Shaoyao Gancao decoction(SGD)against excitatory damage in PC12 cells and the role of the Src-NR2-nNOS pathway mediation by SGD in regulatingγ-aminobutyric acid(GABA)-glutamate(Glu)homeostasis.Methods: N-Methyl-d-aspartic acid(NMDA)was used to establish a PC12 cell excitability injury model.To investigate the neuroprotective effect of SGD,a cell counting kit-8(CCK-8)assay was used to determine PC12 cell viability,Annexin V/Propidium Iodide(Annexin V/PI)double staining was used to determine PC12 cell apoptosis,and Ca^(2+)concentration was observed using laser confocal microscopy.GABA receptor agonists and antagonists were used to analyze the neuroprotective interactions betweenγ-aminobutyric acid(GABA)and NMDA receptors.Additionally,molecular biology techniques were used to determine mRNA and protein expression in the Src-NR2-nNOS pathway.We analyzed the correlations between the regulatory sites of GABA and NMDA interactions,excitatory neurotoxicity,and brain damage at the molecular level.Results: NMDA excitotoxic injury manifested as a significant decrease in cell activity,increased apoptosis and caspase-3 protein expression,and a significant increase in intracellular Ca^(2+)concentration.Administration of SGD,a GABAA receptor agonist(muscimol),or a GABAB receptor agonist(baclofen)decreased intracellular Ca^(2+)concentrations,attenuated apoptosis,and reversed NMDA-induced upregulation of caspase-3,Src,NMDAR2A,NMDAR2B,and nNOS.Unexpectedly,a GABA_(A)receptor antagonist(bicuculline)and a GABA_(B)receptor antagonist(saclofen)failed to significantly increase excitatory neurotoxicity.Conclusions: Taken together,these results not only provide an experimental basis for SGD administration in the clinical treatment of central nervous system injury diseases,but also suggest that the Src-NR2A-nNOS pathway may be a valuable target in excitotoxicity treatment.

Sorl1 knockout inhibits expression of brain-derived neurotrophic factor:involvement in the development of late-onset Alzheimer's disease

Sortilin-related receptor 1(SORL1)is a critical gene associated with late-onset Alzheimer’s disease.SORL1 contributes to the development and progression of this neurodegenerative condition by affecting the transport and metabolism of intracellularβ-amyloid precursor protein.To better understand the underlying mechanisms of SORL1 in the pathogenesis of late-onset Alzheimer s disease,in this study,we established a mouse model of SorI1 gene knockout using cluste red regularly inters paced short palindro mic repeats-associated protein 9 technology.We found that Sorl1-knocko ut mice displayed deficits in learning and memory.Furthermore,the expression of brain-derived neurotrophic factor was significantly downregulated in the hippocampus and co rtex,and amyloidβ-protein deposits were observed in the brains of 5orl1-knockout mice.In vitro,hippocampal neuronal cell synapses from homozygous Sorl1-knockout mice were impaired.The expression of synaptic proteins,including Drebrin and NR2B,was significantly reduced,and also their colocalization.Additionally,by knocking out the Sorl1 gene in N2a cells,we found that expression of the N-methyl-D-aspartate receptor,NR2B,and cyclic adenosine monophosphate-response element binding protein was also inhibited.These findings suggest that SORL1 participates in the pathogenesis of late-onset Alzheimer s disease by regulating the N-methyl-D-aspartate receptor NR2B/cyclic adenosine monophosphate-response element binding protein signaling axis.

General anesthetic agents induce neurotoxicity through astrocytes

Neuroscientists have recognized the importance of astrocytes in regulating neurological function and their influence on the release of glial transmitters.Few studies,however,have focused on the effects of general anesthetic agents on neuroglia or astrocytes.Astrocytes can also be an important target of general anesthetic agents as they exert not only sedative,analgesic,and amnesic effects but also mediate general anesthetic-induced neurotoxicity and postoperative cognitive dysfunction.Here,we analyzed recent advances in understanding the mechanism of general anesthetic agents on astrocytes,and found that exposure to general anesthetic agents will destroy the morphology and proliferation of astrocytes,in addition to acting on the receptors on their surface,which not only affect Ca^(2+)signaling,inhibit the release of brain-derived neurotrophic factor and lactate from astrocytes,but are even involved in the regulation of the pro-and anti-inflammatory processes of astrocytes.These would obviously affect the communication between astrocytes as well as between astrocytes and neighboring neurons,other neuroglia,and vascular cells.In this review,we summarize how general anesthetic agents act on neurons via astrocytes,and explore potential mechanisms of action of general anesthetic agents on the nervous system.We hope that this review will provide a new direction for mitigating the neurotoxicity of general anesthetic agents.

Acute and chronic excitotoxicity in ischemic stroke and late-onset Alzheimer's disease

Stroke and Alzheimer's disease are common neurological disorders and often occur in the same individuals.The comorbidity of the two neurological disorders represents a grave health threat to older populations.This review presents a brief background of the development of novel concepts and their clinical potentials.The activity of glutamatergic N-methyl-D-aspartate receptors and N-methyl-D-aspartate receptor-mediated Ca^(2+)influx is critical for neuronal function.An ischemic insult induces prompt and excessive glutamate release and drastic increases of intracellular Ca^(2+)mainly via N-methyl-D-aspartate receptors,particularly of those at the extrasynaptic site.This Ca^(2+)-evoked neuronal cell death in the ischemic core is dominated by necrosis within a few hours and days known as acute excitotoxicity.Furthermore,mild but sustained Ca^(2+)increases under neurodegenerative conditions such as in the distant penumbra of the ischemic brain and early stages of Alzheimer's disease are not immediately toxic,but gradually set off deteriorating Ca^(2+)-dependent signals and neuronal cell loss mostly because of activation of programmed cell death pathways.Based on the Ca^(2+)hypothesis of Alzheimer's disease and recent advances,this Ca^(2+)-activated“silent”degenerative excitotoxicity evolves from years to decades and is recognized as a unique slow and chronic neuropathogenesis.The N-methyl-D-aspartate receptor subunit GluN3A,primarily at the extrasynaptic site,serves as a gatekeeper for the N-methyl-D-aspartate receptor activity and is neuroprotective against both acute and chronic excitotoxicity.Ischemic stroke and Alzheimer's disease,therefore,share an N-methyl-D-aspartate receptor-and Ca^(2+)-mediated mechanism,although with much different time courses.It is thus proposed that early interventions to control Ca^(2+)homeostasis at the preclinical stage are pivotal for individuals who are susceptible to sporadic late-onset Alzheimer's disease and Alzheimer's disease-related dementia.This early treatment simultaneously serves as a preconditioning therapy against ischemic stroke that often attacks the same individuals during abnormal aging.

Targeting harmful effects of non-excitatory amino acids as an alternative therapeutic strategy to reduce ischemic damage

The involvement of the excitatory amino acids glutamate and aspartate in ce rebral ischemia and excitotoxicity is well-documented.Nevertheless,the role of non-excitatory amino acids in brain damage following a stroke or brain trauma remains largely understudied.The release of amino acids by necrotic cells in the ischemic core may contribute to the expansion of the penumbra.Our findings indicated that the reversible loss of field excitato ry postsynaptic potentials caused by transient hypoxia became irreversible when exposed to a mixture of just four non-excitatory amino acids(L-alanine,glycine,L-glutamine,and L-serine)at their plasma concentrations.These amino acids induce swelling in the somas of neurons and astrocytes during hypoxia,along with permanent dendritic damage mediated by N-methyl-D-aspartate receptors.Blocking N-methyl-D-aspartate receptors prevented neuronal damage in the presence of these amino acids during hypoxia.It is likely that astroglial swelling caused by the accumulation of these amino acids via the alanine-serine-cysteine transporter 2 exchanger and system N transporters activates volume-regulated anion channels,leading to the release of excitotoxins and subsequent neuronal damage through N-methyl-D-aspartate receptor activation.Thus,previously unrecognized mechanisms involving non-excitatory amino acids may contribute to the progression and expansion of brain injury in neurological emergencies such as stroke and traumatic brain injury.Understanding these pathways co uld highlight new therapeutic targets to mitigate brain injury.

Inhibition of N-methyl-D-aspartate-activated Current by Bis(7)-tacrine in HEK-293 Cells Expressing NR1/NR2A or NR1/NR2B Receptors

In normal rat forebrain, the NR1/NR2A and NR1/NR2B dimmers are the main constitutional forms of NMDA receptors. The present study was carried out to determine the functional properties of the heteromeric NMDA receptor subunits and their inhibition by bis(7)-tacrine (B7T). Rat NR1, NR2A and NR2B cDNAs were transfected into human embryonic kidney 293 cells (HEK-293).The inhibition of NMDA-activated currents by B7T was detected in HEK-293 cell expressing NR1/NR2A or NR1/NR2B receptors by using whole-cell patch-clamp techniques. The results showed that in HEK-293 cells expressing NR1/NR2A receptor, 1μmol/L B7T inhibited 30μmol/L NMDA- and 1000μmol/L NMDA-activated steady-state currents by 46% and 40%, respectively (P>0.05; n=5), suggesting that the inhibition of B7T on NR1/NR2A receptor doesn’t depend on NMDA concentration, which is consistent with a non-competitive mechanism of inhibition. But for the NR1/NR2B receptor, 1μmol/L B7T inhibited 30μmol/L NMDA- and 1000 μmol/L NMDA-activated steady-state currents by 61% and 13%, re-spectively (P<0.05; n=6), showing that B7T appears to be competitive with NMDA. In addition, simultaneous application of 1μmol/L B7T and 1000μmol/L NMDA produced a moderate inhibition of peak NMDA-activated current, followed by a gradual decline of the current to a steady state. However, the gradual onset of inhibition produced by B7T applied simultaneously with NMDA was eliminated when B7T was given 5s before NMDA. These results suggested that B7T inhibition of NMDA current mediated by NR1/NR2B receptor was slow onset, and it did not depend on the presence of the agonist. With holding potentials ranging from -50 to +50 mV, the B7T inhibition rate of NMDA currents didn’t change significantly, and neither did the reversal potential. We are led to conclude that the NR1/NR2B recombinant receptor can serve as a very useful model for studying the molecular mechanism of NMDA receptor inhibition by B7T.

N-methyl-D-aspartate receptor subunit 1 regulates neurogenesis in the hippocampal dentate gyrus of schizophrenia-like mice

N-methyl-D-aspartate receptor hypofunction is the basis of pathophysiology in schizophrenia. Blocking the N-methyl-D-aspartate receptor impairs learning and memory abilities and induces pathological changes in the brain. Previous studies have paid little attention to the role of the N-methyl-D-aspartate receptor subunit 1 (NR1) in neurogenesis in the hippocampus of schizophrenia. A mouse model of schizophrenia was established by intraperitoneal injection of 0.6 mg/kg MK-801, once a day, for 14 days. In N-methyl-D-aspartate-treated mice, N-methyl-D-aspartate was administered by intracerebroventricular injection in schizophrenia mice on day 15. The number of NR1-, Ki67- or BrdU-immunoreactive cells in the dentate gyrus was measured by immunofluorescence staining. Our data showed the number of NR1-immunoreactive cells increased along with the decreasing numbers of BrdU- and Ki67-immunoreactive cells in the schizophrenia groups compared with the control group. N-methyl-D-aspartate could reverse the above changes. These results indicated that NR1 can regulate neurogenesis in the hippocampal dentate gyrus of schizophrenia mice, supporting NR1 as a promising therapeutic target in the treatment of schizophrenia. This study was approved by the Experimental Animal Ethics Committee of the Ningxia Medical University, China (approval No. 2014-014) on March 6, 2014.

Propofol effectively inhibits lithium-pilocarpine-induced status epilepticus in rats via downregulation of N-methyl-D-aspartate receptor 2B subunit expression

Status epilepticus was induced via intraperitoneal injection of lithium-pilocarpine.The inhibitory effects of propofol on status epilepticus in rats were judged based on observation of behavior,electroencephalography and 24-hour survival rate.Propofol（12.5-100 mg/kg） improved status epilepticus in a dose-dependent manner,and significantly reduced the number of deaths within 24 hours of lithium-pilocarpine injection.Western blot results showed that,24 hours after induction of status epilepticus,the levels of N-methyl-D-aspartate receptor 2A and 2B subunits were significantly increased in rat cerebral cortex and hippocampus.Propofol at 50 mg/kg significantly suppressed the increase in N-methyl-D-aspartate receptor 2B subunit levels,but not the increase in N-methyl-D-aspartate receptor 2A subunit levels.The results suggest that propofol can effectively inhibit status epilepticus induced by lithium-pilocarpine.This effect may be associated with downregulation of N-methyl-D-aspartate receptor 2B subunit expression after seizures.

Influences of levodopa on expression of N-methyl-D-aspartate receptor-1-subunit in the visual cortex of monocular deprivation rats

AIM: Many studies have demonstrated N-methyl-D-aspartate receptor-1-subunit (NMDAR1) is associated with amblyopia. The effectiveness of levodopa in improving the visual function of the children with amblyopia has also been proved. But the mechanism is undefined. Our study was to explore the possible mechanism. METHODS: Sixty 14-day-old healthy SD rats were randomly divided into 4 groups, including normal group, monocular deprivation group, levodopa group and normal saline group, 15 rats each. We sutured all the rats' unilateral eyelids except normal group to establish the monocular deprivation animal model and raise them in normal sunlight till 45-day-old. NMDAR1 was detected in the visual cortex with immunohistochemistry methods, Western Blot and Real time PCR. LD and NS groups were gavaged with levodopa (40mg/kg) and normal saline for 28 days respectively. NMDAR1 was also detected with the methods above. RESULTS: NMDAR1 in the visual cortex of MD group was less than that of normal group. NMDAR1 in the visual cortex of LD group was more than that of NS group. CONCLUSION: NMDAR1 is associated with the plasticity of visual development. Levodopa may influence the expression of NMDAR1 and improve visual function, and its target may lie in the visual cortex.

Changes in synaptic and extrasynaptic N-methyl-D-aspartate receptor-mediated currents at early-stage epileptogenesis in adult mice

Previous reports have shown that N-methyl-D-aspartate （NMDA） receptors are extensively involved in epilepsy genesis and recurrence. Recent studies have shown that synaptic and extrasynaptic NMDA receptors play different, or even opposing, roles in various signaling pathways, including synaptic plasticity and neuronal death. The present study analyzed changes in synaptic and extrasynaptic NMDA receptor-mediated currents during epilepsy onset. Mouse models of lithium chloride pilocarpLne-induced epilepsy were established, and hippocampal slices were prepared at 24 hours after the onset of status epilepticus. Synaptic and extrasynaptic NMDA receptor-mediated excitatory post-synaptic currents （NMDA-EPSCs） were recorded in CA1 pyramidal neurons by whole-cell patch clamp technique. Results demonstrated no significant difference in rise and delay time of synaptic NMDA-EPSCs compared with normal neurons. Peak amplitude, area-to-peak ratio, and rising time of extrasynaptic NMDA-EPSCs remained unchanged, but decay of extrasynaptic NMDA-EPSCs was faster than that of normal neurons, These results suggest that extrasynaptic NMDA receptors play a role in epileptogenesis.

N-methyl-D-aspartate receptor subtype 3A promotes apoptosis in developing mouse brain exposed to hyperoxia

In the present study, 7 day postnatal C57/BL6 wild-type mice （hyperoxia group） and 7 day postnatal N-methyI-D-aspartate receptor subtype 3A knockout mice （NR3A KO group） were exposed to 75% oxygen and 15% nitrogen in a closed container for 5 days. Wild-type mice raised in normoxia served as controls. TdT-mediated dUTP nick end labeling （TUNEL）/neuron-specific nuclear protein （NeuN） and 5-bromo-2＇-deoxyuridine （BrdU）/NeuN immunofluorescence staining showed that the number of apoptotic cells and the number of proliferative cells in the dentate subgranular zone significantly increased in the hyperoxia group compared with the control group. However, in the same hyperoxia environment, the number of apoptotic cells and the number of proliferative cells significantly decreased in the NR3A KO group compared with hyperoxia group. TUNEL＋/NeuN＋ and BrdU＋/NeuN~ cells were observed in the NR3A KO and the hyperoxia groups. These results demonstrated that the NR3A gene can promote cell apoptosis and mediate the potential damage in the developing brain induced by exposure to non-physiologically high concentrations of oxygen.

Dose-dependent and combined effects of N-methyl-D-aspartate receptor antagonist MK-801 and nitric oxide synthase inhibitor nitro-L-arginine on the survival of retinal ganglion cells in adult hamsters

This study investigated the effects of daily intraperitoneal injections of N-methyl-D-aspartate receptor antagonist MK-801 and nitric oxide synthase inhibitor nitro-L-arginine （L-NA） on the survival of retinal ganglion cells （RGCs） at 1 and 2 weeks after unilateral optic nerve transection in adult hamsters. The left optic nerves of all animals were transected intraorbitally 1 mm from the optic disc and RGCs were retrogradely labeled with Fluorogold before they received different daily dosages of single MK-801 or L-NA as well as daily combinational treatments of these two chemicals. All experimental and control animals survived for 1 or 2 weeks after optic nerve transection. Our results revealed that the mean numbers of surviving RGCs increased and then decreased when the dosage of MK-801 （1.0, 3.0 and 4.5 mg/kg） and L-NA （1.5, 3.0, 4.5 and 6.0 mg/kg） increased at both 1 and 2 weeks survival time points. Daily combinational use of 1.0 mg/kg MK-801 and 1.5 mg/kg L-NA lead to a highest RGC number that was even higher than the sum of the RGC numbers in 1.0 mg/kg MK-801 and 1.5 mg/kg L-NA subgroups at 2 weeks. These findings indicated that both MK-801 and L-NA can protect axotomized RGCs in a dose-dependent manner and combinational treatment of these chemicals possesses a potentiative and protective effect.

Kappa opioid receptor antagonist and N-methyl-D-aspartate receptor antagonist affect dynorphin-induced spinal cord electrophysiologic impairment

The latencies of motor- and somatosensory-evoked potentials were prolonged to different degrees, and wave amplitude was obviously decreased, after injection of dynorphin into the rat subarachnoid cavity. The wave amplitude and latencies of motor- and somatosensory-evoked potentials were significantly recovered at 7 and 14 days after combined injection of dynorphin and either the kappa opioid receptor antagonist nor-binaltorphimine or the N-methyl-D-aspartate receptor antagonist MK-801. The wave amplitude and latency were similar in rats after combined injection of dynorphin and nor-binaltorphimine or MK-801. These results suggest that intrathecal injection of dynorphin causes damage to spinal cord function. Prevention of N-methyl-D-aspartate receptor or kappa receptor activation lessened the injury to spinal cord function induced by dynorphin.