NMDA Receptor Antagonist MK801 Protects Against 1-Bromopropane-Induced Cognitive Dysfunction / 神经科学通报·英文版

Occupational exposure to 1-bromopropane (1-BP) induces learning and memory deficits. However, no therapeutic strategies are currently available. Accumulating evidence has suggested that N-methyl-D-aspartate receptors (NMDARs) and neuroinflammation are involved in the cognitive impairments in neurodegenerative diseases. In this study we aimed to investigate whether the noncompetitive NMDAR antagonist MK801 protects against 1-BP-induced cognitive dysfunction. Male Wistar rats were administered with MK801 (0.1 mg/kg) prior to 1-BP intoxication (800 mg/kg). Their cognitive performance was evaluated by the Morris water maze test. The brains of rats were dissected for biochemical, neuropathological, and immunological analyses. We found that the spatial learning and memory were significantly impaired in the 1-BP group, and this was associated with neurodegeneration in both the hippocampus (especially CA1 and CA3) and cortex. Besides, the protein levels of phosphorylated NMDARs were increased after 1-BP exposure. MK801 ameliorated the 1-BP-induced cognitive impairments and degeneration of neurons in the hippocampus and cortex. Mechanistically, MK801 abrogated the 1-BP-induced disruption of excitatory and inhibitory amino-acid balance and NMDAR abnormalities. Subsequently, MK801 inhibited the microglial activation and release of pro-inflammatory cytokines in 1-BP-treated rats. Our findings, for the first time, revealed that MK801 protected against 1-BP-induced cognitive dysfunction by ameliorating NMDAR function and blocking microglial activation, which might provide a potential target for the treatment of 1-BP poisoning.

Recapitulation of Neuropsychiatric Behavioral Features in Mice Using Acute Low-dose MK-801 Administration

Despite some innate limitations, animal models are a potent investigative tool when used to model specific symptoms of a disorder. For example, MK-801, an N-methyl-D-aspartate receptor antagonist, is used as a pharmacological tool to induce symptoms found in some neuropsychiatric disorders. However, a close examination of literature suggests that the application window of MK-801 doses is relatively narrow between individual behavioral paradigms, necessitating careful characterization of the evoked behavioral aberrations and the doses used to induce them. Moreover, variation in behaviors depending on the animal strain, gender of the subject, and the timing of administration is observed, making it difficult to compare the behavioral characteristics reported in different studies. We aim to characterize the behavioral aberrations induced by different doses of MK-801 in CD-1 mice and create a ready reference for future studies. We used CD-1 mice to recapitulate behavioral impairments resulting from acute administration of MK-801. In 0.1 mg kg⁻¹, we observed diminished spontaneous alteration during the Y-maze test, while 0.12 mg kg⁻¹ resulted in hyperlocomotion and social deficit. Mice treated with 0.2 and 0.3 mg kg⁻¹ of MK-801 demonstrated a decreased self-grooming. Finally, all doses significantly impaired cliff avoidance behaviors suggesting increased impulsivity. These results affirm that MK-801 can effectively model various symptoms of different neuropsychiatric disorders in a dose-dependent manner. The observed sensitivity against spatial-memory impairment and impulsive behaviors at low concentration of MK-801 suggest that MK801 may modulate cognitive function and impulsivity in even lower concentration before it can modulate other behavioral domains.

Dynamic visual analysis of neutrophils chemotaxis in peritoneal cavity of schizophrenic model in mice / 北京大学学报(医学版)

OBJECTIVE@#To compare the differences of neutrophils chemotaxis ability in peritoneal cavity between normal rats and schizopherenic rats with cell dynamic visualization system.@*METHODS@#In the study,18 healthy Kunming rats were randomly divided into 3 groups which were control group (n=6), 0.3 mg/kg MK-801 treatment group (n=6), 0.6 mg/kg dizocilpine maleate (MK-801) treatment group(n=6), extracted neutrophils separately, and observed the morphology and counted under a microscope. Each group of cells was divided into two parts for chemotactic experiment, called chemokine agent treatment group and no chemokine agent treatment group respectively, indicating control 1, 0.3 mg/kg MK-801 treatment 1,0.6 mg/kg MK-801 treatment 1 and control 2, 0.3 mg/kg MK-801 treatment 2,0.6 mg/kg MK-801 treatment 2. The dynamic migration of cells was recorded using the NIS-Elements software, and TAXIScan Analyzer 2 software was used to select 30 cells (n=30) in each group of cells and analyze cells migration trajectory, speed and distance, and use pair test and One-Way analysis of variance for statistical analysis.@*RESULTS@#The number of neutrophils in control group, 0.3 mg/kg MK-801 treatment group and 0.6 mg/kg MK-801 treatment group were(1.00±0.03)×104/mL,(0.05±0.02)×104/mL,(0.32±0.01)×104/mL respectively, the differences of results were statistically significant(P<0.05).Under the effect of chemotactic agent,the directional migration capability of neutrophils in control group 1, 0.3 mg/kg MK-801 treatment group 1 and 0.6 mg/kg MK-801 treatment group 1 were(0.85±0.11) radian,(1.00±0.11) radian,(0.96±0.10) radian respectively (P<0.05); the migration velocities of neutrophils were (0.09±0.02) μm/s,(0.12±0.01) μm/s,(0.14±0.01) μm/s respectively (P<0.05);the migration distances of neutrophils were (94.26±0.02) μm,(134.61±0.01) μm,(156.19±0.01) μm respectively(P<0.05).@*CONCLUSION@#Compared with neutrophils in peritoneal cavity of control group, the neutrophils in peritoneal cavity of schizophrenic rats have stronger chemotactic movement ability.

Dehydroevodiamine·HCl enhances cognitive function in memory-impaired rat models

Progressive memory impairment such as that associated with depression, stroke, and Alzheimer's disease (AD) can interfere with daily life. In particular, AD, which is a progressive neurodegenerative disorder, prominently features a memory and learning impairment that is related to changes in acetylcholine and abnormal β-amyloid (Aβ) deposition in the brain. In the present study, we investigated the effects of dehydroevodiamine·HCl (DHED) on cognitive improvement and the related mechanism in memory-impaired rat models, namely, a scopolamine-induced amnesia model and a Aβ₁₋₄₂-infused model. The cognitive effects of DHED were measured using a water maze test and a passive avoidance test in the memory-impaired rat models. The results demonstrate that DHED (10 mg/kg, p.o.) and Donepezil (1 mg/kg, p.o.) ameliorated the spatial memory impairment in the scopolamine-induced amnestic rats. Moreover, DHED significantly improved learning and memory in the Aβ₁₋₄₂-infused rat model. Furthermore, the mechanism of these behavioral effects of DHED was investigated using a cell viability assay, reactive oxygen species (ROS) measurement, and intracellular calcium measurement in primary cortical neurons. DHED reduced neurotoxicity and the production of Aβ-induced ROS in primary cortical neurons. In addition, similar to the effect of MK801, DHED decreased intracellular calcium levels in primary cortical neurons. Our results suggest that DHED has strong protective effects against cognitive impairments through its antioxidant activity and inhibition of neurotoxicity and intracellular calcium. Thus, DHED may be an important therapeutic agent for memory-impaired symptoms.

Dual control of the vestibulosympathetic reflex following hypotension in rats

Orthostatic hypotension (OH) is associated with symptoms including headache, dizziness, and syncope. The incidence of OH increases with age. Attenuation of the vestibulosympathetic reflex (VSR) is also associated with an increased incidence of OH. In order to understand the pathophysiology of OH, we investigated the physiological characteristics of the VSR in the disorder. We applied sodium nitroprusside (SNP) to conscious rats with sinoaortic denervation in order to induce hypotension. Expression of pERK in the intermediolateral cell column (IMC) of the T4~7 thoracic spinal regions, blood epinephrine levels, and blood pressure were evaluated following the administration of glutamate and/or SNP. SNP-induced hypotension led to increased pERK expression in the medial vestibular nucleus (MVN), rostral ventrolateral medullary nucleus (RVLM) and the IMC, as well as increased blood epinephrine levels. We co-administered either a glutamate receptor agonist or a glutamate receptor antagonist to the MVN or the RVLM. The administration of the glutamate receptor agonists, AMPA or NMDA, to the MVN or RVLM led to elevated blood pressure, increased pERK expression in the IMC, and increased blood epinephrine levels. Administration of the glutamate receptor antagonists, CNQX or MK801, to the MVN or RVLM attenuated the increased pERK expression and blood epinephrine levels caused by SNP-induced hypotension. These results suggest that two components of the pathway which maintains blood pressure are involved in the VSR induced by SNP. These are the neurogenic control of blood pressure via the RVLM and the humoral control of blood pressure via epinephrine release from the adrenal medulla.

Biflorin Ameliorates Memory Impairments Induced by Cholinergic Blockade in Mice

To examine the effect of biflorin, a component of Syzygium aromaticum, on memory deficit, we introduced a scopolamine-induced cognitive deficit mouse model. A single administration of biflorin increased latency time in the passive avoidance task, ameliorated alternation behavior in the Y-maze, and increased exploration time in the Morris water maze task, indicating the improvement of cognitive behaviors against cholinergic dysfunction. The biflorin-induced reverse of latency in the scopolamine-treated group was attenuated by MK-801, an NMDA receptor antagonist. Biflorin also enhanced cognitive function in a naïve mouse model. To understand the mechanism of biflorin for memory amelioration, we performed Western blot. Biflorin increased the activation of protein kinase C-ζ and its downstream signaling molecules in the hippocampus. These results suggest that biflorin ameliorates drug-induced memory impairment by modulation of protein kinase C-ζ signaling in mice, implying that biflorin could function as a possible therapeutic agent for the treatment of cognitive problems.

Preventive effects of imperatorin on perfluorohexanesulfonate-induced neuronal apoptosis via inhibition of intracellular calcium-mediated ERK pathway

Early life neuronal exposure to environmental toxicants has been suggested to be an important etiology of neurodegenerative disease development. Perfluorohexanesulfonate (PFHxS), one of the major perfluoroalkyl compounds, is widely distributed environmental contaminants. We have reported that PFHxS induces neuronal apoptosis via ERK-mediated pathway. Imperatorin is a furanocoumarin found in various edible plants and has a wide range of pharmacological effects including neuroprotection. In this study, the effects of imperatorin on PFHxS-induced neuronal apoptosis and the underlying mechanisms are examined using cerebellar granule cells (CGC). CGC were isolated from seven-day old rats and were grown in culture for seven days. Caspase-3 activity and TUNEL staining were used to determine neuronal apoptosis. PFHxS-induced apoptosis of CGC was significantly reduced by imperatorin and PD98059, an ERK pathway inhibitor. PFHxS induced a persistent increase in intracellular calcium, which was significantly blocked by imperatorin, NMDA receptor antagonist, MK801 and the L-type voltage-dependent calcium channel blockers, diltiazem and nifedipine. The activation of caspase-3 by PFHxS was also inhibited by MK801, diltiazem and nifedipine. PFHxS-increased ERK activation was inhibited by imperatorin, MK801, diltiazem and nifedipine. Taken together, imperatorin protects CGC against PFHxS-induced apoptosis via inhibition of NMDA receptor/intracellular calcium-mediated ERK pathway.

Differential Effects of Olanzapine and Haloperidol on MK-801-induced Memory Impairment in Mice

OBJECTIVE: We investigated the differential effects of the antipsychotic drugs olanzapine and haloperidol on MK-801-induced memory impairment and neurogenesis in mice. METHODS: MK-801 (0.1 mg/kg) was administered 20 minutes prior to behavioral testing over 9 days. Beginning on the sixth day of MK-801 treatment, either olanzapine (0.05 mg/kg) or haloperidol (0.05 mg/kg) was administered 40 minutes prior to MK-801 for the final 4 days. Spatial memory performance was measured using a Morris water maze (MWM) test for 9 days (four trials/day). Immunohistochemistry with bromodeoxyuridine (BrdU) was used to identify newborn cells labeled in tissue sections from the dentate gyrus of the hippocampus. RESULTS: MK-801 administration over 9 days significantly impaired memory performance in the MWM test compared to untreated controls (p<0.05) and these deficits were blocked by treatment with olanzapine (p<0.05) but not haloperidol. The administration of MK-801 also resulted in a decrease in the number of BrdU-labeled cells in the dentate gyrus (28.6%; p<0.01), which was prevented by treatment with olanzapine (p<0.05) but not haloperidol. CONCLUSION: These results suggest that olanzapine has a protective effect against cognitive impairments induced by MK-801 in mice via the stimulating effects of neurogenesis.

Propofol can Protect Against the Impairment of Learning-memory Induced by Electroconvulsive Shock via Tau Protein Hyperphosphorylation in Depressed Rats / 中国医学科学杂志(英文版)

<p><b>OBJECTIVE</b>To explore the possible neurophysiologic mechanisms of propofol and N-methyl-D- aspartate (NMDA) receptor antagonist against learning-memory impairment of depressed rats without olfactory bulbs.</p><p><b>METHODS</b>Models of depressed rats without olfactory bulbs were established. For the factorial design in analysis of variance, two intervention factors were included: electroconvulsive shock groups (with and without a course of electroconvulsive shock) and drug intervention groups [intraperotoneal (ip) injection of saline, NMDA receptor antagonist MK-801 and propofol. A total of 60 adult depressed rats without olfactory bulbs were randomly divided into 6 experimental groups (n=10 per group): ip injection of 5 ml saline; ip injection of 5 ml of 10 mg/kg MK-801; ip injection of 5 ml of 10 mg/kg MK-801 and a course of electroconvulsive shock; ip injection of 5 ml of 200 mg/kg propofol; ip injection of 5 ml of 200 mg/kg propofol and a course of electroconvulsive shock; and ip injection of 5 ml saline and a course of electroconvulsive shock. The learning-memory abilities of the rats was evaluated by the Morris water maze test. The content of glutamic acid in the hippocampus was detected by high-performance liquid chromatography. The expressions of p-AT8Ser202 in the hippocampus were determined by Western blot analysis.</p><p><b>RESULTS</b>Propofol, MK-801 or electroconvulsive shock alone induced learning-memory impairment in depressed rats, as proven by extended evasive latency time and shortened space probe time. Glutamic acid content in the hippocampus of depressed rats was significantly up-regulated by electroconvulsive shock and down-regulated by propofol, but MK-801 had no significant effect on glutamic acid content. Levels of phosphorylated Tau protein p-AT8Ser202 in the hippocampus was up-regulated by electroconvulsive shock but was reduced by propofol and MK-801 alone. Propofol prevented learning-memory impairment and reduced glutamic acid content and p-AT8Ser202 levels induced by electroconvulsive shock.</p><p><b>CONCLUSION</b>Electroconvulsive shock might reduce learning-memory impairment caused by protein Tau hyperphosphorylation in depressed rats by down-regulating glutamate content.</p>

The Downregulation of Somatic A-Type K+ Channels Requires the Activation of Synaptic NMDA Receptors in Young Hippocampal Neurons of Rats

The downregulation of A-type K+ channels (IA channels) accompanying enhanced somatic excitability can mediate epileptogenic conditions in mammalian central nervous system. As IA channels are dominantly targeted by dendritic and postsynaptic processings during synaptic plasticity, it is presumable that they may act as cellular linkers between synaptic responses and somatic processings under various excitable conditions. In the present study, we electrophysiologically tested if the downregulation of somatic IA channels was sensitive to synaptic activities in young hippocampal neurons. In primarily cultured hippocampal neurons (DIV 6~9), the peak of IA recorded by a whole-cell patch was significantly reduced by high KCl or exogenous glutamate treatment to enhance synaptic activities. However, the pretreatment of MK801 to block synaptic NMDA receptors abolished the glutamate-induced reduction of the IA peak, indicating the necessity of synaptic activation for the reduction of somatic IA. This was again confirmed by glycine treatment, showing a significant reduction of the somatic IA peak. Additionally, the gating property of IA channels was also sensitive to the activation of synaptic NMDA receptors, showing the hyperpolarizing shift in inactivation kinetics. These results suggest that synaptic LTP possibly potentiates somatic excitability via downregulating IA channels in expression and gating kinetics. The consequential changes of somatic excitability following the activity-dependent modulation of synaptic responses may be a series of processings for neuronal functions to determine outputs in memory mechanisms or pathogenic conditions.

Effects of Dizocilpine (MK-801) via Up-modulation of N-methyl-D-aspartate (NMDA) Receptors on Hypoxic-Ischemic Brain Injury in Neonatal Rats / 대한주산의학회잡지

OBJECTIVE: Several studies have demonstrated the neuroprotective effects of (+)-MK-801 hydrogen maleate (dizocilpine), in various animal models of hypoxic-ischemic (HI) brain injury. However limited data are available on the neonatal model of HI brain injury. The aim of the present study was to investigate the effects of dizocilpine and its mechanisms associated with NMDARs expression in neonatal rat model of HI brain injury. METHODS: In in vivo model, 7d-old rat pups underwent permanent unilateral carotid ligation. The animals were divided into six groups: N, normoxia; H, hypoxia without operation; HS, hypoxia with Sham operation; HO, hypoxia with operation; HV, HO treated with vehicle; HD, HO treated with dizocilpine. Dizocilpine (10 mg/kg) was administered intracerebrally to the rats 30 min before HI brain injury. Rat pups were exposed to hypoxia by placing them for 2 hours in hypoxic incubator (92% N2, 8% O2). In in vitro model, embryonic cortical neuronal cell cultures (from SD rats of embryonic days of 18) were done. The normoxia (N) group was prepared in 5% CO2 incubators. The hypoxia (H), and hypoxia treated with dizocilpine (HD) groups were placed in 1% O2 incubators (94% N2, 5% CO2) for 16 hours. In order to estimation of cell viability and growth, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide (MTT) assay was done. The degree of neuronal death was evaluated by morphometric method and the protein expression of each NMDARs was quantified by Real Time-PCR and Western blot. RESULTS: Both in the in vitro and in vivo models, the expressions of NMDAR subunits were lower in the hypoxia group than in the normoxia group, whereas they increased in the hypoxia treated with dizocilpine group compared to the hypoxia group. In vitro model, however, the expressions of NR1, NR2A mRNAs decreased in the H group when compared to the N group, whereas they increased a little in the HD group when compared to the H group. CONCLUSION: Dizocilpine was modulated the degeneration of neuronal cell death in neonatal rat model of HI by preservation of NR expression.

Inibição do receptor de glutamato do tipo NMDA em um modelo de hipóxia-isquemia prenatal: avaliação morfofuncional do cerebelo / Inhibition of glutamate NMDA receptor in a prenatal hipoxia-ischemia model: morphofunctional analises of cerebellum

Lesões sistêmicas peri e pré-natais alteram o desenvolvimento do SNC, levando a problemas cognitivos e motores em crianças que podem perdurar por toda a vida. Um tipo particular de lesão é a hipóxia-isquemia (HI), caracterizada pela interrupção momentânea ou permanente do fluxo sanguíneo. Um dos mecanismos propostos para as lesões decorrentes da HI é a excitotoxicidade glutamatérgica. O uso de inibidores da neurotransmissão glutamatérgica tem sido estudados em diversos modelos de HI. Neste trabalho, avaliamos os efeitos morfofuncionais da administração de um antagonista não-competitivo do receptor de glutamato NMDA sobre o desenvolvimento do cerebelo. Ratas no 18º dia de gestação foram anestesiadas, os cornos uterinos expostos e as 4 artérias uterinas obstruídas por 45 minutos (Grupo H). Animais controle tiveram os úteros expostos, sem a obstrução (Grupo S). Após a cirurgia a gestação prosseguiu. Somente animais nascidos a termo foram utilizados. Um dia após o nascimento, metade de cada ninhada foi designada para receber MK801, 0,3mg/kg/dia, (grupos SM e HM) e a outra metade recebeu solução salina (grupos SS e HS), por 5 dias. Após anestesia e perfusão-fixação com paraformaldeído 4% aos 9, 23, 30 e 60 dias pós-natais, cortes parassagitais do cerebelo foram obtidos em criótomo e submetidos à imunohistoquímica para calbindina, GFAP, GLAST, PDGFRα e MBP. A partir de 45 dias de vida, os animais foram testados em vários de testes comportamentais: labirinto em cruz elevado (LCE), campo vazado (CV), ROTAROD, teste de caminhada sobre barras (ladder test) e teste do comprimento da passada (stride length). Aos 9 dias, a espessura da árvore dendrítica era menor nos animais SM, HS/HM, demonstrando efeitos deletérios tanto do MK801 quanto da HI. Menor número de células PDGFRα+ foi observado nos animais HS/HM, sem efeitos da administração de MK801. Aos 23 dias, maior número de células PDGFRα+ foi observado nos animais HM comparado aos outros 3 grupos, indicando efeito ...

Peri and prenatal systemic lesions alter CNS development leading to motor and cognitive problems in children that might persist throughout life. A particular kind of injury, the hypoxic ischemic (HI), is characterized by a permanent or temporary blockage of blood flow. One of the proposed mechanisms downstream from a HI event is called glutamatergic excitotoxicity. The administration of glutamate inhibitors has been studied in HI models for several years. In this work, we evaluated the effects of administration of a non-competitive antagonist of glutamate receptor, NMDA, on cerebellar development and behavioral tests of HI animals. Pregnant rats in the 18th gestational day were anesthetized, the uterine horns were exposed and the four uterine arteries were clamped for 45 minutes (group H). Sham controls had the uterine horns exposed, but no arteries were clamped (group S). Gestation proceeded after surgery. Only full term animals were used. One day after birth half the animals was assigned to receive either SALINE (groups SS and HS) or MK801 (groups SM and HM). Animals were anesthetized and perfused with 4% paraformaldehyde at 9, 23, 30 and 60 days of age. Parasagittal cerebellar sections were submitted to Calbindin, GFAP, GLAST, PDGFRα and MBP immunohistochemistry. Beginning at P45 animals were subjected to a battery of behavioral tests: elevated plus maze (EPM), hole board (HB), ROTAROD, ladder test and stride length. At P9 the dendritic tree of Purkinje cells were thinner in SM, HS/HM animals, indicating that both HI and MK801 are deleterious regarding this Purkinje cell differentiation. A lower number of PDGFRα+ cells was observed in HS/HM animals, with no effects of MK801 administration. At P23 a greater number of PDGFRα+ cells was found in HM animals when compared to the other 3 groups, demonstrating a neuroprotector effect of MK801. A lower number of myelinated fibers (MBP+) was observed in HS animals at P9, and MK801 administration reverse this ...

Establishment and application of a mouse model for drug-induced schizophrenia / 药学学报

Schizophrenia, described as the worst disease affecting mankind, is a severe and disabling mental disorder. Schizophrenia is characterized by complicated symptoms and still lacks a diagnostic neuropathology, so developing schizophrenia animal models which have quantifiable measures tested in a similar fashion in both humans and animals will play a key role in new therapeutic approaches. According to the symptoms of cognitive impairment and emotional disorder, the N-methyl-d-aspartate (NMDA)-receptor antagonist MK-801 was applied to induce schizophrenia-like behavior in mice. Locomotor activity and prepulse inhibition (PPI) were selected as indices and the effect of clozapine was also investigated in this model. The results showed that compared with the normal group, MK-801-treated mice exhibited significantly increased locomotor activity and impaired PPI, and pre-exposure to clozapine could ameliorate the abnormality and make it back to normal level. These findings suggest that the model we established could be a useful tool for antipsychotic drug screening.

Hippocampus quinolinic acid modulates glutamate and NMDAR/mGluR1 in chronic unpredictable mild stress-induced depression / 生理学报

The present study was to investigate the role of the quinolinic acid (QUIN) and its relationship with N-methyl-D-aspartic acid (NMDA) receptor and metabotropic glutamate receptor 1 (mGluR1) in depression induced by chronic unpredictable mild stress (CUMS) in hippocampus. CUMS-induced depression model was established in Sprague-Dawley rats. Intrahippocampal injections of QUIN, QUIN antagonist Ro61-8048, non-competitive NMDA receptor antagonist MK-801 and mGluR1 antagonist AIDA were respectively adopted by rat brain stereotaxic coordinates. The behavioral observations were conducted by measurement of weight changes, sucrose preference test, open-field test and tail suspension test. The concentration of glutamic acid (Glu) and the expression of its receptor subunits in hippocampus were detected by HPLC and Western blot, respectively. The QUIN content in hippocampus was determined by enzyme linked immunosorbent assay (ELISA). The result showed that CUMS significantly induced the depressive-like behaviors in rats, increased the contents of QUIN and Glu, and upregulated the expression of NMDA receptor subunits NR2B and mGluR1 in hippocampus. Microinjection of QUIN into hippocampus resulted in animal depressive-like behaviors, and increased the content of Glu and the expression of NR2B and mGluR1 significantly. QUIN antagonist Ro61-8048 effectively restrained the depression-like behaviors induced by CUMS, and decreased the content of Glu and the expression of NR2B and mGluR1 significantly. Intrahippocampal injections of MK-801 and AIDA effectively improved the depression-like behaviors induced by CUMS and decreased the Glu content. The results suggest that CUMS may contribute to the production and release of QUIN in hippocampal microglia. QUIN results in elevation of Glu level via NMDA receptor and mGluR1, and the increase of expression of NR2B and mGluR1 in hippocampus, which leads to depression-like behaviors in the end.

Modulation of hippocampal glutamate and NMDA/AMPA receptor by homocysteine in chronic unpredictable mild stress-induced rat depression / 生理学报

The study was to investigate the role of homocysteine (Hcy) which was released by hippocampal glial cells and its relationship with NMDA receptor and AMPA receptor in depression induced by chronic unpredictable mild stress (CUMS), and explore the mechanism of changes of Glu/Glu receptor in glial cells and neurons. CUMS-induced depression model was established. The body weight of rats was weighed on the 1st, 7th, 14th, and 21st days during the experiment. The behavioral performances were observed by means of sucrose consumption test, open field test and tail suspension test. Intrahippocampal microinjection of Hcy, NMDA receptor antagonist MK-801 and AMPA receptor antagonist NBQX was performed under stereotaxic guide cannula. The concentration of Glu and the expression of its receptors' subunits were detected respectively by high performance liquid chromatography (HPLC) and Western blot. The Hcy content and the levels of phosphorylation of NMDA receptor and AMPA receptor in hippocampus were separately determined by enzyme linked immunosorbent assay (ELISA). The results showed that CUMS significantly induced the depression-like behaviors in rats, and the content of Glu and Hcy, the expression of NMDA receptors' subunits NR1/NR2B and the level of phosphorylation of NMDA receptor (p-NMDAR) in hippocampus increased significantly, while the expression of AMPA receptors' subunits GluR2/3 and the level of phosphorylation of AMPA receptor (p-AMPAR) decreased significantly. Microinjection of Hcy into hippocampus resulted in similar animal depression-like behaviors and increased Glu content compared to the CON/SAL group, the expression of NR1/NR2B/GluR2/3 and the level of p-NMDAR increased significantly, but the level of p-AMPAR reduced observably. Intrahippocampal injections of MK-801 effectively improved the depression-like behaviors induced by CUMS and Hcy, and attenuated the elevation of Glu content induced by Hcy in hippocampus, whereas NBQX could not improve the depression-like behaviors, but also decreased the Glu content induced by Hcy remarkably. These results suggest that CUMS may contribute to the production and release of Hcy via hippocampal astrocytes. Through the increase of expression of NR1/NR2B/GluR2/3 and level of p-NMDAR, and the decrease of level of p-AMPAR, Hcy results in elevation of Glu level, which leads to depression-like behaviors in the end. In a word, the Hcy released by astrocytes plays an important role in stress-induced elevation of Glu content and variation of NMDA/AMPA receptors in hippocampus.

Ethanolic Extract of the Seed of Zizyphus jujuba var. spinosa Ameliorates Cognitive Impairment Induced by Cholinergic Blockade in Mice

In the present study, we investigated the effect of ethanolic extract of the seed of Zizyphus jujuba var. spinosa (EEZS) on cholinergic blockade-induced memory impairment in mice. Male ICR mice were treated with EEZS. The behavioral tests were conducted using the passive avoidance, the Y-maze, and the Morris water maze tasks. EEZS (100 or 200 mg/kg, p.o.) significantly ameliorated the scopolamine-induced cognitive impairment in our present behavioral tasks without changes of locomotor activity. The ameliorating effect of EEZS on scopolamine-induced memory impairment was significantly reversed by a sub-effective dose of MK-801 (0.0125 mg/kg, s.c.). In addition, single administration of EEZS in normal naive mouse enhanced latency time in the passive avoidance task. Western blot analysis was employed to confirm the mechanism of memory-ameliorating effect of EEZS. Administration of EEZS (200 mg/kg) increased the level of memory-related signaling molecules, including phosphorylation of extracellular signal-regulated kinase or cAMP response element-binding protein in the hippocampal region. Also, the time-dependent expression level of brain-derived neurotrophic factor by the administration of EEZS was markedly increased from 3 to 9 h. These results suggest that EEZS has memory-ameliorating effect on scopolamine-induced cognitive impairment, which is mediated by the enhancement of the cholinergic neurotransmitter system, in part, via NMDA receptor signaling, and that EEZS would be useful agent against cognitive dysfunction such as Alzheimer's disease.

Effect of neuroserpin in a neonatal hypoxic-ischemic injury model ex vivo

Hypoxia-ischemia (HI) occurring in immature brains stimulates the expression of tissue-type plasminogen activator (tPA). Neuroserpin is a selected inhibitor of tPA in the central nerves system. However, the role that neuroserpin plays and the possible mechanisms involved during neonatal HI are poorly defined. In this study, an oxygen-glucose deprivation and reoxygenation (OGD/R) model was generated with cultured rat cortical neurons mimicking neonatal HI injury ex vivo, and an acute neuronal excitatory injury was induced by exposure to a high concentration of N-methyl-D-aspartic acid (NMDA). Cells received either neuroserpin or MK-801, an antagonist of the NMDA receptor, during OGD/R, and were incubated with or without neuroserpin after NMDA exposure. Cell viability and morphology were detected by a Cell Counting Kit-8 and immunohistochemical staining, respectively. TPA expression and activity were also assessed. We found that MK-801 alleviated injuries induced by OGD/R, suggesting an excitatory damage involvement. Neuroserpin provided a dose-dependent neuroprotective effect in both OGD/R and acute excitatory injuries by inhibiting the activity of tPA, without affecting neuronal tPA expression. Neuroserpin protected neurons against OGD/R even after a delayed administration of 3h. Collectively, our data indicate that neuroserpin protects neurons against OGD/R. mainly by inhibiting tPA-mediated acute neuronal excitotoxicity.

MK801 controls form-deprivation myopia by nitric oxide-cyclic GMP signaling pathway in guinea pig / 中南大学学报(医学版)

OBJECTIVE@#To investigate the mechanism of myopia following intravitreous injection of MK801 (dizocipine maleate) intravitreous injected.@*METHODS@#Three-week-old guinea pigs were divided into six groups: group A (control), group B (3 weeks form-deprivation in right eye), group C ( 3 weeks form-deprivation in right eye + saline), group D (3 weeks form-deprivation in right eye + MK801 1ng), group E (3 weeks form-deprivation in right eye + MK801 10 ng), group F (3 weeks form-deprivation in right eye + MK801 100 ng). The refraction and axial length of the eyes were measured. ncNOS was measured by hybridization in situ, and cyclic GMP (cGMP) concentrations by radioimmunochemistry. The correlation between MK801 concentration and diopter degree, axial length of the eyes, and levels of ncNOS or cyclic GMP were analyzed with linear correlation in the groups C-F.@*RESULTS@#Diopter degree was decreased, axial eye length was shorted and levels of ncNOS and c-GMP were decreased in groups C, D, E and F dependent on the concentration of MK801. The diopter degree had positive correlation with MK801 concentration (r=0.702, P<0.05), while the axial eye length and the levels of ncNOS and cGMP were negatively correlated (r=-0.736, -0.637, -0.725, P<0.05)@*CONCLUSION@#MK801 injected into the vitreous humor can restrain myopia by down-regulated the expression of the nitric oxide-cyclic GMP signaling pathway. The effect is concentration dependent.

MK-801 or DNQX reduces electroconvulsive shock-induced impairment of learning-memory and hyperphosphorylation of Tau in rats / 生理学报

This study explored the effect of the excitatory amino acid receptor antagonists on the impairment of learning-memory and the hyperphosphorylation of Tau protein induced by electroconvulsive shock (ECT) in depressed rats, in order to provide experimental evidence for the study on neuropsychological mechanisms improving learning and memory impairment and the clinical intervention treatment. The analysis of variance of factorial design set up two intervention factors which were the electroconvulsive shock (two level: no disposition; a course of ECT) and the excitatory amino acid receptor antagonists (three level: iv saline; iv NMDA receptor antagonist MK-801; iv AMPA receptor antagonist DNQX). Forty-eight adult Wistar-Kyoto (WKY) rats (an animal model for depressive behavior) were randomly divided into six experimental groups (n = 8 in each group): saline (iv 2 mL saline through the tail veins of WKY rats ); MK-801 (iv 2 mL 5 mg/kg MK-801 through the tail veins of WKY rats) ; DNQX (iv 2 mL 5 mg/kg DNQX through the tail veins of WKY rats ); saline + ECT (iv 2 mL saline through the tail veins of WKY rats and giving a course of ECT); MK-801 + ECT (iv 2 mL 5 mg/kg MK-801 through the tail veins of WKY rats and giving a course of ECT); DNQX + ECT (iv 2 mL 5 mg/kg DNQX through the tail veins of WKY rats and giving a course of ECT). The Morris water maze test started within 1 day after the finish of the course of ECT to evaluate learning and memory. The hippocampus was removed from rats within 1 day after the finish of Morris water maze test. The content of glutamate in the hippocampus of rats was detected by high performance liquid chromatography. The contents of Tau protein which included Tau5 (total Tau protein), p-PHF1(Ser396/404), p-AT8(Ser199/202) and p-12E8(Ser262) in the hippocampus of rats were detected by immunohistochemistry staining (SP) and Western blot. The results showed that ECT and the glutamate ionic receptor blockers (NMDA receptor antagonist MK-801 and AMPA receptor antagonist DNQX) induced the impairment of learning and memory in depressed rats with extended evasive latency time and shortened space exploration time. And the two factors presented a subtractive effect. ECT significantly up-regulated the content of glutamate in the hippocampus of depressed rats which were not affected by the glutamate ionic receptor blockers. ECT and the glutamate ionic receptor blockers did not affect the total Tau protein in the hippocampus of rats. ECT up-regulated the hyperphosphorylation of Tau protein in the hippocampus of depressed rats, while the glutamate ionic receptor blockers down-regulated it, and combination of the two factors presented a subtractive effect. Our results indicate that ECT up-regulates the content of glutamate in the hippocampus of depressed rats, which up-regulates the hyperphosphorylation of Tau protein resulting in the impairment of learning and memory in depressed rats.

Effects of propofol and dizocilpine maleate on the cognitive abilities and the hyperphosphorylation of Tau protein of rats after the electroconvulsive therapy / 中国医学科学院学报

<p><b>OBJECTIVE</b>To explore the effects of propofol and dizocilpine maleate (MK-801) on the cognitive abilities the hyperphosphorylation of Tau protein of rats after the electroconvulsive therapy.</p><p><b>METHODS</b>Two intervention factors including electroconvulsive shock therapy (ECT) (two levels: not applied and one treatment course) and drug intervention (three levels: intravenous saline,intravenous MK-801, and intravenous propofol). The morris water maze test started within 1 day after ECT to evaluate the learning-memory. The glutamate level in the hippocampus of rats was determined by high-performance liquid chromatography. The Tau protein that includes Tau5 (total Tau protein), PHF-1 (pSer(396/404)), AT8 (pSer(199/202)), and 12E8 (pSer(262)) in the hippocampus of rats was determined using Western blotting.</p><p><b>RESULTS</b>Propofol, MK-801, and ECT could induce the impairment of learning-memory in depressed rats. The electroconvulsive shock significantly up-regulated the glutamate level, which was reduces by the propofol. The ECT up-regulated the hyperphosphorylation of Tau protein in the hippocampus of depressed rats, which was reduced by propofol and MK-801.</p><p><b>CONCLUSION</b>Both propofol and MK-801 could protect against the impairment of learning-memory and reduce the hyperphosphorylation of Tau protein induced by ECT in depressed rats.</p>