MK-801 Increases Extracellular 5-Hydroxytryptamine in Rat Hippocampus and Striatum In Vivo

The effect of MK-801 (0.25 or 0.5 mg/kg) on the extracellular concentration of 5-hydroxytryptamine (5-HT) and 5-hydroxyindoleacetic acid (5-HIAA) in rat hippocampus and striatum was studied using intracerebral dialysis. The dialysate 5-HT concentration was dose-dependently increased by MK-801 in both regions. In the hippocampus, at the higher drug dose a slow increase in the 5-HIAA level was observed, and this became significant 3 h after treatment. In contrast to this, the extracellular 5-HIAA content in the striatum was significantly decreased 150 min after administration of both doses of MK-801. The data are discussed in the light of the known behavioural effects of MK-801 and possible N-methyl-D-aspartic acid receptor regulation of 5-HT release.     

Metabolomic Analysis Reveals Extended Metabolic Consequences of Marginal Vitamin B-6 Deficiency in Healthy Human Subjects

Marginal deficiency of vitamin B-6 is common among segments of the population worldwide. Because pyridoxal 5′-phosphate (PLP) serves as a coenzyme in the metabolism of amino acids, carbohydrates, organic acids, and neurotransmitters, as well as in aspects of one-carbon metabolism, vitamin B-6 deficiency could have many effects. Healthy men and women (age: 20-40 y; n = 23) were fed a 2-day controlled, nutritionally adequate diet followed by a 28-day low-vitamin B-6 diet (<0.5 mg/d) to induce marginal deficiency, as reflected by a decline of plasma PLP from 52.6±14.1 (mean ± SD) to 21.5±4.6 nmol/L (P<0.0001) and increased cystathionine from 131±65 to 199±56 nmol/L (P<0.001). Fasting plasma samples obtained before and after vitamin B6 restriction were analyzed by ¹H-NMR with and without filtration and by targeted quantitative analysis by mass spectrometry (MS). Multilevel partial least squares-discriminant analysis and S-plots of NMR spectra showed that NMR is effective in classifying samples according to vitamin B-6 status and identified discriminating features. NMR spectral features of selected metabolites indicated that vitamin B-6 restriction significantly increased the ratios of glutamine/glutamate and 2-oxoglutarate/glutamate (P<0.001) and tended to increase concentrations of acetate, pyruvate, and trimethylamine-N-oxide (adjusted P<0.05). Tandem MS showed significantly greater plasma proline after vitamin B-6 restriction (adjusted P<0.05), but there were no effects on the profile of 14 other amino acids and 45 acylcarnitines. These findings demonstrate that marginal vitamin B-6 deficiency has widespread metabolic perturbations and illustrate the utility of metabolomics in evaluating complex effects of altered vitamin B-6 intake.     

亚慢性地卓西平诱导的精神分裂样小鼠前额叶和海马脑区MIF蛋白表达的变化

目的:探讨亚慢性地卓西平(MK-801)诱导的精神分裂样小鼠模型中前额叶和海马脑区巨噬细胞迁移抑制因子(Macrophage migration inhibitory factor,MIF)蛋白表达的变化。方法:将24只7周龄小鼠随机分为对照组、MK-801组和MK-801+奥氮平(olanzapine,olz)组(n=8),三组小鼠分别接受0.9%生理盐水、MK-801(0.6 mg/kg)和MK-801(0.6 mg/kg)+奥氮平(2.5 mg/kg)给药,持续4周。小鼠行为学通过旷场试验、社交实验进行评价,免疫印迹法检测小鼠前额叶和海马组织中MIF蛋白的表达。结果:MK-801处理后,小鼠活动量增加,社交功能受损,且都能被抗精神分裂症药物奥氮平显著改善。MK-801组小鼠前额叶皮层中MIF蛋白表达与对照组比较无明显统计学差异(P0.05),而海马脑区中MIF蛋白表达较对照组明显升高(P0.05);MK-801+奥氮平组小鼠前额叶皮层中MIF蛋白表达较MK-801组无显著变化,而海马脑区中MIF蛋白表达较MK-801组明显降低(P0.05)。结论:亚慢性给予MK-801诱导的精神分裂样小鼠海马脑区中MIF蛋白水平升高,提示MIF蛋白可能参与MK-801诱导的精神分裂样行为。     

Exploratory Metabolomic Analyses Reveal Compounds Correlated with Lutein Concentration in Frontal Cortex,Hippocampus, and Occipital Cortex of Human Infant Brain

Lutein is a dietary carotenoid well known for its role as an antioxidant in the macula, and recent reports implicate a role for lutein in cognitive function. Lutein is the dominant carotenoid in both pediatric and geriatric brain tissue. In addition, cognitive function in older adults correlated with macular and postmortem brain lutein concentrations. Furthermore, lutein was found to preferentially accumulate in the infant brain in comparison to other carotenoids that are predominant in diet. While lutein is consistently related to cognitive function, the mechanisms by which lutein may influence cognition are not clear. In an effort to identify potential mechanisms through which lutein might influence neurodevelopment, an exploratory study relating metabolite signatures and lutein was completed. Post-mortem metabolomic analyses were performed on human infant brain tissues in three regions important for learning and memory: the frontal cortex, hippocampus, and occipital cortex. Metabolomic profiles were compared to lutein concentration, and correlations were identified and reported here. A total of 1276 correlations were carried out across all brain regions. Of 427 metabolites analyzed, 257 were metabolites of known identity. Unidentified metabolite correlations (510) were excluded. In addition, moderate correlations with xenobiotic relationships (2) or those driven by single outliers (3) were excluded from further study. Lutein concentrations correlated with lipid pathway metabolites, energy pathway metabolites, brain osmolytes, amino acid neurotransmitters, and the antioxidant homocarnosine. These correlations were often brain region—specific. Revealing relationships between lutein and metabolic pathways may help identify potential candidates on which to complete further analyses and may shed light on important roles of lutein in the human brain during development.     

Metabolic Changes in Cerebral Cortex, Hippocampus, and Cerebellum During Sustained Bicuculline-Induced Seizures

Abstract— The objective of the present experiments was to study metabolic correlates to the localization of neuronal lesions during sustained seizures. To that end, status epilepticus was induced by i.v. administration of bicuculline in immobilized and artificially ventilated rats, since this model is known to cause neuronal cell damage in cerebral cortex and hippocampus but not in the cerebellum. After 20 or 120 min of continuous seizure activity, brain tissue was frozen in situ through the skull bone, and samples of cerebral cortex, hippocampus, and cerebellum were collected for analysis of glycolytic metabolites, phosphocreatine (PCr), ATP, ADP, AMP, and cyclic nucleotides. After 20 min of seizure activity, the two “vulnerable” structures (cerebral cortex and hippocampus) and the “resistant” one (cerebellum) showed similar changes in cerebral metabolic state, characterized by decreased tissue concentrations of PCr, ATP, and glycogen, and increased lactate concentrations and lactate/ pyruvate ratios. In all structures, though, the adenylate energy charge remained close to control. At the end of a 2-h period of status epilepticus, a clear deterioration of the energy state was observed in the cerebral cortex and the hippocampus, but not in the cerebellum. The reduction in adenylate energy charge in the cortex and hippocampus was associated with a seemingly paradoxical decrease in tissue lactate levels and with failure of glycogen resynthesis (cerebral cortex). Experiments with infusion of glucose during the second hour of a 2-h period of status epilepticus verified that the deterioration of tissue energy state was partly due to reduced substrate supply; however, even in animals with adequate tissue glucose concentrations, the energy charge of the two structures was significantly lowered. The cyclic nucleotides (cAMP and cGMP) behaved differently. Thus, whereas cAMP concentrations were either close to control (hippocampus and cerebellum) or moderately increased (cerebral cortex), the cGMP concentrations remained markedly elevated throughout the seizure period, the largest change being observed in the cerebellum. It is concluded that although the localization of neuronal damage and perturbation of cerebral energy state seem to correlate, the results cannot be taken as. evidence that cellular energy failure is the cause of the damage. Thus, it appears equally probable that the pathologically enhanced neuronal activity (and metabolic rate) underlies both the cell damage and the perturbed metabolic state. The observed changes in cyclic nucleotides do not appear to bear a causal relationship to the mechanisms of damage.     

Rhythmic Pruning of Perceptual Noise for Object Representation in the Hippocampus and Perirhinal Cortex in Rats

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MK-801 is a potent nematocidal agent. Characterization of MK-801 binding sites in Caenorhabditis elegans.

MK-801, an N-methyl-D-aspartate antagonist in mammalian brain tissue, is a potent nematocidal agent. Specific MK-801 binding sites have been identified and characterized in a membrane fraction prepared from the free-living nematode Caenorhabditis elegans. The high-affinity MK-801 binding site has an apparent dissociation constant, Kd, of 225 nM. Unlike the MK-801 binding site in mammalian tissues, the C. elegans binding site is not effected by glutamate or glycine, and polyamines are potent inhibitors of specific MK-801 binding.     

GnRH—a对大鼠海马和皮质部位parvalbumin表达的影响

目的：研究促性腺激素释放激素类似物（gonadotropin releasing hormone analogue,GnRH-a）对大鼠海马、皮质部位小白蛋白（parvalbumin,PV）表达的影响。方法：采用酶联免疫吸附试验测定血清激素水平,免疫组织化学和图像分析观察大鼠海马、皮质部位PV的表达。结果：①GnRH-a组大鼠血清雌二醇（estradiol,E2）、LH及FSH水平较正常对照组下降,差异有统计学意义（P〈0.05）;与OVX组比较LH、FSH较低,差异有统计学意义（P〈0.05）,但E2差异不显著。②正常情况下,大鼠海马、皮质部位可观察到PV神经元及纤维分布。③GnRH-a组PV细胞数及灰度值低于正常对照组,差异有统计学意义（P〈0.05）,与去卵巢组大鼠组相似;GnRH-a＋E2联合用药后,PV细胞数及灰度值与正常对照组相似。结论：GnRH-a降低大鼠海马、皮质部位神经元中PV的表达,从而影响神经元的功能,这可能与其用药后神经精神副反应有一定关系。     

创伤后应激障碍大鼠海马与前额叶皮质中OREXIN受体的失调

目的:从食欲素(Orexin, ORX)系统挖掘创伤后应激障碍的神经生物学机制。方法:以单次延长刺激(single prolonged stimulation,SPS)法复制创伤后应激障碍(post traumatic stress disorder,PTSD)大鼠模型,以行为学结合血清中皮质酮和神经元特异性烯醇化酶进行模型评价,通过酶联免疫吸附试验(Elisa)分析大鼠血清与脑脊液中OREXIN水平,以实时荧光定量聚合酶链反应(RT-PCR)检测海马与前额叶皮质中的Orexin受体基因表达。结果:实验成功的复制了PTSD模型,与对照组相比,模型组大鼠血清中皮质酮和神经元特异性烯醇化酶的含量均极显著升高(P0.01),脑脊液中Orexin A、Orexin B的含量均显著升高(P0.01),海马和皮质中ORX1R与ORX2R均极显著下降(P0.01)。结论:PTSD大鼠的应激损伤与Orexin及其受体表达水平的变化密切相关。     

GnRH-a对大鼠海马和皮质部位parvalbumin表达的影响

目的:研究促性腺激素释放激素类似物(gonadotropin releasing hormone analogue,GnRH-a)对大鼠海马、皮质部位小白蛋白(parvalbumin,PV)表达的影响.方法:采用酶联免疫吸附试验测定血清激素水平,免疫组织化学和图像分析观察大鼠海马、皮质部位PV的表达.结果:①GnRH-a组大鼠血清雌二醇(estradiol,E2)、LH及FSH水平较正常对照组下降,差异有统计学意义(P<0.05);与OVX组比较LH、FSH较低,差异有统计学意义(P<0.05),但E2差异不显著.②正常情况下,大鼠海马、皮质部位可观察到PV神经元及纤维分布.③GnRH-a组PV细胞数及灰度值低于正常对照组,差异有统计学意义(P<0.05),与去卵巢组大鼠组相似;GnRH-a+E2联合用药后,PV细胞数及灰度值与正常对照组相似.结论:GnRH-a降低大鼠海马、皮质部位神经元中PV的表达,从而影响神经元的功能,这可能与其用药后神经精神副反应有一定关系.     

Experimental Evidence that Phenylalanine Provokes Oxidative Stress in Hippocampus and Cerebral Cortex of Developing Rats

High levels of phenylalanine (Phe) are the biochemical hallmark of phenylketonuria (PKU), a neurometabolic disorder clinically characterized by severe mental retardation and other brain abnormalities, including cortical atrophy and microcephaly. Considering that the pathomechanisms leading to brain damage and particularly the marked cognitive impairment in this disease are poorly understood, in the present study we investigated the in vitro effect of Phe, at similar concentrations as to those found in brain of PKU patients, on important parameters of oxidative stress in the hippocampus and cerebral cortex of developing rats. We found that Phe induced in vitro lipid peroxidation (increase of TBA-RS values) and protein oxidative damage (sulfhydryl oxidation) in both cerebral structures. Furthermore, these effects were probably mediated by reactive oxygen species, since the lipid oxidative damage was totally prevented by the free radical scavengers α-tocopherol and melatonin, but not by L-NAME, a potent inhibitor of nitric oxide synthase. Accordingly, Phe did not induce nitric oxide synthesis, but significantly decreased the levels of reduced glutathione (GSH), the major brain antioxidant defense, in hippocampus and cerebral cortex supernatants. Phe also reduced the thiol groups of a commercial GSH solution in a cell-free medium. We also found that the major metabolites of Phe catabolism, phenylpyruvate, phenyllactate and phenylacetate also increased TBA-RS levels in cerebral cortex, but to a lesser degree. The data indicate that Phe elicits oxidative stress in the hippocampus, a structure mainly involved with learning/memory, and also in the cerebral cortex, which is severely damaged in PKU patients. It is therefore presumed that this pathomechanism may be involved at least in part in the severe cognitive deficit and in the characteristic cortical atrophy associated with dysmyelination and leukodystrophy observed in this disorder.     

Administration of Histidine to Female Rats Induces Changes in Oxidative Status in Cortex and Hippocampus of the Offspring

Histidinemia is an inherited metabolic disorder biochemically characterized by high concentrations of histidine in biological fluids. Usually affected patients are asymptomatic although some individuals have mental retardation and speech disorders. Considering the high prevalence of histidinemia and the scarce information on the effects of maternal histidinemia on their progeny, we investigated various parameters of oxidative stress in brain cortex and hippocampus of the offspring from female rats that received histidine (0.5 mg/g of body weight) in the course of pregnancy and lactation. At 21 days of age we found a significant increase of thiobarbituric acid reactive substances (TBARS), 2′,7′-dihydrodichlorofluorescein oxidation, superoxide dismutase (SOD) activity, catalase (CAT) activity, total sulfhydryls and glutathione (GSH) content in cerebral cortex and hippocampus. We also verified that at 60 days of age, GSH, SOD and total sulfhydryls returned to normal levels in brain cortex, while the other parameters decreased in the same structure. In the hippocampus, at 60 days of age GSH returned to normal levels, CAT persisted elevated and the other parameters decreased. These results indicate that histidine administration to female rats can induce oxidative stress in the brain from the offspring, which partially recovers 40 days after breastfeeding stopped.     

Learning-Induced Gene Expression in the Hippocampus Reveals a Role of Neuron -Astrocyte Metabolic Coupling in Long Term Memory

We examined the expression of genes related to brain energy metabolism and particularly those encoding glia (astrocyte)-specific functions in the dorsal hippocampus subsequent to learning. Context-dependent avoidance behavior was tested in mice using the step-through Inhibitory Avoidance (IA) paradigm. Animals were sacrificed 3, 9, 24, or 72 hours after training or 3 hours after retention testing. The quantitative determination of mRNA levels revealed learning-induced changes in the expression of genes thought to be involved in astrocyte-neuron metabolic coupling in a time dependent manner. Twenty four hours following IA training, an enhanced gene expression was seen, particularly for genes encoding monocarboxylate transporters 1 and 4 (MCT1, MCT4), alpha2 subunit of the Na/K-ATPase and glucose transporter type 1. To assess the functional role for one of these genes in learning, we studied MCT1 deficient mice and found that they exhibit impaired memory in the inhibitory avoidance task. Together, these observations indicate that neuron-glia metabolic coupling undergoes metabolic adaptations following learning as indicated by the change in expression of key metabolic genes.     

Neuronal Loss and Cytoskeletal Disruption Following Intrahippocampal Administration of the Metabolic Inhibitor Malonate: Lack of Protection by MK-801

Abstract: Impaired energy metabolism may contribute to the pathogenesis of late-onset neurodegenerative disorders such as Alzheimer's disease by increasing neuronal vulnerability to excitotoxic damage through the NMDA receptor. The effects of metabolic impairment on the striatum have been extensively examined, but relatively little is known regarding the vulnerability of the hippocampus. To examine the effect of metabolic impairment on the hippocampal formation, malonate (0.25–2.5 µmol), a reversible inhibitor of succinate dehydrogenase, was administered by stereotaxic injection into the hippocampus of male Sprague-Dawley rats. Neuronal loss was assessed by Nissl stain, and immunocytochemistry was used to examine cytoskeletal disruption. Malonate produced a dose-dependent lesion in which CA1 pyramidal neurons were most vulnerable, followed by CA3 and dentate gyrus. Cytoskeletal alterations included the loss of microtubule-associated protein 2 (MAP2) and dendritic MAP1B immunoreactivity, whereas axonal MAP1B and τ proteins were relatively spared. Spatially and temporally correlated with the loss of MAP2 was an increase in the immunoreactivity of calpain-cleaved spectrin. A similar pattern of neuronal damage and cytoskeletal disruption was produced by intrahippocampal injection of quinolinate (0.1 µmol), an NMDA agonist. Although these results are consistent with the hypothesis that metabolic impairment results in excitotoxic death, MK-801 (dizocilpine maleate), a noncompetitive NMDA receptor antagonist, did not attenuate the lesions produced by malonate but was effective against quinolinate. The results suggest that NMDA receptor activation is not required for malonate-induced damage in the hippocampal formation.     

Behavioral effects of MK-801 in morphine-dependent and non-dependent mice

The behavioral effects of MK-801 were compared in morphine-dependent and non-dependent mice. The dose of MK-801 selected for these studies was previously demonstrated to attenuate some of the morphine withdrawal signs. Subjects were repeatedly exposed to morphine (8 days, b.i.d., 10–100 mg/kg, s.c.). Twenty-four hours after last morphine injection mice received naloxone (0.1 mg/kg, s.c.) and the observation was commenced. Animals were pretreated with either MK-801 (0.1 mg/kg, i.p.) or saline 30 min prior to testing. It was found that the behavioral effects of MK-801 (decreased sociability and increased rate of transitions between behavioral elements, locomotion, grooming) were less pronounced in morphine-dependent compared to non-dependent subjects. However, the intensified almost stereotypic eating possibly reflected increased psychotomimetic potency of MK-801 in morphine-withdrawn animals.     

Examination of Parameters Influencing [3H]MK-801 Binding in Postmortem Human Cortex

[3H]MK-801 binding was used as an index of the glutamate receptor N-methyl-D-aspartate-subtype channel to examine the influence of gender, age, mode of death (agonal status), interval between death and autopsy (postmortem delay), and time in storage at -70 degrees C in well washed homogenate preparations from postmortem human frontal cortex. Basal binding and the modulatory effects of glutamate, glycine, spermidine, and zinc were examined with respect to these variables. Basal binding was sensitive to agonal status, being higher in sudden death cases. The effect of added glutamate and glycine was sensitive to age, with a trend toward lower binding with increasing age. The effect of added spermidine alone was sensitive to storage time at -70 degrees C, the binding being higher with longer storage time. The effect of added zinc was also sensitive to postmortem delay, with zinc causing a greater reduction in binding with shorter postmortem delays. Thus, with the exception of gender, all variables examined influenced [3H]MK-801 binding, highlighting the attention that should be given to these factors in postmortem studies in normal and diseased human subjects.     

Intracerebroventricular Administration of Ouabain to Rats Changes the Expression of NMDA Receptor Subunits in Cerebral Cortex and Hippocampus

Ouabain exerts neurotoxic action and activates the population of NMDA receptors. Herein the effect of ouabain on the expression of NMDA subunits was evaluated. Adult Wistar rats were administered intracerebroventricularly with 0.1, 10 and 100 nmol ouabain or saline solution (control). Two days later, membranes of cerebral cortex and hippocampus were isolated. Western blots with antibodies for the NMDA receptor subunits: NR1; NR2A; NR2B; NR2C and NR2D were carried out. In cerebral cortex, NR2D subunit increased 30% with 10 nmol ouabain dose. With 100 nmol ouabain, NR1 and NR2D subunits enhanced 40 and 20%, respectively. In hippocampus, with the dose of 0.1 nmol ouabain, NR1 subunit enhanced roughly 50% whereas NR2B subunit decreased 30%. After administration of 10 nmol ouabain dose, NR2A, NR2B and NR2C subunits decreased 40, 50 and 30%, respectively. With the dose of 100 nmol of ouabain, NR1, NR2A and NR2B subunits diminished 10–20%. It is concluded that ouabain administration led to a differential regulation in the expression of NMDA subunits. These results may be correlated with the modulatory action of ouabain on NMDA receptor.     

GPR50 Distribution in the Mouse Cortex and Hippocampus

Neurochemical Research - G protein-coupled receptor 50 (GPR50) belongs to the G protein-coupled receptor which is highly homologous with the sequence of melatonin receptor MT1 and MT2. GPR50...     

Fluoride and Arsenic Exposure Impairs Learning and Memory and Decreases mGluR5 Expression in the Hippocampus and Cortex in Rats

Fluoride and arsenic are two common inorganic contaminants in drinking water that are associated with impairment in child development and retarded intelligence. The present study was conducted to explore the effects on spatial learning, memory, glutamate levels, and group I metabotropic glutamate receptors (mGluRs) expression in the hippocampus and cortex after subchronic exposure to fluoride, arsenic, and a fluoride and arsenic combination in rats. Weaned male Sprague-Dawley rats were assigned to four groups. The control rats drank tap water. Rats in the three exposure groups drank water with sodium fluoride (120 mg/L), sodium arsenite (70 mg/L), and a sodium fluoride (120 mg/L) and sodium arsenite (70 mg/L) combination for 3 months. Spatial learning and memory was measured in Morris water maze. mGluR1 and mGluR5 mRNA and protein expression in the hippocampus and cortex was detected using RT-PCR and Western blot, respectively. Compared with controls, learning and memory ability declined in rats that were exposed to fluoride and arsenic both alone and combined. Combined fluoride and arsenic exposure did not have a more pronounced effect on spatial learning and memory compared with arsenic and fluoride exposure alone. Compared with controls, glutamate levels decreased in the hippocampus and cortex of rats exposed to fluoride and combined fluoride and arsenic, and in cortex of arsenic-exposed rats. mGluR5 mRNA and protein expressions in the hippocampus and mGluR5 protein expression in the cortex decreased in rats exposed to arsenic alone. Interestingly, compared with fluoride and arsenic exposure alone, fluoride and arsenic combination decreased mGluR5 mRNA expression in the cortex and protein expression in the hippocampus, suggesting a synergistic effect of fluoride and arsenic. These data indicate that fluoride and arsenic, either alone or combined, can decrease learning and memory ability in rats. The mechanism may be associated with changes of glutamate level and mGluR5 expression in cortex and hippocampus.