Astrocytic endothelin-1 overexpression impairs learning and memory ability in ischemic stroke via altered hippocampal neurogenesis and lipid metabolism

Vascular etiology is the second most prevalent cause of cognitive impairment globally.Endothelin-1,which is produced and secreted by endothelial cells and astrocytes,is implicated in the pathogenesis of stroke.However,the way in which changes in astrocytic endothelin-1 lead to poststroke cognitive deficits following transient middle cerebral artery occlusion is not well understood.Here,using mice in which astrocytic endothelin-1 was overexpressed,we found that the selective overexpression of endothelin-1 by astrocytic cells led to ischemic stroke-related dementia(1 hour of ischemia;7 days,28 days,or 3 months of reperfusion).We also revealed that astrocytic endothelin-1 overexpression contributed to the role of neural stem cell proliferation but impaired neurogenesis in the dentate gyrus of the hippocampus after middle cerebral artery occlusion.Comprehensive proteome profiles and western blot analysis confirmed that levels of glial fibrillary acidic protein and peroxiredoxin 6,which were differentially expressed in the brain,were significantly increased in mice with astrocytic endothelin-1 overexpression in comparison with wild-type mice 28 days after ischemic stroke.Moreover,the levels of the enriched differentially expressed proteins were closely related to lipid metabolism,as indicated by Kyoto Encyclopedia of Genes and Genomes pathway analysis.Liquid chromatography-mass spectrometry nontargeted metabolite profiling of brain tissues showed that astrocytic endothelin-1 overexpression altered lipid metabolism products such as glycerol phosphatidylcholine,sphingomyelin,and phosphatidic acid.Overall,this study demonstrates that astrocytic endothelin-1 overexpression can impair hippocampal neurogenesis and that it is correlated with lipid metabolism in poststroke cognitive dysfunction.

Recombinant chitinase-3-like protein 1 alleviates learning and memory impairments via M2 microglia polarization in postoperative cognitive dysfunction mice

Postoperative cognitive dysfunction is a seve re complication of the central nervous system that occurs after anesthesia and surgery,and has received attention for its high incidence and effect on the quality of life of patients.To date,there are no viable treatment options for postoperative cognitive dysfunction.The identification of postoperative cognitive dysfunction hub genes could provide new research directions and therapeutic targets for future research.To identify the signaling mechanisms contributing to postoperative cognitive dysfunction,we first conducted Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway enrichment analyses of the Gene Expression Omnibus GSE95426 dataset,which consists of mRNAs and long non-coding RNAs differentially expressed in mouse hippocampus3 days after tibial fracture.The dataset was enriched in genes associated with the biological process"regulation of immune cells,"of which Chill was identified as a hub gene.Therefore,we investigated the contribution of chitinase-3-like protein 1 protein expression changes to postoperative cognitive dysfunction in the mouse model of tibial fractu re surgery.Mice were intraperitoneally injected with vehicle or recombinant chitinase-3-like protein 124 hours post-surgery,and the injection groups were compared with untreated control mice for learning and memory capacities using the Y-maze and fear conditioning tests.In addition,protein expression levels of proinflammatory factors(interleukin-1βand inducible nitric oxide synthase),M2-type macrophage markers(CD206 and arginase-1),and cognition-related proteins(brain-derived neurotropic factor and phosphorylated NMDA receptor subunit NR2B)were measured in hippocampus by western blotting.Treatment with recombinant chitinase-3-like protein 1 prevented surgery-induced cognitive impairment,downregulated interleukin-1βand nducible nitric oxide synthase expression,and upregulated CD206,arginase-1,pNR2B,and brain-derived neurotropic factor expression compared with vehicle treatment.Intraperitoneal administration of the specific ERK inhibitor PD98059 diminished the effects of recombinant chitinase-3-like protein 1.Collectively,our findings suggest that recombinant chitinase-3-like protein 1 ameliorates surgery-induced cognitive decline by attenuating neuroinflammation via M2 microglial polarization in the hippocampus.Therefore,recombinant chitinase-3-like protein1 may have therapeutic potential fo r postoperative cognitive dysfunction.

Effects of exercise on neurogenesis in the dentate gyrus and ability of learning and memory after hippocampus lesion in adult rats

Objective To explore the effects of exercise on dentate gyrus （DG） neurogenesis and the ability of learning and memory in hippocampus-lesioned adult rats. Methods Hippocampus lesion was produced by intrabippocampal microinjection of kainic acid （KA）. Bromodeoxyuridine （BrdU） was used to label dividing cells. Y maze test was used to evaluate the ability of learning and memory. Exercise was conducted in the form of forced running in a motor-driven running wheel. The speed of wheel revolution was regulated at 3 kinds of intensity： lightly running, moderately running, or heavily running. Results Hippocampus lesion could increase the number of BrdU-labeled DG cells, moderately running after lesion could further enhance the number of BrdU-labeled cells and decrease the error number （EN） in Y maze test, while neither lightly running, nor heavily running had such effects. There was a negative correlation between the number of DG BrdU-labeled cells and the EN in the Y maze test after running. Conclusion Moderate exercise could enhance the DG neurogenesis and ameliorate the ability of learning and memory in hippocampus-lesioned rats.

Mannotriose regulates learning and memory signal transduction in the hippocampus

Rehmannia is a commonly used Chinese herb, which improves ieaming and memory. However, the crucial components of the signal transduction pathway associated with this effect remain elusive. Pri- mary hippocampal neurons were cultured in vitro, insulted with high-concentration （1 × 10-4 mol/L） cor- ticosterone, and treated with 1 × 104 mol/L mannotriose. Thiazolyl blue tetrazolium bromide assay and western blot analysis showed that hippocampal neuron survival rates and protein levels of glucocorti- cold receptor, serum and glucocorticoid-regulated protein kinase, and brain-derived neurotrophic factor were all dramatically decreased after high-concentration corticosterone-induced injury. This effect was reversed by mannotriose, to a similar level as RU38486 and donepezil. Our findings indicate that mannotriose could protect hippocampal neurons from high-concentration corticosterone-induced injury. The mechanism by which this occurred was associated with levels of glucocorticoid receptor protein, serum and glucocorticoid-regulated protein kinase, and brain-derived neurotrophic factor.

Treadmill exercise improves hippocampal neural plasticity and relieves cognitive deficits in a mouse model of epilepsy

Epilepsy frequently leads to cognitive dysfunction and approaches to treatment remain limited.Although regular exercise effectively improves learning and memory functions across multiple neurological diseases,its application in patients with epilepsy remains controversial.Here,we adopted a 14-day treadmill-exercise paradigm in a pilocarpine injection-induced mouse model of epilepsy.Cognitive assays confirmed the improvement of object and spatial memory after endurance training,and electrophysiological studies revealed the maintenance of hippocampal plasticity as a result of physical exercise.Investigations of the mechanisms underlying this effect revealed that exercise protected parvalbumin interneurons,probably via the suppression of neuroinflammation and improved integrity of blood-brain barrier.In summary,this work identified a previously unknown mechanism through which exercise improves cognitive rehabilitation in epilepsy.

Exercise-with-melatonin therapy improves sleep disorder and motor dysfunction in a rat model of ischemic stroke

Exercise-with-melatonin therapy has complementary and synergistic effects on spinal cord injury and Alzheimer's disease,but its effect on stroke is still poorly understood.In this study,we established a rat model of ischemic stroke by occluding the middle cerebral artery for 60 minutes.We treated the rats with exercise and melatonin therapy for 7 consecutive days.Results showed that exercise-with-melatonin therapy significantly prolonged sleep duration in the model rats,increased delta power values,and regularized delta power rhythm.Additionally,exercise-with-melatonin therapy improved coordination,endurance,and grip strength,as well as learning and memory abilities.At the same time,it led to higher hippocampal CA1 neuron activity and postsynaptic density thickness and lower expression of glutamate receptor 2 than did exercise or melatonin therapy alone.These findings suggest that exercise-withmelatonin therapy can alleviate sleep disorder and motor dysfunction by increasing glutamate receptor 2 protein expression and regulating hippocampal CA1 synaptic plasticity.

Exercise preconditioning alleviates ischemia-induced memory deficits by increasing circulating adiponectin

Cerebral ischemia is a major health risk that requires preventive approaches in addition to drug therapy.Physical exercise enhances neurogenesis and synaptogenesis,and has been widely used for functional rehabilitation after stroke.In this study,we determined whether exercise training before disease onset can alleviate the severity of cerebral ischemia.We also examined the role of exercise-induced circulating factors in these effects.Adult mice were subjected to 14 days of treadmill exercise training before surgery for middle cerebral artery occlusion.We found that this exercise pre-conditioning strategy effectively attenuated brain infarct area,inhibited gliogenesis,protected synaptic proteins,and improved novel object and spatial memory function.Further analysis showed that circulating adiponectin plays a critical role in these preventive effects of exercise.Agonist activation of adiponectin receptors by Adipo Ron mimicked the effects of exercise,while inhibiting receptor activation abolished the exercise effects.In summary,our results suggest a crucial role of circulating adiponectin in the effects of exercise pre-conditioning in protecting against cerebral ischemia and supporting the health benefits of exercise.

Role of the hippocampus on learning and memory functioning and pain modulation

The hippocampus, an important part of the limbic system, is considered to be an important region of the brain for learning and memory functioning. Recent studies have demonstrated that synaptic plasticity is thought to be the basis of learning and memory functioning. A series of studies report that similar synaptic plasticity also exists in the spinal cord in the conduction pathway of pain sensation, which may contribute to hyperalgesia, abnormal pain, and analgesia. The synaptic plasticity of learning and memory functioning and that of the pain conduction pathway have similar mechanisms, which are related to the N-methyl-D-aspartic acid receptor. The hippocampus also has a role in pain modulation. As pain signals can reach the hippocampus, the precise correlation between synaptic plasticity of the pain pathway and that of learning and memory functioning deserves further investigation. The role of the hippocampus in processing pain information requires to be identified.

Potential Association of Lead Exposure During Early Development of Mice With Alteration of Hippocampus Nitric Oxide Levels and Learning Memory

Objective Chronic lead （Pb） exposure during development is known to produce learning deficits. Nitric oxide participates in the synaptic mechanisms involved in certain forms of learning and memory. This study was designed to clarify whether Pb-induced impairment in learning and memory was associated with the changes of nitric oxide levels in mice brains. Methods Sixty Balb/c mice aged l0 days were chosen. A model of lead exposure was established by drinking 0.025%, 0.05% 0.075% lead acetate, respectively for 8 weeks. The controls were orally given distilled water. The ability to learn and memorize was examined by open field test, T-water maze test. In parallel with the behavioral data, NO level of hippocampus tissue was detected by biochemical assay. Results Compared with control groups, （1） the weight of 0.075% group was significantly reduced （P〈0.05）; （2） The number of times in mice attaining the required standards in T-water maze test was lower in 0.075% group （P〈0.01）. No significant difference was found between experimental and control groups in open field test （P〉0.05）; （3） NO level of mouse hippocampus tissue was decreased in 0.075% group （P〈0.01）. Conclusions The findings suggest that decreased hippocampus NO level may contribute to the Pb-induced deficits in learning and memory processes.

Similar effects of substance P on learning and memory function between hippocampus and striatal marginal division

Substance P is an endogenous neurokinin that is present in the central and peripheral nervous systems. The neuropeptide substance P and its high-affinity receptor neurokinin 1 receptor are known to play an important role in the central nervous system in inflammation, blood pressure, motor behavior and anxiety. The effects of substance P in the hippocampus and the marginal di- vision of the striatum on memory remain poorly understood. Compared with the hippocampus as a control, immunofluorescence showed high expression of the substance P receptor, neuro- kinin 1, in the marginal division of the striatum of normal rats. Unilateral or bilateral injection of an antisense oligonucleotide against neurokinin 1 receptor mRNA in the rat hippocampus or marginal division of the striatum effectively reduced neurokinin 1 receptor expression. Indepen- dent of injection site, rats that received this antisense oligonucleotide showed obviously increased footshock times in a Y-maze test. These results indicate that the marginal division of the striatum plays a similar function in learning and memory to the hippocampus, which is a valuable addi- tion to our mechanistic understanding of the learning and memory functions of the marginal division of the striatum.

Influence of acupuncture with exercise training on learning and memory functions, as well as microtubule-associated protein-2 and synaptophysin expression in the hippocampal CA3 region, in a rat model of cerebral infarction

The present study was designed to determine microtubule-associated protein-2 and synaptophysin expression in the hippocampal CA3 region in a rat model of middle cerebral artery occlusion. The rats were treated with acupuncture at Baihui （GV 20）, Qubin （GB 7）, and Qianding （GV 21） points, in addition to exercise training. Results were compared with rats undergoing exercise training only. The Y-maze method and immunohistochemistry revealed decreased error frequency of passing through Y-maze, as well as significantly increased microtubule-associated protein-2 and synaptophysin expression, in the acupuncture with exercise training group compared with the model and exercise training groups after 5 weeks. Microtubule-associated protein-2 and synaptophysin expressions negatively correlated with error frequency of passing through the Y-maze. These results suggested that acupuncture combined with exercise training improved learning and memory functions in a rat model of cerebral infarction. The mechanisms of action were hypothesized to be associated with dendritic or synaptic plasticity in the ipsilateral hippocampal CA3 region.

Chlorogenic acid protection of neuronal nitric oxide synthase-positive neurons in the hippocampus of mice with impaired learning and memory

BACKGROUND： Clinical practice and modern pharmacology have confirmed that chlorogenic acid can ameliorate learning and memory impairments. OBJECTIVE： To observe the effects of chlorogenic acid on neuronal nitric oxide synthase （nNOS）-positive neurons in the mouse hippocampus, and to investigate the mechanisms underlying the beneficial effects of chlorogenic acid on learning and memory. DESIGN, TIME AND SETTING： The present randomized, controlled, neural cell morphological observation was performed at the Institute of Neurobiology, Central South University between January and May 2005. MATERIALS： Forty-eight female, healthy, adult, Kunming mice were included in this study. Learning and memory impairment was induced with an injection of 0.5 uL kainic acid （0.4 mg/mL） into the hippocampus. METHODS： The mice were randomized into three groups （n = 16）： model, control, and chlorogenic acid-treated. At 2 days following learning and memory impairment induction, intragastric administration of physiological saline or chlorogenic acid was performed in the model and chlorogenic acid-treated groups, respectively. The control mice were administered 0.5uL physiological saline into the hippocampus, and 2 days later, they received an intragastfic administration of physiological saline. Each mouse received two intragastric administrations （1 mL solution once） per day, for a total of 35 days. MAIN OUTCOME MEASURES： Detection of changes in hippocampal and cerebral cortical nNOS neurons by immunohistochemistry; determination of spatial learning and memory utilizing the Y-maze device. RESULTS： At day 7 and 35 after intervention, there was no significant difference in the number of nNOS-positive neurons in the cerebral cortex between the model, chlorogenic acid, and control groups （P 〉 0.05）. Compared with the control group, the number of nNOS-positive neurons in the hippocampal CA1-4 region was significantly less in the model group （P 〈 0.05）. However, the control group was not different from the chlorogenic acid-treated group （P 〉 0.05）. At day 7 following intervention, the number of correct responses in the Y-maze test was greater in the chlorogenic acid-treated group than in the model group. CONCLUSION： Chlorogenic acid protects kainic acid-induced injury to nNOS-positive neurons in the hippocampal CA1-4 regions, thereby ameliorating learning and memory impairment.

ONE PROBABLE MECHANISM OF THE LEARNING-MEMORY DAMAGE BY LEAD:THE CHANGES OF NOS IN HIPPOCAMPUS

Objective To study the effects of lead on the activity and expression of nitric oxide synthase (NOS) and relationship between the effects of lead on learning memory and changes of NOS in subfields of hippocampus. Methods Y maze test was used to study the effects of lead on ability of learning memory; NADPH d histochemistry and immunohistochemistry methods were used to investigate the changes of NOS in subfields of hippocampus. Results Compared with the control group, the ability of learning memory in lead exposed rats was significantly decreased ( P < 0.05 ); the number of NOS positive neurons in CA1 region and dentate gyrus of lead exposed rats was significantly decreased( P < 0.05 ), but no marked changes in CA3 region; the number of nNOS positive neurons in CA1 of lead exposed rats was also significantly decreased( P < 0.05 ), but no obvious changes in CA3. Conclusion Lead could damage the ability of learning memory in rats. Lead could decrease the activity and expression of NOS in hippocampus and had different effects on NOS in different subfields of hippocampus. The changes of NOS in hippocampus induced by lead may be the mechanism of the learning memory damage by lead.

Midazolam Impairs Learning and Memory Ability Through ERK/CREB Signaling Pathway and Oxidative Damage of Hippocampus in Rats

This study aimed to elucidate whether midazolam affected the learning and memory of rats through the extracellular signal-regulated kinase(ERK)/cyclic adenosine monophosphate response element-binding(CREB)signaling pathway and hippocampal oxidative damage.Overall 120 Wistar rats were randomly assigned to four groups,including one control and three midazolam-exposed groups(20,60 and 150 mg•kg^(-1)).After an intraperitoneal injection of midazolam/physiological saline for both 1 h(n=15)and 24 h(n=15),10 rats(five came from 1 h,and the remaining five came from 24 h)were randomly selected from each group for the Morris water maze test.The hippocampus tissue samples were harvested for the assessment of superoxide dismutase(SOD)and catalase(CAT)activities as well as glutathione peroxidase(GPx),malonyl dialdehyde(MDA),nitric oxide(NO)and inducible nitric oxide synthase(iNOS)levels.The remaining 80 rats were euthanized,and the hippocampal tissue was isolated.The expressions of ERK1,ERK2 and CREB mRNA were tested using RT-qPCR.The protein expressions of p-ERK1/2 and p-CREB were tested using Western blotting.The Morris water maze tests indicated that midazolam-treated rats have weaker learning and memory ability compared to the control rats.Midazolam increased MDA,NO,iNOS and CAT,and decreased GPx and SOD activities compared to the control group.The expression levels of ERK1/2 and CREB in the hippocampus of rats in the midazolam treatment groups were significantly lower compared to the control group at 1 h after intraperitoneal injection of midazolam,and in a dose-dependent relationship but returning it to normal levels at 24 h after midazolam intraperitoneal injection.Therefore,it was concluded that the learning and memory impairment of midazolam might be associated with the down-regulation of the ERK/CREB signaling pathway and oxidative damage in rat hippocampus.

有氧运动训练影响阿尔茨海默症小鼠海马Notch1、Caspase-3的表达

背景:β-淀粉样蛋白和Tau蛋白会对阿尔茨海默症患者的认知功能产生不良影响,研究发现Notch1及Caspase-3能够调控β-淀粉样蛋白和Tau蛋白的表达。Notch1及Caspase-3是否介导了有氧运动改善阿尔茨海默症患者认知能力的过程还不清楚,目前缺乏长期有氧运动影响阿尔茨海默症小鼠海马中Notch1及Caspase-3表达的研究。目的:观察长期有氧运动干预阿尔茨海默症小鼠的空间学习记忆情况及其海马中Notch1及Caspase-3的表达,探讨Notch1及Caspase-3对阿尔茨海默症小鼠的影响。方法:将3月龄野生型及APP/PS1双转基因阿尔茨海默症小鼠随机分为4组:野生对照组、野生运动组、阿尔茨海默症对照组、阿尔茨海默症运动组,每组20只。对照组小鼠不进行运动,运动组小鼠进行5个月的有氧运动干预。运动干预结束后,采用Morris水迷宫检测小鼠空间学习记忆能力;采用Real-timePCR、免疫荧光及Westernblot检测各组小鼠海马组织Aβ_(1-42)、Tau、Notch1及Caspase-3蛋白的表达。结果与结论:①阿尔茨海默症小鼠空间学习记忆能力显著差于野生组(P<0.05);运动组小鼠空间学习记忆能力显著优于对照组(P<0.05);②阿尔茨海默症对照组小鼠海马Aβ_(1-42)、Tau、Notch1及Caspase-3表达均显著高于野生对照组(P<0.05);阿尔茨海默症运动组小鼠海马Aβ_(1-42)、Tau、Notch1及Caspase-3表达显著低于阿尔茨海默症对照组(P<0.05);③提示:长期有氧运动干预能够改善阿尔茨海默症小鼠的空间学习记忆能力,而这可能与有氧运动降低阿尔茨海默症小鼠海马Notch1、Caspase-3、Aβ_(1-42)及Tau蛋白表达有关。

Quantitative proteomic and phosphoproteomic analyses of the hippocampus reveal the involvement of NMDAR1 signaling in repetitive mild traumatic brain injury

The cumulative damage caused by repetitive mild traumatic brain injury can cause long-term neurodegeneration leading to cognitive impairment.This cognitive impairment is thought to result specifically from damage to the hippocampus.In this study,we detected cognitive impairment in mice 6 weeks after repetitive mild traumatic brain injury using the novel object recognition test and the Morris water maze test.Immunofluorescence staining showed that p-tau expression was increased in the hippocampus after repetitive mild traumatic brain injury.Golgi staining showed a significant decrease in the total density of neuronal dendritic spines in the hippocampus,as well as in the density of mature dendritic spines.To investigate the specific molecular mechanisms underlying cognitive impairment due to hippocampal damage,we performed proteomic and phosphoproteomic analyses of the hippocampus with and without repetitive mild traumatic brain injury.The differentially expressed proteins were mainly enriched in inflammation,immunity,and coagulation,suggesting that non-neuronal cells are involved in the pathological changes that occur in the hippocampus in the chronic stage after repetitive mild traumatic brain injury.In contrast,differentially expressed phosphorylated proteins were mainly enriched in pathways related to neuronal function and structure,which is more consistent with neurodegeneration.We identified N-methyl-D-aspartate receptor 1 as a hub molecule involved in the response to repetitive mild traumatic brain injury,and western blotting showed that,while N-methyl-D-aspartate receptor 1 expression was not altered in the hippocampus after repetitive mild traumatic brain injury,its phosphorylation level was significantly increased,which is consistent with the omics results.Administration of GRP78608,an N-methyl-D-aspartate receptor 1 antagonist,to the hippocampus markedly improved repetitive mild traumatic brain injury-induced cognitive impairment.In conclusion,our findings suggest that N-methyl-D-aspartate receptor 1 signaling in the hippocampus is involved in cognitive impairment in the chronic stage after repetitive mild traumatic brain injury and may be a potential target for intervention and treatment.

Possible mechanisms of lycopene amelioration of learning and memory impairment in rats with vascular dementia

Oxidative stress is involved in the pathogenesis of vascular dementia. Studies have shown that lycopene can significantly inhibit oxidative stress;therefore, we hypothesized that lycopene can reduce the level of oxidative stress in vascular dementia. A vascular dementia model was established by permanent bilateral ligation of common carotid arteries. The dosage groups were treated with lycopene(50, 100 and 200 mg/kg) every other day for 2 months. Rats without bilateral carotid artery ligation were prepared as a sham group. To test the ability of learning and memory, the Morris water maze was used to detect the average escape latency and the change of search strategy. Hematoxylin-eosin staining was used to observe changes of hippocampal neurons. The levels of oxidative stress factors, superoxide dismutase and malondialdehyde, were measured in the hippocampus by biochemical detection. The levels of reactive oxygen species in the hippocampus were observed by dihydroethidium staining. The distribution and expression of oxidative stress related protein, neuron-restrictive silencer factor, in hippocampal neurons were detected by immunofluorescence histochemistry and western blot assays. After 2 months of drug administration,(1) in the model group, the average escape latency was longer than that of the sham group, and the proportion of straight and tend tactics was lower than that of the sham group, and the hippocampal neurons were irregularly arranged and the cytoplasm was hyperchromatic.(2) The levels of reactive oxygen species and malondialdehyde in the hippocampus of the model group rats were increased, and the activity of superoxide dismutase was decreased.(3) Lycopene(50, 100 and 200 mg/kg) intervention improved the above changes, and the lycopene 100 mg/kg group showed the most significant improvement effect.(4) Neuron-restrictive silencer factor expression in the hippocampus was lower in the sham group and the lycopene 100 mg/kg group than in the model group.(5) The above data indicate that lycopene 100 mg/kg could protect against the learning-memory ability impairment of vascular dementia rats. The protective mechanism was achieved by inhibiting oxidative stress in the hippocampus. The experiment was approved by the Animal Ethics Committee of Fujian Medical University, China(approval No. 2014-025) in June 2014.

Eleutheroside B or E enhances learning and memory in experimentally aged rats

Eleutheroside B or E, the main component of Acanthopanax, can relieve fatigue, enhance memory, and improve human cognition. Numerous studies have confirmed that high doses of acetylcholine significantly attenuate clinical symptoms and delay the progression of Alzheimer＇s disease. The present study replicated a rat model of aging induced by injecting quinolinic acid into the hippocampal CA1 region. These rats were intraperitoneally injected with low, medium and high doses of eleutheroside B or E （50, 100, 200 mg/kg）, and rats injected with Huperzine A or PBS were used as controls. At 4 weeks after administration, behavioral tests showed that the escape latencies and errors in searching for the platform in a Morris water maze were dose-dependently reduced in rats treated with medium and high-dose eleutheroside B or E. Hematoxylin-eosin staining showed that the number of surviving hippocampal neurons was greater and pathological injury was milder in three eleutheroside B or E groups compared with model group. Hippocampal homogenates showed enhanced cholinesterase activity, and dose-dependent increases in acetylcholine content and decreases in choline content following eleutheroside B or E treatment, similar to those seen in the Huperzine A group. These findings indicate that eleutheroside B or E improves learning and memory in aged rats. These effects of eleutheroside B or E may be mediated by activation of cholinesterase or enhanced reuse of choline to accelerate the synthesis of acetylcholine in hippocampal neurons.

Wendan decoction improves learning and memory deficits in a rat model of schizophrenia

An experimental model of schizophrenia was established using dizocilpine （MK-801）. Rats were intragastrically administered with Wendan decoction or clozapine for 21 days prior to establishing the model. The results revealed that the latency of schizophrenia model rats to escape from the hidden platform in the Morris water maze was significantly shortened after administration of Wendan decoction or clozapine. In addition, the treated rats crossed the platform significantly more times than the untreated model rats. Moreover, the rate of successful long-term potentiation induction in the Wendan decoction group and clozapine group were also obviously increased compared with the model group, and the population spike peak latency was significantly shortened. These experimental findings suggest that Wendan decoction can improve the learning and memory ability of schizophrenic rats to the same extent as clozapine treatment.

Effect of intrauterine hypoxia and Angelica sinensis injection on dentate gyrus neurons and learning and memory in juvenile rats

BACKGROUND： The present study analyzed the effect of 3 days （2 h/d） intrauterine hypoxia on learning and memory in juvenile rats, as well as the therapeutic effects of Angelica sinensis on dentate gyrus neurons, as well as learning and memory. OBJECTIVE： To explore the effects of intrauterine hypoxia on hippocampal dentate gyrus neurons, as well as learning and memory, in juvenile rats; to explore N-methyI-D-aspartate receptor-1 （NMDAR1） expression in the dentate gyrus of neonatal rats following intrauterine hypoxia, as well as prolonged hypoxia; to investigate the regulatory mechanisms of Angelica sinensis. DESIGN, TIME AND SETTING： A randomized and controlled experiment based on developmental neurobiology was performed at the Department of Histology and Embryology in Luzhou Medical College from October 2007 to October 2008. MATERIALS： Angelica sinensis solution （250 g/L） was obtained from Central South Hospital of Wuhan University, China. Neuron-specific enolase and NMDAR1 mRNA in situ hybridization reagents were provided by Wuhan Boster Biological Technology, China. Image-Pro Plus 6.0 analysis system was purchased from Media Cybernetics, USA. METHODS： Healthy pregnant Sprague Dawley rats （n = 30） were randomly divided into control （n = 10）, hypoxia （n = 10）, and Angelica （n = 10） groups. The Angelica and hypoxia pregnant rats were placed in a three-gas incubator （oxygen concentration： 13%） starting with day 14 of pregnancy for 2 hours/day for 5 consecutive days to establish a fetal rat intrauterine hypoxia model. One hour prior to modeling, the pregnant rats from the Angelica and hypoxia groups received Angelica sinensis and normal saline （8 mL/kg） injections, respectively, through the caudal vein. The control group procedures were identical to the hypoxia group, but lacked the hypoxic conditions. MAIN OUTCOME MEASURES： Brain tissues of neonatal rats were used to detect expression of NMDAR1 mRNA, and brain tissues of juvenile rats aged 30 days were used to determine neuron-specific enolase mRNA expression by in situ hybridization. Microscopic images （400x） of the hippocampal dentate gyrus were collected. The integral optical density （IOD） value of positive NMDAR1 mRNA cells in the dentate gyrus of neonatal rats, as well as the quantity and the IOD value of positive neuron-specific enolase mRNA cells in the dentate gyrus of juvenile rats, were analyzed with Image-Pro IPP6.0 software. At 30 days after birth, learning and memory parameters were measured in the juvenile rats using Morris water maze. RESULTS： The quantity and the IOD value of positive neuron-specific enolase mRNA cells in the dentate gyrus of the hypoxia group juvenile rats were significantly less than the control group （P 〈 0.05）, and also less than the Angelica group （P 〈 0.05）. The IOD value of positive NMDAR1 mRNA cells in the dentate gyrus of the hypoxia group neonatal rats was significantly greater than the control group, and also greater than the Angelica group （P 〈 0.05）. In the Morris water maze, the searching time during the probe trial and reversal probe trial was shorter in the hypoxia group juvenile rats compared with the control group, and the Angelica group was prolonged compared with the hypoxia group （P 〈 0.05）. CONCLUSION： Intrauterine hypoxia increased expression of NMDAR1 mRNA in the dentate gyrus of neonatal rats, reduced the number of dentate gyrus neurons, and negatively affected learning and memory in juvenile rats. In contrast, Angelica sinensis injection improved the intrauterine hypoxic condition, increased the number of dentate gyrus neurons, and improved the learning and memory deficits of the juvenile rats.