Rat Hippocampal Tissue Research Articles

Branch extension and subsequent migration of IB4 lectin-labeled MG in rat hippocampal tissue slices following application of exogenous ADP (1 mm): Movie 68_2.

Branch extension and subsequent migration of IB4 lectin-labeled MG in rat hippocampal tissue slices following application of exogenous ADP (1 mm): Movie 68_2.

Effects of Chinese herbal medicine Yinsiwei compound on spatial learning and memory ability and the ultrastructure of hippocampal neurons in a rat model of sporadic Alzheimer disease

To study the effects of Chinese herbal medicine Yinsiwei compound (YSW) on spatial learning and memory ability in rats with sporadic Alzheimer disease (SAD) and the ultrastructural basis of the hippocampal neurons. A rat model of SAD was established by intracerebroventricular injection of streptozotocin. The rats were divided into six groups: sham-operation group, model group, donepezil control group, and YSW low, medium and high dose groups. Drug interventions were started on the 21st day after modeling and each treatment group was given the corresponding drugs by gavage for two months. Meanwhile, the model group and the sham-operation group were given the same volume of distilled water by gavage once a day for two months. The Morris water maze was adopted to test spatial learning and memory ability of the rats. The place navigation test and the spatial probe test were conducted. The escape latency, total swimming distance and swimming time in the target quadrant of the rats were recorded. Also, the hippocampus tissues of rats were taken out and the ultrastructure of hippocampus neurons were observed by an electron microscope. In the place navigation test, compared with the model group, the mean escape latency and the total swimming distance of the donepezil group and the YSW low, medium and high dose groups were significantly shortened (P<0.05 or P<0.01). In the space probe test, the swimming time of each treatment group in the target quadrant was significantly longer than that of the model group (P<0.05 or P<0.01). For most of the test period, the donepezil group had no significant change compared with the YSW low, medium and high dose groups, respectively. The ultrastructure of the hippocampus neurons under the electron microscope also confirmed the efficacy of the drug treatment. Chinese herbal medicine YSW compound can improve spatial learning and memory impairment of rats with SAD. The ultrastructural basis may be that it can protect the microtubule structures of hippocampal neurons and prevent nerve axons from being damaged.

In vitro effects of neuropeptide Y in rat neocortical and hippocampal tissue

Neuropeptide Y (NPY) network effects in hippocampus and frontal cortex and its impact on epileptiform neocortical discharges were investigated in rat juvenile brain slices. NPY (1 μM) reduced amplitudes of paired pulse stimulation in hippocampal brain tissue ( p < 0.05) whereas NPY (1 nM–2 μM) had no effect in neocortex. Late stage epileptiform activity in the neocortex was unaffected by NPY (1 μM). Our results point to a region dependent effect of NPY with a high impact on hippocampal and minimal impact on neocortical networks.

Effect of Oral Resveratrol on the BDNF Gene Expression in the Hippocampus of the Rat Brain

Resveratrol is a plant polyphenolic compound. Evidence indicates that resveratrol has beneficial effects against aging and neurodegenerative diseases. The goal of our study was in vivo examination of the effects of resveratrol on the abundance of mRNA encoding Brain Derived Neurotrophic Factor (BDNF) in the hippocampus of rat brain. Rats were administrated orally by different doses (2.5-20mg/kg bwt) of resveratrol for 3, 10 and 30days. Saline was used as control and 10% ethanol in saline was used as vehicle for resveratrol. Measurement of BDNF mRNA by Real-time RT-PCR showed that levels of the mRNA for BDNF were significantly and dose dependently elevated in the hippocampal tissues of rats. The findings suggest that the neuroprotective effects of resveratrol may be at least partly due to its inducing effects on the expression levels of the BDNF mRNA.

In vitro assessment of the agonist properties of the novel 5-HT1A receptor ligand, CUMI-101 (MMP), in rat brain tissue

Development of agonist positron emission tomography (PET) radioligands for the 5-HT neurotransmitter system is an important target to enable the understanding of human 5-HT function in vivo. [(11)C]CUMI-101, proposed as the first 5-HT(1A) receptor agonist PET ligand, has been reported to behave as a potent 5-HT(1A) agonist in a cellular system stably expressing human recombinant 5-HT(1A) receptors. In this study, we investigate the agonist properties of CUMI-101 in rat brain tissue. [(35)S]-GTPγS binding studies were used to determine receptor function in HEK (human embryonic kidney) 293 cells transfected with human recombinant 5-HT(1A) receptors and in rat cortex and rat hippocampal tissue, following administration of CUMI-101 and standard 5-HT1A antagonists (5-HT, 5-CT and 8-OH-DPAT). CUMI-101 behaved as an agonist at human recombinant 5-HT(1A) receptors (pEC(50) 9.2). However, CUMI-101 did not show agonist activity in either rat cortex or hippocampus at concentrations up to 10 μM. In these tissues, CUMI-behaved as an antagonist with pK(B)s of 9.2 and 9.3, respectively. Our studies demonstrate that as opposed to its behavior in human recombinant system, in rat brain tissue CUMI-101 behaves as a potent 5-HT(1A) receptor antagonist.

Synapse Clusters Are Preferentially Formed by Synapses with Large Recycling Pool Sizes

Synapses are distributed heterogeneously in neural networks. The relationship between the spatial arrangement of synapses and an individual synapse's structural and functional features remains to be elucidated. Here, we examined the influence of the number of adjacent synapses on individual synaptic recycling pool sizes. When measuring the discharge of the styryl dye FM1–43 from electrically stimulated synapses in rat hippocampal tissue cultures, a strong positive correlation between the number of neighbouring synapses and recycling vesicle pool sizes was observed. Accordingly, vesicle-rich synapses were found to preferentially reside next to neighbours with large recycling pool sizes. Although these synapses with large recycling pool sizes were rare, they were densely arranged and thus exhibited a high amount of release per volume. To consolidate these findings, functional terminals were marked by live-cell antibody staining with anti-synaptotagmin-1-cypHer or overexpression of synaptopHluorin. Analysis of synapse distributions in these systems confirmed the results obtained with FM 1–43. Our findings support the idea that clustering of synapses with large recycling pool sizes is a distinct developmental feature of newly formed neural networks and may contribute to functional plasticity.

Flavan-3-ol compounds from wine wastes with in vitro and in vivo antioxidant activity.

It has been suggested that the dietary intake of antioxidant supplements could be a useful strategy to reduce the incidence of diseases associated with oxidative stress. The aim of present work is to study the possibility to obtain compounds with antioxidant activity from wine wastes using water as solvent. Results have shown that it is possible to obtain flavan-3-ol compounds from wine wastes both from V. vinifera (cv. Cabernet Sauvignon and Merlot) and V. labrusca (cv. Bordo and Isabella) species. The main phenolic compounds found in the extracts were catechin and epicatechin, followed by procyanidin B3, procyanidin B1, procyanidin B2, gallic acid, epigallocatechin, and procyanidin B4. All flavan-3-ol extracts showed significant in vitro and in vivo activities. It was found that the extracts were able to prevent lipid and protein oxidative damage in the cerebral cortex, cerebellum and hippocampus tissues of rats. Although further studies are necessary, these flavan-3-ol extracts show potential to be used to reduce the incidence of degenerative diseases associated with oxidative stress.

MicroRNA-101 Regulates Amyloid Precursor Protein Expression in Hippocampal Neurons

The amyloid precursor protein (APP) and its proteolytic product amyloid beta (Abeta) are associated with both familial and sporadic forms of Alzheimer disease (AD). Aberrant expression and function of microRNAs has been observed in AD. Here, we show that in rat hippocampal neurons cultured in vitro, the down-regulation of Argonaute-2, a key component of the RNA-induced silencing complex, produced an increase in APP levels. Using site-directed mutagenesis, a microRNA responsive element (RE) for miR-101 was identified in the 3'-untranslated region (UTR) of APP. The inhibition of endogenous miR-101 increased APP levels, whereas lentiviral-mediated miR-101 overexpression significantly reduced APP and Abeta load in hippocampal neurons. In addition, miR-101 contributed to the regulation of APP in response to the proinflammatory cytokine interleukin-1beta (IL-lbeta). Thus, miR-101 is a negative regulator of APP expression and affects the accumulation of Abeta, suggesting a possible role for miR-101 in neuropathological conditions.

Effect of levetiracetam on hippocampal protein expression and cell proliferation in rats

Levetiracetam (LEV) is a broad-spectrum antiepileptic drug (AED) with possibly also antiepileptogenic properties. LEV has a specific binding site in the central nervous system and reduces brain excitability; however, the precise mechanism of action (MOA) of LEV remains unclear. To further unravel the potential MOA pathways of LEV we investigated altered protein expression and cell proliferation in rat hippocampal tissue during LEV administration. On day 1 of the experiment, rats were randomly assigned to a treatment group (LEV, 600 mg/kg/day, n=10) and a control group (saline, n=10). On days 2 and 3 rats were injected with bromodeoxyuridine (50 mg/kg, i.p., BID). After 7 days of treatment rats were killed and their brains removed. The right hemisphere was processed for histochemistry. The left hippocampus was dissected and frozen for proteomic analysis. Proteins were extracted from the tissue and two-dimensional gel electrophoresis was performed. Treatment with LEV did not influence hippocampal cell proliferation. Multivariate analysis of differential protein expression, determined by proteomic analysis, revealed a significant clustering of control and treatment groups. The proteins which most contribute to the difference between groups were identified with mass spectrometry. The identified proteins were either involved in cytoskeleton, energy metabolism, neurotransmission, signal transduction, myelinization or stress response. LEV does not affect hippocampal cell proliferation but has significant effects on the expression of proteins involved in a variety of physiological processes involved in physiological processes that play an important role in the currently identified MOAs of AEDs such as neurotransmission and signal transduction.

Effects of Naoerkang on expressions of β-amyloid peptide 1-42 and neprilysin in hippocampus in a rat model of Alzheimer’s disease

To investigate the effects of Naoerkang (NEK), a compound traditional Chinese herbal medicine, on the expressions of beta-amyloid peptide 1-42 (Abeta(1-42)) and neprilysin (NEP) in hippocampal tissues in a rat model of Alzheimer's disease (AD). Forty-eight male SD rats were randomly divided into normal control group, untreated group, piracetam group, low-dose NEK group, medium-dose NEK group, and high-dose NEK group, with 8 rats in each group. Five microliters of Abeta(1-42) (2 microg/microL) were injected into CA1 area of hippocampus in rat to establish AD model whereas the normal control rats were injected with same volume of normal saline for comparison. The rats in the NEK groups were treated respectively with high-, medium- and low-dose [60, 30, 15 g/(kg.d)] NEK for 28 days consecutively; piracetam [0.375 g/(kg.d)] was intragastrically administered to rats in the piracetam group; and normal saline was applied in the control and untreated groups. Y-maze test was used for behavioral study to test the learning and memory abilities of rats in different groups. The expressions of Abeta(1-42) and NEP in hippocampus were determined by immunohistochemical method, and the results were analyzed by image acquisition and analysis system. Injection of Abeta(1-42) could induce learning and memory dysfunction and up-regulate Abeta(1-42) expression in hippocampal tissue in rats of the untreated group. Compared with the normal control group, the abilities of learning and memory of rats in the untreated group were significantly decreased (P<0.01) and the expression of Abeta(1-42) was significantly increased (P<0.01) after model establishment. After 28-day administration of NEK and piracetam, the abilities of learning and memory of AD rats in piracetam and low-dose, medium-dose and high-dose NEK groups were significantly improved as compared with the untreated group (P<0.01 or P<0.05); the expression of Abeta(1-42) in hippocampal tissues was decreased (P<0.01 or P<0.05) and the expression of NEP was increased (P<0.01 or P<0.05), especially in the high-dose NEK group. NEK can play the role of anti-dementia by increasing the expression of NEP in hippocampal tissues of AD rats so as to reduce the quantity of AAbeta(1-42) and by improving the ability of learning and memory of rats with AD.

Diabetes alters aromatase enzyme levels in sciatic nerve and hippocampus tissues of rats.

Diabetes mellitus (DM) is associated with increased risk of impaired cognitive function. Diabetic neuropathy is one of the most common and important complications of DM. Estrogens prevent neuronal loss in experimental models of neurodegeneration and accelerate nerve regeneration. Aromatase catalyzes the conversion of androgens to estrogens and expressed in a variety of tissues including neurons. Although insulin is known to regulate the activity of aromatase there is no study about the effects of diabetes on this enzyme. Present study was designed to investigate the effects of experimental diabetes on aromatase expression in nervous system. Gender-based differences were also investigated. Rats were injected with streptozotocin to induce diabetes. At the end of 4 and 12 weeks sciatic nerve and hippocampus homogenates were prepared and evaluated for aromatase proteins. Aromatase expressions in sciatic nerves of both genders were decreased in 4 weeks of diabetes, but in 12 weeks the enzyme levels were increased in females and reached to control levels in male animals. Aromatase levels were not altered in hippocampus at 4 weeks but increased at 12 weeks in female diabetic rats. No significant differences were observed at enzyme levels of hippocampus in male diabetic rats. Insulin therapy prevented all diabetes-induced changes. In conclusion, these results indicated for the first time that, DM altered the expression of aromatase both in central and peripheral nervous systems. Peripheral nervous system is more vulnerable to damage than central nervous system in diabetes. These effects of diabetes differ with gender and compensatory neuroprotective mechanisms are more efficient in female rats.

Periodic fasting alters neuronal excitability in rat neocortical and hippocampal tissues

Dietary restriction has been shown to be associated with marked changes in brain function. Periodic fasting was suggested to be beneficial in reducing both the incidence and severity of some neurological disorders. The aim of this investigation was to study the effect of periodic fasting on the neuronal network excitability in the neocortex and hippocampus and its possible influence on the brain under pathological conditions. Direct current (DC) recordings in the somatosensory neocortex of fasting rats (15 h water and food deprivation per day) during drinking revealed a negative potential shift. Using voltage sensitive dye imaging and tetanus-induced long-term potentiation (LTP) in ex vivo/ in vitro experiments, neuronal network activities as well as synaptic efficacy were investigated in rat neocortical and hippocampal slices after 4 weeks of periodic fasting. Stimulus-induced patterns of bioelectric activity showed enhanced neuronal network excitability in the neocortex and decreased bioelectric activity in the hippocampus. LTP was significantly increased in neocortical slices and inhibited in hippocampal tissues. Both hippocampal and neocortical tissues exhibited a higher tolerance to hypoxic stress but not to 0-Mg 2+-eliciting epileptiform field potentials. Neocortical slices also exhibited a higher threshold for the initiation of spreading depression. These experiments indicate that repetitive DC potential shifts occurring in fasting rats change the pattern of bioelectrical activities in cortical and subcortical regions. Through these alterations, the neocortex and hippocampus may become tuned for the efficient regulation of consummatory behaviour.

An in-silico model of the biosynthesis of neurotransmitter glutamate, elucidates the complex regulatory role of glucocorticoids in neurotransmitter glutamate release

An in-silico model, of the glucocorticoid regulated glutamate release, in rat hippocampal tissue, is constructed. The model permits the pseudo-steady state estimation of various fluxes, experimentally impossible to measure, from a set of measured rates. Estimates of the astrocytic pyruvate carboxylase reaction and the neuronal TCA cycle rates are correlated with different dexamethasone concentrations, in order to extrapolate explicit kinetic equations. The model suggests that the observed effects of glucocorticoids can be attributed to the inhibitory actions of dexamethasone on two competing pathways, that of the neuronal TCA cycle and the biosynthetic pathway of neurotransmitter glutamate.

SGK1 Phosphorylation of IκB Kinase α and p300 Up-regulates NF-κB Activity and Increases N-Methyl-D-aspartate Receptor NR2A and NR2B Expression

Serum- and glucocorticoid-inducible kinase 1 (SGK1) is a downstream target of phosphatidylinositol 3-kinase signaling, and it regulates various cellular and physiological functions, but the SGK1 substrate proteins and genes regulated by SGK1 are less known. Here we have identified IkappaB kinase alpha (IKKalpha) as a novel substrate of SGK1 by using biochemical and bioinformatic approaches. SGK1 directly phosphorylates IKKalpha at Thr-23 and indirectly activates IKKalpha at Ser-180. Furthermore, SGK1 enhanced nuclear factor kappaB (NF-kappaB) activity and up-regulated N-methyl-d-aspartate receptor NR2A and NR2B expression through activation of IKKalpha at Thr-23 and Ser-180, and these two residues play an equally important role in mediating these effects of SGK1. Although SGK1 does not phosphorylate IKKbeta, IKKbeta activity is still required for IKK complex activation and for SGK1 phosphorylation and activation of NF-kappaB. In addition, SGK1 increased the acetylation of NF-kappaB through phosphorylation of p300 at Ser-1834, and this also leads to NF-kappaB activation and NR2A and NR2B expression. Moreover, an endogenous stimulus of SGK1, insulin, increased IKKalpha and NF-kappaB phosphorylation as well as NF-kappaB acetylation and NF-kappaB activity, but SGK1 small interfering RNA transfection blocked these effects of insulin. In examination of the functional significance of the SGK1-IKKalpha-NF-kappaB signaling pathway, we found that transfection of the IKKalpha double mutant (IKKalphaT23A/S180A) to rat hippocampus antagonized SGK-1-mediated spatial memory facilitation. Our results together demonstrated novel substrate proteins of SGK1 and novel SGK1 signaling pathways. Activation of these signaling pathways enhances NR2A and NR2B expression that is implicated in neuronal plasticity.

Different regional neuroinhibitory effects of adenosine on stimulus-induced patterns of bioelectric activity of rat hippocampal and neocortical tissues

Adenosine is an inhibitory modulator of brain activity with neuroprotective and anticonvulsant properties. To investigate the distribution of bioelectric activities under application of adenosine, rat hippocampal and neocortical slices were incubated with the voltage-sensitive dye RH795 and neuronal activity was monitored using a fast-imaging photodiode array combined with standard field potential recordings. The effects of adenosine (1–50 μmol/l) on the spatial distribution of stimulus-induced activities were studied in non-epileptiform as well as epileptiform conditions. Epileptiform activity was induced by omission of Mg2+ from the bath medium. The adenosine’s inhibitory effects on the amplitude and spatial extent of stimulus-induced bioelectric activity in the hippocampus were most prominent in strata radiatum and pyramidale in both control and epileptic mediums. Adenosine’s inhibitory actions were different on various layers of neocortical tissues in non-epileptiform and epileptiform conditions. Layers II and III showed the most inhibition by application of adenosine in control slices. In epileptiform medium, however, adenosine exerts significant suppressive effects only in layer I of neocortical slices. The data demonstrate a region-specific modulatory potential of adenosine on neuronal network excitability in the hippocampus and neocortex. This may be important in local adenosine therapy in epilepsy.

Lack of P2X receptor mediated currents in astrocytes and GluR type glial cells of the hippocampal CA1 region

Purinergic signalling plays a major role in intercellular communication between neurons and glial cells. Glial cells express metabotropic receptors for ATP and adenosine, the latter being activated after ATP cleavage through extracellular ecto-ATPase activity. Ionotropic receptors for extracellular ATP, so called P2X receptors, might contribute to neuron-glia signalling. However, experimental evidence for the presence of these receptors in glial cells is less convincing so far. In a previous study, immunohistochemistry was used to identify P2X(1-4,6,7) receptor protein in S100beta-positive hippocampal glial cells. Applying patch clamp and fast application techniques, here we challenged the question of the functional expression of these receptors. Time correlated membrane currents served as test criterion for receptor function, since P2X receptor activation leads to the opening of unspecific cation channels in a millisecond time scale. Agonists were applied via short pressure puffs, with a fast concentration clamp method and through UV flash triggered photolysis of caged ATP. Two types of murine hippocampal macroglial cells, both labelled by the expression of green fluorescence protein driven by the human glial fibrillary acid protein promoter, were analysed in acute brain slices and in freshly dissociated cell suspensions. Surprisingly, ATP or related agonists completely failed to activate currents. Additionally, changes in spontaneously occurring glial postsynaptic currents were never observed. These results have been verified using rat and human hippocampal tissue as well as investigating cells from P2X7 knock out mice. It is concluded that in acute preparations, astroglial cells of the hippocampal CA1 subfield do not express functional P2X receptors.

Wnt pathway in the formation of ischemic brain injury*: Interventional pathway of basic fibroblast growth factor

Background Basic fibroblast growth factor (bFGF) can reduce neuronal apoptosis following ischemia/reperfusion (I/R) injury. Mechanism of the phenomenon should be elucidated. Objective The goal of this study was to observe the effect of bFGF on the expressions of Dickkopf-1(DKK-1) and β-catenin in the Wnt pathway in hippocampal tissue of rats following brain I/R injury, in order to investigate the role of Wnt pathway in the formation of ischemic brain injury. Design Randomized controlled experiment. Setting Shenyang Medical College. Materials Thirty healthy 3 months old male Wistar rats, weighing 300–350 g, were provided by the Experimental Animal Center of Shenyang Medical College. Thirty rats were randomized into sham-operation group, model group and treatment group. Goat anti-rat monoclonal antibody β-catenin was purchased from SANTA CRUZ Company. BFGF was developed by Beijing SL Pharmaceutical Co., Ltd. Methods This experiment was carried out in the Shenyang Medical College between November 2005 and May 2006. ▪ Focal brain I/R by suture-occluded method was modeled in rats in the treatment group and model group. Their middle cerebral artery was occluded 1 hour and reperfused for 24 hours. While in the sham-operation group, only the right common carotid artery and external carotid artery of rats were occluded for 90 minutes. ▪ The rats in the treatment group were intraperitoneally injected with 10 μ/kg bFGF, and those in the other groups were intraperitoneally injected with the same amount of saline. Main outcome measures Following I/R 48 hours, the expressions of β-catenin and Dickkopf-1 mRNA in the neurons of hippocampal CA1 region by immunohistochemical SABC and RT-PCR. Results Following I/R 48 hours, the expressions of β-catenin and Dickkopf-1 mRNA in the neurons of hippocampal CA1 region was evaluated by means of immunohistochemical SABC and RT-PCR. ▪ Expression of DKK-1 mRNA in the sham-operation group was at low level, it was significantly higher in the model group compared to the sham-operation group; Expression of DKK-1 mRNA in the treatment group was significantly lower than that in the model group. ▪ Expression of β-catenin in the cerebral cortex and hippocampal cytoplasm of rats: The mean gray scale of β-catenin of model group was significantly lower than that of sham-operation group (74.27±2.65 vs. 111.36±5.39, P < 0.05); The mean gray scale of β-catenin of treatment group was significantly higher than that of model group (86.18±7.41 vs. 74.27±2.65, P < 0.05). Conclusion bFGF may influence Wnt pathway by participating in the regulation of DKK-1 mRNA and β-catenin expressions, and thereby protect neurons.

Evidence against enhanced glutamate transport in the anticonvulsant mechanism of the ketogenic diet

Excessive glutamatergic neurotransmission is considered an underlying factor of epilepsy. Energy-dependent glutamate transporters clear extracellular glutamate to limit neuronal excitability. Evidence suggests that reduced expression and/or activity of glutamate transporters contribute to hyperexcitability and progressive seizure activity in rats. By comparison, treatment with the anticonvulsant ketogenic diet (KD) results in increased mRNA expression of the neuronal glutamate transporter EAAC1, elevated energy reserves, and an increased resistance to seizures in rats. The goal of the current study was to determine whether the expression and/or re-uptake activity of glutamate transporters were elevated in hippocampal tissue of rats after KD treatment. Rats were fed either a ketogenic- or control diet for 4-5 weeks. Western blot analysis showed that protein levels of EAAC1, GLT-1 and GLAST glutamate transporters were not changed in hippocampus, cerebral cortex, or cerebellum after KD. Electron microscopic evidence indicated that the KD did not affect hippocampal EAAC1 distribution. In addition, the re-uptake activity of (3)H-glutamate into hippocampal proteoliposomes was similar in both KD and control tissue extracts. These multiple studies suggest that the anticonvulsant nature of the KD does not stem from enhanced glutamate re-uptake.

Suppressive Effects of Melatonin on Amyloid-β-induced Glial Activation in Rat Hippocampus

Growing evidence indicates that activated glia, as a result of chronic inflammation, are associated with amyloid-beta peptide (Abeta) deposits in the brain of Alzheimer's disease (AD) patients. The purpose of the present study was to investigate, in vivo, the effects of melatonin on glia activation, which may contribute to improved learning and memory in amnesic rats induced by amyloid-beta peptide 25-35 (Abeta25-35). We examined cognitive function using the Morris water maze test. Expression of interleukin 1alpha (IL-1alpha) or complement 1q (C1q) in rat hippocampal tissue was determined by immunohistochemistry. It was found that Abeta25-35 injected into rat hippocampus induced an impairment in learning and memory and a marked increase of positive glial cells expressing IL-1alpha and C1q in hippocampus, compared with the controls. This suggests that glial activation triggered by Abeta25-35 parallels the dysfunction of learning and memory. Melatonin, at doses of 0.01, 0.1, and 1 mg/kg (i.g. for 10 days), improved learning and memory of rats treated with Abeta25-35. Cells expressing IL-1alpha and C1q were significantly decreased in hippocampus by pretreatment with melatonin at doses of 0.1 mg/kg and 1 mg/kg, but not at the dose of 0.01 mg/kg. Our data indicate that melatonin inhibited expressions of proinflammatory factors, which may contribute to improvement of learning and memory function in AD.

Interleukin-1β Released by gp120 Drives Neural Death through Tyrosine Phosphorylation and Trafficking of NMDA Receptors

Interleukin-1beta is a proinflammatory cytokine implicated under pathological conditions involving NMDA receptor activation, including the AIDS dementia complex (HAD). No information is available on the molecular mechanisms recruited by native interleukin-1beta produced under this type of condition. Using a sandwich co-culture of primary hippocampal neurons and glia, we investigated whether native interleukin-1beta released by HIV-gp120-activated glia (i) affects NMDAR functions and (ii) the relevance on neuronal spine density and survival, two specific traits of HAD. Increased phosphorylation of NR2B Tyr-1472 was observed after 24 h of exposure of neurons to 600 pm gp120. This effect occurred only when neurons were treated in the presence of glial cells and was abolished by the interleukin-1 receptor antagonist (IL-1ra). Gp120-induced phosphorylation of NR2B resulted in a sustained elevation of intracellular Ca(2+) in neurons and in a significant increase of NR2B binding to PSD95. Increased intracellular Ca(2+) was prevented by 10 mum ifenprodil, that selectively inhibits receptors containing the NR2B, by interleukin-1ra and by Ca-pYEEIE, a Src family SH2 inhibitor peptide. These last two inhibitors, prevented also NR2B binding to PSD95. Finally, gp120 reduced by 35% of the total PSD95 positive spine density after 48 h of treatment and induced by 30% of the neuronal death. Again, both of these effects were blocked by Ca-pYEEIE. Altogether, our data show that gp120 releasing interleukin-1beta from glia increases tyrosine phosphorylation of NMDAR. Thus, tyrosine phosphorylation may contribute to the sensitization of the receptor increasing its function and synaptic localization. Both of these effects are relevant for neurodegeneration.