Hippocampal Neuronal Model Research Articles

TGF-β1 protection against Aβ1-42-induced hippocampal neuronal inflammation and apoptosis by TβR-I.

Alzheimer's disease (AD), the most common chronic neurodegenerative disease, is pathologically characterized by the formation of neurofibrillary tangles because of hyperphosphorylation of tau protein and extracellular deposits of amyloid-β (Aβ) protein termed senile plaques. Recent studies indicate that neuronal apoptosis caused by chronic neuroinflammation is one of the important pathogenesis of AD. Transforming growth factor (TGF)-β1 is a pleiotropic cytokine with immunosuppressive and anti-inflammatory properties. However, it is poorly known whether the anti-inflammatory property of TGF-β1 is involved in a neuroprotection in AD. Here, an AD cell model of hippocampal neurons induced by Aβ1-42 was used to show an anti-inflammatory and neuroprotective effect of TGF-β1 through its receptor transforming growth factor-β receptor type I (TβR-I). As expected, Aβ1-42-induced an upregulation in neuronal expression of amyloid precursor protein (APP), tumor necrosis factor-α, cyclooxygenase-2, Bax, cleaved caspase-3, and cleaved caspase-9, and a downregulation in the expression of Bcl-2, as well as an increase in the number of NeuN/terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate-biotin nick end labeling (TUNEL) double-positive cells. TGF-β1 pretreatment reduced the Aβ1-42-induced effects of upregulating APP, tumor necrosis factor-α, Bax, cleaved caspase-3 and cleaved caspase-9, and downregulating Bcl-2, in addition to increasing NeuNTUNEL cell number. TβR-I expression in hippocampal neurons was downregulated by Aβ1-42 exposure, but upregulated by TGF-β1 pretreatment. Silencing of the TβR-I gene in the neurons abolished the anti-inflammatory and antiapoptotic effects of TGF-β1 in the Aβ1-42-induced AD cell model. These findings suggest that TGF-β1 protects neurons against Aβ1-42-induced neuronal inflammation and apoptosis by activation of TβR-I.

Multiple Actions of Rotenone, an Inhibitor of Mitochondrial Respiratory Chain, on Ionic Currents and Miniature End-Plate Potential in Mouse Hippocampal (mHippoE-14) Neurons

Background/Aims: Rotenone (Rot) is known to suppress the activity of complex I in the mitochondrial chain reaction; however, whether this compound has effects on ion currents in neurons remains largely unexplored. Methods: With the aid of patch-clamp technology and simulation modeling, the effects of Rot on membrane ion currents present in mHippoE-14 cells were investigated. Results: Addition of Rot produced an inhibitory action on the peak amplitude of I_Na with an IC₅₀ value of 39.3 µM; however, neither activation nor inactivation kinetics of I_Na was changed during cell exposure to this compound. Addition of Rot produced little or no modifications in the steady-state inactivation curve of I_Na. Rot increased the amplitude of Ca²⁺-activated Cl^- current in response to membrane depolarization with an EC₅₀ value of 35.4 µM; further addition of niflumic acid reversed Rot-mediated stimulation of this current. Moreover, when these cells were exposed to 10 µM Rot, a specific population of ATP-sensitive K⁺ channels with a single-channel conductance of 18.1 pS was measured, despite its inability to alter single-channel conductance. Under current clamp condition, the frequency of miniature end-plate potentials in mHippoE-14 cells was significantly raised in the presence of Rot (10 µM) with no changes in their amplitude and time course of rise and decay. In simulated model of hippocampal neurons incorporated with chemical autaptic connection, increased autaptic strength to mimic the action of Rot was noted to change the bursting pattern with emergence of subthreshold potentials. Conclusions: The Rot effects presented herein might exert a significant action on functional activities of hippocampal neurons occurring in vivo.

Trafficking patterns of NMDA and GABAA receptors in a Mg2+-free cultured hippocampal neuron model of status epilepticus

An altered pattern of receptor trafficking is one of the pathophysiologic mechanisms of status epilepticus (SE). The gradual internalization of GABAA receptors (GABARs) occurs in both in vitro and in vivo models of SE and is thought to be a cause of decreased GABAergic inhibition. Unlike GABARs, little is known about alterations in NMDA receptor (NMDAR) trafficking during SE, even though increased activity of NMDARs is indispensable for the induction and maintenance of SE. Therefore, we aimed to simultaneously investigate the changes in the trafficking patterns of GABARs and NMDARs in an in vitro cultured hippocampal neuron model of SE. For induction of epileptiform discharges, hippocampal neurons were exposed to external medium without Mg2+. Biotinylation assay and immunofluorescence staining for GABAR β2,3 and NMDAR NR1 subunits were performed to quantify and visualize surface GABARs and NMDARs, respectively. The frequency of spontaneous action potentials increased more than 4-fold after Mg2+-free induction. The level of surface GABARs decreased over time after Mg2+-free induction, dropping to approximately 50% of control levels an hour after Mg2+-free induction. By contrast, the trafficking of NMDARs to the surface was enhanced after a slight time lag, increasing by 30% of control levels an hour after Mg2+-free induction. Our data showed the changes of both NMDAR and GABAR trafficking during prolonged SE induced by a Mg2+-free extracellular environment and confirmed that this in vitro SE model is suitable for examining alterations in the receptor trafficking pattern by prolonged seizure activity. These results suggest that targeting of surface NMDAR could be a promising method in controlling benzodiazepine-resistant SE.

Effect of propofol on mitochondrial fission in a rat hippocampal neuron model of hypoxia/reoxygenation injury

Objective To evaluate the effect of propofol on mitochondrial fission in a rat hippocampal neuron model of hypoxia/reoxygenation (H/R) injury. Methods Primarily cultured hippocampal neurons of neonatal Sprague-Dawley rats were randomly divided into 4 groups (n= 42 each) using a random number table: control group (group C); vehicle group (group V); H/R group; H/R+ propofol group (group H/R+ P). In group V, H/R was not produced, the vehicle dimethyl sulfoxide with the final concentration of 0.01% was added, and the cells were then incubated for 6 h. In group H/R, the hippocampal neurons were subjected to oxygen-glucose deprivation for 6 h followed by 20 h reoxygenation.In group H/R+ P, propofol with the final concentration of 1 μmol/L was added at 6 h of hypoxia.At 20 h of reoxygenation, the cell apoptosis (using flow cytometry), Ca2+ concentrations in cytoplasm (with the laser scanning confocal microscope), calcineurin (CaN) activities (by enzyme-linked immunosorbent assay), and expression of mitochondrial fission proteins dynamin-related protein 1 (Drp1) and fission 1 (Fis1), and apoptosis-related proteins cytochrome c (Cyt c) and apoptosis-inducing factor (AIF) (by Western blot) were measured.The apoptotic rate was calculated. Results Compared with group C, the apoptotic rate, Ca2+ concentrations, CaN activities, and expression of Drp1, Fis1, Cyt c and AIF were significantly increased in H/R and H/R+ P groups (P 0.05). Compared with group H/R, the apoptotic rate, Ca2+ concentrations, CaN activities, and expression of Drp1, Fis1, Cyt c and AIF were significantly decreased in group H/R+ P (P<0.05=. Conclusion Propofol can reduce the H/R injury to rat hippocampal neurons through inhibiting mitochondrial fission. Key words: Propofol; Anoxia; Mitochondria; Hippocampus; Neurons

Mathematical Modeling in Neuroscience: Neuronal Activity and Its Modulation by Astrocytes.

Mathematical Modeling in Neuroscience: Neuronal Activity and Its Modulation by Astrocytes.

ON THE CELLULAR MECHANISMS UNDERLYING WORKING MEMORY CAPACITY IN HUMANS

The cellular processes underlying individual differences in the Working Memory Capacity (WMC) of humans are essentially unknown. Psychological experiments suggest that subjects with lower working memory capacity (LWMC), with respect to subjects with higher capacity (HWMC), take more time to recall items from a list because they search through a larger set of items and are much more susceptible to interference during retrieval. However, a more precise link between psychological experiments and cellular properties is lacking and very difficult to investigate experimentally. In this paper, we investigate the possible underlying mechanisms at the single neuron level by using a computational model of hippocampal CA1 pyramidal neurons, which have been suggested to be deeply involved in the recognition of specic items. The model makes a few experimentally testable predictions on the cellular processes underlying the cumulative latency in delayed free recall experimentally observed in humans under different testing conditions. The results suggest, for the rst time, a physiologically plausible explanation for individual performances, and establish a proof of principle for the hypothesis that HWMC individuals use a larger portion of the apical tree with a correlated higher level of synaptic background noise.

Toward dissecting the etiology of schizophrenia: HDAC1 and DAXX regulate GAD67 expression in an in vitro hippocampal GABA neuron model.

Schizophrenia (SZ) is associated with GABA neuron dysfunction in the hippocampus, particularly the stratum oriens of sector CA3/2. A gene expression profile analysis of human postmortem hippocampal tissue followed by a network association analysis had shown a number of genes differentially regulated in SZ, including the epigenetic factors HDAC1 and DAXX. To characterize the contribution of these factors to the developmental perturbation hypothesized to underlie SZ, lentiviral vectors carrying short hairpin RNA interference (shRNAi) for HDAC1 and DAXX were used. In the hippocampal GABA neuron culture model, HiB5, transduction with HDAC1 shRNAi showed a 40% inhibition of HDAC1 mRNA and a 60% inhibition of HDAC1 protein. GAD67, a enzyme associated with GABA synthesis, was increased twofold (mRNA); the protein showed a 35% increase. The expression of DAXX, a co-repressor of HDAC1, was not influenced by HDAC1 inhibition. Transduction of HiB5 cells with DAXX shRNAi resulted in a 30% inhibition of DAXX mRNA that translated into a 90% inhibition of DAXX protein. GAD1 mRNA was upregulated fourfold, while its protein increased by ~30%. HDAC1 expression was not altered by inhibition of DAXX. However, a physical interaction between HDAC1 and DAXX was demonstrated by co-immunoprecipitation. Inhibition of HDAC1 or DAXX increased expression of egr-1, transcription factor that had previously been shown to regulate the GAD67 promoter. Our in vitro results point to a key role of both HDAC1 and DAXX in the regulation of GAD67 in GABAergic HiB5 cells, strongly suggesting that these epigenetic/transcription factors contribute to mechanisms underlying GABA cell dysfunction in SZ.

Gestational Hypothyroxinemia Affects Glutamatergic Synaptic Protein Distribution and Neuronal Plasticity Through Neuron-Astrocyte Interplay

Gestational hypothyroxinemia, characterized by low levels of maternal thyroxine (T4) during gestation, is closely associated with cognitive impairment in offspring. Studies in animal models have shown that this condition alters neuronal glutamatergic synapses in the hippocampus. Given that astrocytes critically contribute to the establishment and functioning of synapses, the aim of this study was to determine the effects of gestational hypothyroxinemia on the capacity of astrocytes to regulate glutamatergic synapses. In an in vitro co-culture model of astrocytes and hippocampal neurons, gestational hypothyroxinemia profoundly affected the synaptic patterns of GluN1 and CD3ζ in an astrocyte-dependent manner. These effects were associated with impaired plasticity that was dependent on both neuronal and astrocyte contributions. These results highlight the importance of neuron-astrocyte interplay in the deleterious effects of gestational hypothyroxinemia and the timely diagnosis and treatment of this condition during gestation to ensure proper central nervous system development in offspring.

Induction of long-term potentiation and depression in individual synapses of CA1 pyramidal neurons

Long-Term Potentiation (LTP) and Depression (LTD), the two major forms of long-lasting synaptic plasticity in the mammalian neurons, represent a basic step to understand neuronal development, circuit reorganization, learning and memory mechanisms. Experimental studies on LTP and LTD are usually performed using in vitro or in vivo preparations, exploiting repetitive and properly patterned stimulation protocols to induce long-lasting changes in the strength of a synaptic connection. Although the underlying molecular mechanisms are starting to be unraveled and are under intense experimental and theoretical scrutiny, especially in the CA1 region of the hippocampus, experimenters often report problems in using standard induction protocols to obtain consistent results, especially for LTD in vivo. We hypothesize that a possible source of confusion in interpreting the results, from any given experiment on synaptic plasticity, can be the intrinsic limitation of the experimental techniques, which cannot take into account the actual state and peak conductance of the synapses before the conditioning protocol. Within this context, using biophysical models of synaptic plasticity and hippocampal CA1 pyramidal neurons, we investigate the relation between what is observed at the soma and LTP/LTD induction patterns, pre-conditioning synaptic strength, and dendritic location. Our model and the results pointed out that the outcome of an experiment, testing the amount of synaptic LTP/LTD plasticity that can be induced, strongly depends at least on the initial synaptic state and peak conductance. In addition, the model explains why LTD induction may be more critical to be obtained, with respect to LTP, especially in vivo, and suggests experimentally testable predictions on the stimulation protocols that may be more effective.

Variability in State-Dependent Plasticity of Intrinsic Properties during Cell-Autonomous Self-Regulation of Calcium Homeostasis in Hippocampal Model Neurons

How do neurons reconcile the maintenance of calcium homeostasis with perpetual switches in patterns of afferent activity? Here, we assessed state-dependent evolution of calcium homeostasis in a population of hippocampal pyramidal neuron models, through an adaptation of a recent study on stomatogastric ganglion neurons. Calcium homeostasis was set to emerge through cell-autonomous updates to 12 ionic conductances, responding to different types of synaptically driven afferent activity. We first assessed the impact of theta-frequency inputs on the evolution of ionic conductances toward maintenance of calcium homeostasis. Although calcium homeostasis emerged efficaciously across all models in the population, disparate changes in ionic conductances that mediated this emergence resulted in variable plasticity to several intrinsic properties, also manifesting as significant differences in firing responses across models. Assessing the sensitivity of this form of plasticity, we noted that intrinsic neuronal properties and the firing response were sensitive to the target calcium concentration and to the strength and frequency of afferent activity. Next, we studied the evolution of calcium homeostasis when afferent activity was switched, in different temporal sequences, between two behaviorally distinct types of activity: theta-frequency inputs and sharp-wave ripples riding on largely silent periods. We found that the conductance values, intrinsic properties, and firing response of neurons exhibited differential robustness to an intervening switch in the type of afferent activity. These results unveil critical dissociations between different forms of homeostasis, and call for a systematic evaluation of the impact of state-dependent switches in afferent activity on neuronal intrinsic properties during neural coding and homeostasis.

Effect of the Initial Synaptic State on the Probability to Induce Long-Term Potentiation and Depression

Long-term potentiation (LTP) and long-term depression (LTD) are the two major forms of long-lasting synaptic plasticity in the mammalian neurons, and are directly related to higher brain functions such as learning and memory. Experimentally, they are characterized by a change in the strength of a synaptic connection induced by repetitive and properly patterned stimulation protocols. Although many important details of the molecular events leading to LTP and LTD are known, experimenters often report problems in using standard induction protocols to obtain consistent results, especially for LTD in vivo. We hypothesize that a possible source of confusion in interpreting the results, from any given experiment on synaptic plasticity, can be the intrinsic limitation of the experimental techniques, which cannot take into account the actual state and peak conductance of the synapses before the conditioning protocol. In this article, we investigate the possibility that the same experimental protocol may result in different consequences (e.g., LTD instead of LTP), according to the initial conditions of the stimulated synapses, and can generate confusing results. Using biophysical models of synaptic plasticity and hippocampal CA1 pyramidal neurons, we study how, why, and to what extent the phenomena observed at the soma after induction of LTP/LTD reflects the actual (local) synaptic state. The model and the results suggest a physiologically plausible explanation for why LTD induction is experimentally difficult to obtain. They also suggest experimentally testable predictions on the stimulation protocols that may be more effective.

Dendritic atrophy constricts functional maps in resonance and impedance properties of hippocampal model neurons.

A gradient in the density of hyperpolarization-activated cyclic-nucleotide gated (HCN) channels is necessary for the emergence of several functional maps within hippocampal pyramidal neurons. Here, we systematically analyzed the impact of dendritic atrophy on nine such functional maps, related to input resistance and local/transfer impedance properties, using conductance-based models of hippocampal pyramidal neurons. We introduced progressive dendritic atrophy in a CA1 pyramidal neuron reconstruction through a pruning algorithm, measured all functional maps in each pruned reconstruction, and arrived at functional forms for the dependence of underlying measurements on dendritic length. We found that, across frequencies, atrophied neurons responded with higher efficiency to incoming inputs, and the transfer of signals across the dendritic tree was more effective in an atrophied reconstruction. Importantly, despite the presence of identical HCN-channel density gradients, spatial gradients in input resistance, local/transfer resonance frequencies and impedance profiles were significantly constricted in reconstructions with dendritic atrophy, where these physiological measurements across dendritic locations converged to similar values. These results revealed that, in atrophied dendritic structures, the presence of an ion channel density gradient alone was insufficient to sustain homologous functional maps along the same neuronal topograph. We assessed the biophysical basis for these conclusions and found that this atrophy-induced constriction of functional maps was mediated by an enhanced spatial spread of the influence of an HCN-channel cluster in atrophied trees. These results demonstrated that the influence fields of ion channel conductances need to be localized for channel gradients to express themselves as homologous functional maps, suggesting that ion channel gradients are necessary but not sufficient for the emergence of functional maps within single neurons.

Aβ induces PUMA activation: a new mechanism for Aβ-mediated neuronal apoptosis

p53 upregulated modulator of apoptosis (PUMA) is a promising tumor therapy target because it elicits apoptosis and profound sensitivity to radiation and chemotherapy. However, inhibition of PUMA may be beneficial for curbing excessive apoptosis associated with neurodegenerative disorders. Alzheimer's disease (AD) is a representative neurodegenerative disease in which amyloid-β (Aβ) deposition causes neurotoxicity. The regulation of PUMA during Aβ-induced neuronal apoptosis remains poorly understood. Here, we reported that PUMA expression was significantly increased in the hippocampus of transgenic mice models of AD and hippocampal neurons in response to Aβ. PUMA knockdown protected the neurons against Aβ-induced apoptosis. Furthermore, besides p53, PUMA transactivation was also regulated by forkhead box O3a through p53-independent manner following Aβ treatment. Notably, PUMA contributed to neuronal apoptosis through competitive binding of apoptosis repressor with caspase recruitment domain to activate caspase-8 that cleaved Bid into tBid to accelerate Bax mitochondrial translocation, revealing a novel pathway of Bax activation by PUMA to mediate Aβ-induced neuronal apoptosis. Together, we demonstrated that PUMA activation involved in Aβ-induced apoptosis, representing a drug target to antagonize AD progression.

Effects of low frequency electric fields on synaptic integration in hippocampal CA1 pyramidal neurons: implications for power line emissions.

The possible cognitive effects of low frequency external electric fields (EFs), such as those generated by power lines, are poorly understood. Their functional consequences for mechanisms at the single neuron level are very difficult to study and identify experimentally, especially in vivo. The major open problem is that experimental investigations on humans have given inconsistent or contradictory results, making it difficult to estimate the possible effects of external low frequency electric fields on cognitive functions. Here we investigate this issue with realistic models of hippocampal CA1 pyramidal neurons. Our findings suggest how and why EFs, with environmentally observed frequencies and intensities far lower than what is required for direct neural activation, can perturb dendritic signal processing and somatic firing of neurons that are crucially involved in cognitive tasks such as learning and memory. These results show that individual neuronal morphology, ion channel dendritic distribution, and alignment with the electric field are major determinants of overall effects, and provide a physiologically plausible explanation of why experimental findings can appear to be small and difficult to reproduce, yet deserve serious consideration.

High-conductance states and A-type K+ channels are potential regulators of the conductance-current balance triggered by HCN channels.

An increase in the hyperpolarization-activated cyclic nucleotide-gated (HCN) channel conductance reduces input resistance, whereas the consequent increase in the inward h current depolarizes the membrane. This results in a delicate and unique conductance-current balance triggered by the expression of HCN channels. In this study, we employ experimentally constrained, morphologically realistic, conductance-based models of hippocampal neurons to explore certain aspects of this conductance-current balance. First, we found that the inclusion of an experimentally determined gradient in A-type K(+) conductance, but not in M-type K(+) conductance, tilts the HCN conductance-current balance heavily in favor of conductance, thereby exerting an overall restorative influence on neural excitability. Next, motivated by the well-established modulation of neuronal excitability by synaptically driven high-conductance states observed under in vivo conditions, we inserted thousands of excitatory and inhibitory synapses with different somatodendritic distributions. We measured the efficacy of HCN channels, independently and in conjunction with other channels, in altering resting membrane potential (RMP) and input resistance (Rin) when the neuron received randomized or rhythmic synaptic bombardments through variable numbers of synaptic inputs. We found that the impact of HCN channels on average RMP, Rin, firing frequency, and peak-to-peak voltage response was severely weakened under high-conductance states, with the impinging synaptic drive playing a dominant role in regulating these measurements. Our results suggest that the debate on the role of HCN channels in altering excitability should encompass physiological and pathophysiological neuronal states under in vivo conditions and the spatiotemporal interactions of HCN channels with other channels.

Effects of SKF83959 on the excitability of hippocampal CA1 pyramidal neurons: a modeling study.

3-Methyl-6-chloro-7,8-hydroxy-1-(3-methylphenyl)-2,3,4,5-tetrahydro-1H-3-benzazepine (SKF83959) have been shown to affect several types of voltage-dependent channels in hippocampal pyramidal neurons. The aim of this study was to determine how modulation of a individual type of the channels by SKF83959 contributes to the overall excitability of CA1 pyramidal neurons during either direct current injections or synaptic activation. Rat hippocampal slices were prepared. The kinetics of voltage-dependent Na(+) channels and neuronal excitability and depolarization block in CA1 pyramidal neurons were examined using whole-cell recording. A realistic mathematical model of hippocampal CA1 pyramidal neuron was used to simulate the effects of SKF83959 on neuronal excitability. SKF83959 (50 μmol/L) shifted the inactivation curve of Na(+) current by 10.3 mV but had no effect on the activation curve in CA1 pyramidal neurons. The effects of SKF83959 on passive membrane properties, including a decreased input resistance and depolarized resting potential, predicted by our simulations were in agreement with the experimental data. The simulations showed that decreased excitability of the soma by SKF83959 (examined with current injection at the soma) was only observed when the membrane potential was compensated to the control levels, whereas the decreased dendritic excitability (examined with current injection at the dendrite) was found even without membrane potential compensation, which led to a decreased number of action potentials initiated at the soma. Moreover, SKF83959 significantly facilitated depolarization block in CA1 pyramidal neurons. SKF83959 decreased EPSP temporal summation and, of physiologically greater relevance, the synaptic-driven firing frequency. SKF83959 decreased the excitability of CA1 pyramidal neurons even though the drug caused the membrane potential depolarization. The results may reveal a partial mechanism for the drug's anti-Parkinsonian effects and may also suggest that SKF83959 has a potential antiepileptic effect.

The suppression of epileptiform discharges in cultured hippocampal neurons is regulated via alterations in full-length tropomyosin-related kinase type B receptors signalling activity.

Epilepsy is a common neurological disease. Understanding the mechanisms of epileptogenesis at the cellular and molecular levels may provide novel targets for preventing this disorder. Brain-derived neurotrophic factor (BDNF) and its receptor tropomyosin-related kinase type B (TrkB) are believed to be critical for epileptogenesis. Previous studies have revealed possible changes in the expression of full-length TrkB receptors (TrkB.FL) and truncated TrkB receptors (TrkB.T) in neurodegenerative disorders. In this study, we investigated alterations in TrkB receptor expression and TrkB signalling activity in a rat hippocampal neuronal model of spontaneous recurrent epileptiform discharges (SREDs) and the effects on the epileptiform discharges. To induce epileptiform discharges, we established a model with Mg(2+) -free treatment. We found a dramatic upregulation of TrkB.T and a decrease in TrkB.FL in the SREDs model. Calpain contributed to the downregulation of TrkB.FL. The upregulation of TrkB.T required transcription and translation activity. Furthermore, BDNF induced the activation of TrkB.FL signalling. However, TrkB.FL signalling was inhibited in the SREDs model. Although calpain inhibitors prevented a decrease in TrkB.FL, they did not restrain the downregulation of TrkB.FL signalling activity in the model. However, a SREDs model with a translation inhibitor prevented the increase in TrkB.T and re-activated TrkB.FL signalling activity. Finally, we used electrophysiology to observe that a downregulation of TrkB.T could relieve the representative epileptiform discharges in the model. These results, taken together, demonstrate that alterations in TrkB.FL signalling may be regulated via TrkB.T receptors. Upregulation of TrkB.FL signalling suppresses epileptiform discharges in the SREDs model.

Establishment of SD neonatal rat hippocampal neuron models with human cytomegalovirus infection in vitro and preliminary study on calcium metabolism

Objective To investigate the influence of primary cultured neonatal rat hippocampal neurons caused by human cytomegalovirus (HCMV AD169)infection on intracellular calcium and its mechanism. Methods Twenty SPF SD rats born within 24 hours(10 cases of male and 10 cases of female) were assigned to establish the primary rat hippocampal neuronal monolayer cells; After cultured 8 days in vitro, the eligible cells were randomly divided into HCMV infection group, HCMV+ MK-801 group, MK-801 group and control group, with 10 wells in each group.The fluorescence intensity values of the intracellular free calcium were detected after 24 hours of treatment with Fluo-3AM fluorescence staining. Results Inoculation of HCMV neurons after 24 h turned to round and swollen gradually, and 4 days later, most of the cells disappeared; by immunohistochemistry in cultures of hippocampal neurons in HCMV, visible early proteins, brownish yellow granules, hematoxylin were found after being stained with brown pigment.The fluorescence intensity values of neuronal intracellular calcium (215.5±14.9) in HCMV group was higher than that of control group(116.4±5.9) (t=15.2, P<0.01), whilerise, that in MK-801 group (88.1±4.5) was significantly lower than that of control group, with decreased rate of (24.0±6.7)%(t=-9.3, P<0.01). The fluorescence intensity values of neuronal intracellular calcium in HCMV+ MK-801 group (135.5±8.6) was significantly decreased compared with that of HCMV group(215.5±14.9), with decreased rate of (37.0±3.4)%(t=11.3, P<0.01). Conclusions Intracellular calcium overload of cultured rat hippocampal neurons in vitro with HCMV AD16 strains infection can be detected.One of its main mechanisms is the N-methyl-D-aspartic acid receptor channel-mediated calcium influx. Key words: Laser scanning confocal microscope; Human cytomegalovirus; Rat neuron; Cell model; Calcium overload

Study on Bioinformatics with Dynamic Characteristics Change of the Hippocampal Neuron Model Caused by the Alzheimer Disease

In the paper, based on the electrophysiological experimental dada, the neuron model under the pathology condition of Alzheimer Disease (AD) is built. The neuron models dynamic variation characteristics before and after the effect of AD are comparatively studied. Under the currents stimulation, compared with the normal neuron model, the AD neuron models dynamic characteristics have been obviously changed. Its changing range of the membranes interspike intervals (ISIs) obviously narrows, and the discharge patterns change rather single. In addition, its discharge threshold is much higher than the normal neuron models. So AD causes the neuron models excitability to depress markedly. The research reveals the neuron models dynamic characteristics changing under the effect of AD, which shows bioinformatics change of the neuron caused by AD. The research provides some theoretic basis for AD research by the neurodynamics theory.

Blockade of SOCE protects HT22 cells from hydrogen peroxide-induced apoptosis

Oxidative stress is an established event in the pathology of neurobiological diseases. Previous studies indicated that store-operated Ca2+ entry (SOCE) has been involved in oxidative stress. The present study was carried out to investigate the effects of SOCE inhibition on neuronal oxidative stress injury induced by hydrogen peroxide (H2O2) in HT22 cells, a murine hippocampal neuronal model. H2O2 insult induced significant intracellular Ca2+ overload, mitochondrial dysfunction and cell viability decrease. Inhibition of SOCE by pharmacological inhibitor and STIM1 RNAi significantly alleviated intracellular Ca2+ overload, restored the mitochondrial membrane potential (MMP), decreased cytochrome C release and eventually inhibited H2O2-induced cell apoptosis. These findings suggest that SOCE inhibition exhibited neuroprotection against oxidative stress induced by H2O2 and SOCE might be a useful therapeutic target in neurobiological disorders.