Rat Organotypic Hippocampal Cultures Research Articles

A peptide derived from acetylcholinesterase induces neuronal cell death: characterisation of possible mechanisms.

Acetylcholinesterase (AChE) exhibits functions unrelated to the catalysis of acetylcholine (ACh) in particular during development. Although the underlying mechanism(s) is presently unknown, a candidate peptide fragment (AChE-peptide) has recently been identified, and been shown to induce a continuum of apoptotic and necrotic neuronal cell death in rat hippocampal organotypic cultures. The aim of this study was to trace the cell death pathway initiated by AChE-peptide. Using specific antagonists, it was possible to track a series of cellular events following application of 1 nM AChE-peptide: NMDA receptor activation, opening of the L-type voltage gated calcium channel, activation of calcium/calmodulin kinase II, generation of reactive oxygen species and caspase activation. Pharmacological interception at any stage of this cascade blocked the effect of 1 nM AChE-peptide on neurite retraction. Lactate dehydrogenase (LDH) release, a marker for cell lysis, was unaffected by 1 nM AChE-peptide. In contrast, cell death induced by 1 mM AChE-peptide, monitored as neurite retraction and increased LDH efflux, was not offset by any drug treatment. These data suggest that nanomolar concentrations of AChE-peptide exhibit pathophysiological activity via an apoptotic pathway that could play an important role in neuronal development and neurodegeneration.

Opposing effects of ethanol and nicotine on hippocampal calbindin-D 28k expression

Long-term ethanol exposure produces multiple neuroadaptations that likely contribute to dysregulation of Ca 2+ balance and neurotoxicity during ethanol withdrawal. Conversely, nicotine exposure may reduce the neurotoxic consequences of Ca 2+ dysregulation, putatively through up-regulation of the Ca 2+-buffering protein calbindin-D 28k. The current studies were designed to examine the extent to which 10-day ethanol exposure and withdrawal altered calbindin-D 28k expression in rat hippocampus. Further, in these studies, we examined the ability of nicotine, through action at α 7 ∗ -bearing nicotinic acetylcholine receptors (nAChRs), to antagonize the effects of ethanol exposure on calbindin-D 28k expression. Organotypic cultures of rat hippocampus were exposed to ethanol (50–100 mM) for 10 days. Additional cultures were exposed to 500 nM (–)-nicotine with or without the addition of 50 mM ethanol, 100 nM methyllycaconitine (an α 7 ∗ -bearing nAChR antagonist), or both. Prolonged exposure to ethanol (≥50 mM) produced significant reductions of calbindin-D 28k immunolabeling in all regions of the hippocampal formation, even at nontoxic concentrations of ethanol. Calbindin-D 28k expression levels returned to near-control levels after 72 h of withdrawal from 10-day ethanol exposure. Extended (–)-nicotine exposure produced significant elevations in calbindin-D 28k expression levels that were prevented by methyllycaconitine co-exposure. Co-exposure of cultures to (–)-nicotine with ethanol resulted in an attenuation of ethanol-induced reductions in calbindin-D 28k expression levels. These findings support the suggestion that long-term ethanol exposure reduces the neuronal capacity to buffer accumulated Ca 2+ in a reversible manner, an effect that likely contributes to withdrawal-induced neurotoxicity. Further, long-term exposure to (–)-nicotine enhances calbindin-D 28k expression in an α 7 ∗ nAChR–dependent manner and antagonizes the effects of ethanol on calbindin-D 28k expression.

γ-Aminobutyric Acid-A Receptors Contribute to Isoflurane Neuroprotection in Organotypic Hippocampal Cultures

The mechanisms by which anesthetics such as isoflurane reduce cell death in rodent models of cerebral ischemia remain incompletely defined. Reduction in glutamate excitotoxicity explains some but not all of isoflurane's neuroprotection. Because isoflurane potentiates gamma-aminobutyric acid (GABA) receptor-mediated ion fluxes and GABA(A) receptor agonists have neuroprotective effects, we hypothesized that GABA(A) receptors contribute to isoflurane neuroprotection. As a model of cerebral ischemia and recovery, we used rat hippocampal slice cultures. Survival of CA1, CA3, and dentate neurons was examined 2 and 3 days after 1-h combined oxygen-glucose deprivation (OGD) at 37 degrees C. To define the role of GABA(A) receptors in mediating protection, the effect of 1% isoflurane on cell survival was examined in the presence of the GABA(A) antagonist bicuculline during OGD. Cell death was measured with propidium iodide fluorescence. Isoflurane and the selective GABA(A) agonist muscimol (25 micro M) reduced cell death after OGD to values similar to slices not exposed to OGD, with the exception that muscimol did not reduce cell death in CA3 neurons 2 days after OGD. The GABA(A) antagonist bicuculline reduced the neuroprotective effects of isoflurane on hippocampal neurons 2 and 3 days after OGD. We conclude that GABA(A) receptors contribute to neuroprotection against OGD produced by isoflurane in the hippocampal slice model. Based on this and other studies, it is likely that neuroprotection produced by isoflurane is multifactorial and includes actions at both GABA(A) and glutamate receptors and possibly other mechanisms. Isoflurane is neuroprotective in rodent brain ischemia models, but the mechanisms for this effect remain incompletely defined. In organotypic cultures of rat hippocampus, we show that protection of CA1, CA3, and dentate neurons by 1% isoflurane from death caused by oxygen and glucose deprivation involves GABA(A) receptors.

Caffeic acid phenethyl ester (CAPE) prevents inflammatory stress in organotypic hippocampal slice cultures

Caffeic acid phenethyl ester (CAPE) is an antioxidant component of propolis, a natural product secreted by honeybee. Recent literature shows that CAPE inhibits nuclear factor κ B (NFκB) activation in cell lines. Since NFκB was shown to be a crucial factor in neuroinflammation and to be associated with some neuropathologies, CAPE might reduce these disorders in brain too and have therapeutic applications. To test this hypothesis we used a model of endotoxic insult (interferon-γ, followed by lipopolysaccharide) on rat organotypic hippocampal cultures. Cerebral inflammatory responses were strongly inhibited by CAPE (100 μM): reductions of NFκB nuclear activity, tumor necrosis factor α and nitric oxide productions were observed. At the dose of maximal effects (100 μM), an increase of cAMP-responsive element binding protein (CREB) activity, which anti-inflammatory role is well known, was seen. We compared CAPE effects with those of other drugs: anti-inflammatory as acetyl-salicylate and dexamethasone (glucocorticoid), antioxidant as pyrrolidine dithiocarbamate, or selective permeant inhibitor of NFκB as SN 50 peptide. These studies lead us to conclude that CAPE presents an interesting and original neuropharmacological profile compared to these drugs and might be helpful in the prevention of neurotoxic events due to excessive inflammatory reaction in brain. CAPE interferes with several effectors of neuroinflammation that might have complementary and synergic effects and allows a rather durable control since an acute treatment at the time of endotoxin exposure allows to control inflammatory factors for over 48 h.

Morphological evidence of the continuum between necrosis and apoptosis in model of anoxia in vitro

Growing evidence suggests that two modes of cell death, known as apoptosis and necrosis, are involved in postanoxic injury. The current opinion on these two types of cell death is that apoptosis and necrosis are not always the uniform and distinct events. The aim of this study was to determine ultrastructural criteria of postanoxic neuronal changes in model of anoxia in vitro. The organotypic cultures of rat hippocampus exposed to 10‐ and 20‐min of anoxic insult revealed the morphological features classic for both necrotic and apoptotic neuronal cell injury. Some neurones exhibited the typical necrotic lysis whereas others clearly reflected an active apoptotic form of cell death consisting of nuclear condensation with early preservation of cell membranes. However, numerous damaged cells shared both apoptotic and necrotic ultrastructural characteristics. These results evidenced the morphological continuum between apoptosis and necrosis under anoxia in vitro.

Neuroprotection of zinc against apoptotic cell death in model of anoxia in vitro

Zinc is the trace element considered the one of the etiological agents involved in nerve cell damage in certain human neurodegenerative disorders. Growing evidence indicates the diverse effect of zinc ions, associated with its neuroprotective and neurotoxic abilities. We examined the effect of zinc on the evolution of anoxia‐induced neuronal injury in the organotypic cultures of rat hippocampus. The cultures had been pretreated with ZnCl2 (25–500 μm) 30 min prior anoxia. The ultrastructural findings documented dose‐dependent ability of Zn to reduce anoxia‐induced neuronal changes in hippocampal neurones in vitro. The significant neuroprotection involved the development of late apoptotic changes, whereas the early necrotic anoxia‐induced neuronal injury was not significantly reduced. However, the quite‐well preserved pyramidal neurones displayed the mitochondrial abnormalities, reflecting the combined neuroprotective and neurotoxic Zn properties.

Searching for mechanisms of N-methyl-D-aspartate-induced glutathione efflux in organotypic hippocampal cultures.

N-Methyl-D-aspartate (NMDA)-receptor stimulation evoked a selective and partly delayed elevated efflux of glutathione, phosphoethanolamine, and taurine from organotypic rat hippocampus slice cultures. The protein kinase inhibitors H9 and staurosporine had no effect on the efflux. The phospholipase A2 inhibitors quinacrine and 4-bromophenacyl bromide, as well as arachidonic acid, a product of phospholipase A2 activity, did not affect the stimulated efflux. Polymyxin B, an antimicrobal agent that inhibits protein kinase C, and quinacrine in high concentration (500 microM), blocked efflux completely. The stimulated efflux after but not during NMDA incubation was attenuated by a calmodulin antagonist (W7) and an anion transport inhibitor (DNDS). Omission of calcium increased the spontaneous efflux with no or small additional effects by NMDA. In conclusion, NMDA receptor stimulation cause an increased selective efflux of glutathione, phosphoethanolamine and taurine in organotypic cultures of rat hippocampus. The efflux may partly be regulated by calmodulin and DNDS sensitive channels.

Postsynaptic Expression of a New Calcium Pathway in Hippocampal CA3 Neurons and Its Influence on Mossy Fiber Long-Term Potentiation

Long-term potentiation (LTP) in the CA1 region of the hippocampus is induced by postsynaptic Ca(2+) influx via NMDA receptors (NMDARs). However, this synaptic plasticity occurs independently of NMDARs when Ca(2+)-permeable AMPA receptors (AMPARs) are expressed at postsynaptic sites using various genetic techniques, indicating that an increase in Ca(2+) level at critical postsynaptic sites, regardless of its entry pathway, triggers the induction of LTP at CA1 synapses. In contrast, NMDARs are sparsely distributed on mossy fiber (MF) synapses in CA3 hippocampal neurons, and most evidence favors the presynaptic mechanism for LTP induction, although some reports suggested a postsynaptic mechanism. In this study, we examined whether Ca(2+) influx through the newly produced postsynaptic receptors during high-frequency stimulation affects the induction of MF LTP. For this purpose, we expressed Ca(2+)-permeable AMPARs in CA3 pyramidal neurons by Sindbis viral-mediated gene transfer of the unedited form of the glutamate receptor 2 (GluR2Q) subunit, as a new pathway for postsynaptic Ca(2+) entry, in rat hippocampal organotypic cultures. Virally expressed myc-tagged GluR2Q was detected at the complex spines known as the thorny excrescences, which serve as postsynaptic targets for MF synaptic input, on the proximal apical dendrites of CA3 pyramidal cells. Furthermore, endogenous Ca(2+)-impermeable AMPARs at MF synapses were converted into Ca(2+)-permeable receptors by GluR2Q expression. However, the postsynaptic expression of Ca(2+)-permeable AMPARs had no significant influence on the two types of MF LTP induced by different stimulus protocols. These results supported the notion that MF LTP is independent of postsynaptic Ca(2+).

Bismuth tracing in organotypic cultures of rat hippocampus

Bismuth is known to have neurotoxic side effects in humans and animals. In the 1970s France experienced about a thousand cases of patients suffering from bismuth-induced encephalopathy. Studies suggest that bismuth may provoke a selective degeneration of CA1 pyramidal cells in the organotypic cultures of rat hippocampus. A currently established technique for the histochemical visualization of bismuth was applied on hippocampal tissue cultures allowing the tracing of bismuth in concentrations hitherto not possible. The accumulation and subcellular localization of bismuth is demonstrated in the tissue cultures of rat hippocampus. CA1 pyramidal cells in the rat hippocampus exhibit the highest uptake of bismuth. High bismuth citrate concentrations (10 μM) are able to totally destroy the cytoarchitecture of the hippocampus. At ultrastructural levels bismuth was found to be located exclusively in lysosome-like organelles.

Evaluation of drugs acting at glutamate transporters in organotypic hippocampal cultures: new evidence on substrates and blockers in excitotoxicity.

Removal of L-glutamate (Glu) from the synapse is critical to maintain normal transmission and to prevent excitotoxicity, and is performed exclusively by excitatory amino acid transporters (EAATs). We investigated the effects of substrates and blockers of EAATs on extracellular Glu and cellular viability in organotypic cultures of rat hippocampus. Seven-day treatment with a range of drugs (L-trans-pyrrolidine-2,4-dicarboxylate, (2S,4R)-4-methyl-glutamate, (+/-)-threo-3-methylglutamate and DL-threo-beta-benzyloxyaspartate), in the presence of 300 microM added Glu, resulted in increased extracellular Glu and a significant correlation between Glu concentration and cellular injury (as indicated by lactate dehydrogenase release). In contrast, (2S,3s,4R)-2-(carboxycyclopropyl)glycine (L-CCG-III) exerted a novel neuroprotection against this toxicity, and elevations in extracellular Glu were not toxic in the presence of this compound. Similar results were obtained following two-week treatment of cultures without added Glu. Whilst blockade of GLT-1 alone was relatively ineffective in producing excitotoxic injury, heteroexchange of Glu by EAAT substrates may exacerbate excitotoxicity.

The Protective Effect of ZnCl 2 Pretreatment on the Development of Postanoxic Neuronal Damage in Organotypic Rat Hippocampal Cultures

Zinc is one of the trace elements playing an important role in many fundamental biological processes. However, it is also one of the possible etiological agents involved in nerve cell damage in certain human neurodegenerative disorders. The precise mechanism of neuroprotective ability of Zn against neurotoxicity evidenced in various pathological conditions remains unclear, especially concerning the intrinsic potential toxicity of this metal. This ultrastructural study was undertaken to determine the effect of zinc on the evolution of anoxia-induced neuronal injury in the organotypic cultures of rat hippocampus. The in vitro model of oxygen deprivation was produced by maintaining the cultures in a pure nitrogen atmosphere in flask adapted for permanent gas flow for 20 min. The selected cultures were pretreated with micromolar concentration of ZnCl 2 (25-500 µM) at 30 min prior anoxia. The ultrastructural findings documented that Zn exhibited dose-dependent ability to reduce anoxia-induced neuronal changes in hippocampal neurons in vitro. Zn at a concentration of 100 µM was able to significantly protect the hippocampal formation against the development of late apoptotic changes, whereas the early necrotic anoxia-induced neuronal injury was not so efficiently reduced.

Chronic nicotine exposure reduces N-methyl- d-aspartate receptor-mediated damage in the hippocampus without altering calcium accumulation or extrusion: evidence of calbindin-D28K overexpression

Neuronal accumulation of excess Ca 2+ has been implicated in cellular death following several forms of physical and chemotoxic insult. Recent studies have suggested that exposure to agonists at brain nicotinic acetylcholine receptors reduces cytotoxic consequences of increased intracellular Ca 2+ following some insults. In the present study, the ability of chronic exposure to (−)-nicotine to reduce cytotoxicity and attenuate increases in intracellular Ca 2+ caused by exposure to N-methyl- d-aspartate were examined in organotypic cultures of rat hippocampus. Cultures were exposed to nicotine (0.1–10.0 μM) for five days prior to excitotoxic insult with N-methyl- d-aspartate. Exposure to N-methyl- d-aspartate produced concentration-dependent increases in both accumulation of 45Ca and in early and delayed cell death in the CA1, CA3 and dentate gyrus regions of cultures. The CA1 region of the hippocampus displayed the greatest sensitivity to cytotoxic effects of N-methyl- d-aspartate exposure; however, this regional difference was not associated with increased accumulation of 45Ca. Prior exposure to nicotine markedly attenuated N-methyl- d-aspartate-induced early and delayed cell death in each hippocampal region at concentrations as low as 0.1 μM. However, nicotine did not alter the initial N-methyl- d-aspartate-stimulated influx of 45Ca or enhance extrusion of accumulated 45Ca measured at several time-points after insult. Five days of exposure to nicotine markedly increased immunoreactivity of the Ca 2+ binding protein calbindin-D28K in each region of hippocampal cultures, effects reduced by mecamylamine co-exposure. These findings suggest that the potent protective effects of chronic nicotine exposure against neuronal overexcitation are not likely attributable to attenuations of Ca 2+ accumulation, but are likely related to increased buffering of accumulated Ca 2+.

Regulation of β-amyloid induced cytokine and chemokine expression in rat organotypic hippocampal cultures by macrophage colony stimulating factor

Regulation of β-amyloid induced cytokine and chemokine expression in rat organotypic hippocampal cultures by macrophage colony stimulating factor

Fluorescence microscopy of stimulated Zn(II) release from organotypic cultures of mammalian hippocampus using a carbonic anhydrase-based biosensor system

We demonstrate here that electrical stimulation of organotypic cultures of rat hippocampus results in the prompt release of significant amounts of Zn(II) by a fluorescence microscopic method. The fluorescence imaging of free Zn(II) is achieved using a highly selective biosensing indicator system consisting of human apo-carbonic anhydrase II (apoCAII) and a fluorescent aryl sulfonamide inhibitor of the enzyme, ABD-N. The apoenzyme and ABD-N in the absence of Zn(II) exhibit weak, reddish fluorescence typical of the ABD-N alone; when Zn(II) is added it binds to the apoenzyme ( K D=4 pM), which strongly promotes binding of ABD-N to the holoenzyme ( K D=0.9 μM). Binding of ABD-N to the holoenzyme results in a 9-fold increase in apparent quantum yield, significant blue shifts in excitation and emission, an increase in average fluorescence lifetime, a 4-fold increase in the ratio of intensities at 560 and 680 nm, and a large increase in anisotropy. Prior to stimulation, cultures immersed in phosphate-buffered saline with glucose and apoCAII with ABD-N emitted negligible fluorescence, but within 20 s after electrical stimulation a diffuse cloud of greenish fluorescence emerged and subsequently covered most of the culture, indicating release of zinc into the extracellular medium.

Adverse effects of an active fragment of parathyroid hormone on rat hippocampal organotypic cultures.

Adverse effects of an active fragment of parathyroid hormone (PTH(1 - 34)), a blood Ca(2+) level-regulating hormone, were examined using rat hippocampal slices in organotypic culture. Exposure of cultured slice preparations to 0.1 microM PTH(1 - 34) for 60 min resulted in a gradual increase in the intracellular Ca(2+) concentration ([Ca(2+)](i)); this effect was most obvious in the apical dendritic region of CA1 subfield. When PTH(1 - 34) at a lower concentration (1 nM) was added to the culture medium and its toxic effects examined using a propidium iodide intercalation method, significant toxicity was seen 3 days after exposure and increased with time. Cells in the CA1 region seemed more vulnerable to the hormone than cells in other regions. At 1 week of exposure, the toxic effects were dose-dependent over the range of 0.1 pM to 0.1 microM, the minimum effective dose being 10 pM. The adverse effects were not induced either by the inactive fragment, PTH(39 - 84), or by an active fragment of PTH-related peptide (PTHrP(1 - 34)), an intrinsic ligand of the brain PTH receptor. The PTH(1 - 34)-induced adverse effects were significantly inhibited by co-administration of 10 microM nifedipine, an L-type Ca(2+) channel blocker, but not by co-administration of blockers of the other types of Ca(2+) channel. The present study demonstrates that sustained high levels of PTH in the brain might cause degeneration of specific brain regions due to Ca(2+) overloading via activation of dihydropyridine-sensitive Ca(2+) channels, and suggests that PTH may be a risk factor for senile dementia. British Journal of Pharmacology (2000) 129, 21 - 28

1-Aminoindan-1,5-dicarboxylic acid and (S)-(+)-2-(3'-carboxybicyclo[1.1.1] pentyl)-glycine, two mGlu1 receptor-preferring antagonists, reduce neuronal death in in vitro and in vivo models of cerebral ischaemia.

Metabotropic glutamate (mGlu) receptors have been implicated in a number of physiological and pathological responses to glutamate, but the exact role of group I mGlu receptors in causing postischaemic injury is not yet clear. In this study, we examined whether the recently-characterized and relatively selective mGlu1 receptor antagonists 1-aminoindan-1,5-dicarboxylic acid (AIDA) and (S)-(+)-2-(3'-carboxybicyclo[1.1.1]pentyl)-glycine (CBPG) could reduce neuronal death in vitro, following oxygen-glucose deprivation (OGD) in murine cortical cell and rat organotypic hippocampal cultures, and in vivo, after global ischaemia in gerbils. When present in the incubation medium during the OGD insult and the subsequent 24 h recovery period, AIDA and CBPG significantly reduced neuronal death in vitro. The extent of protection was similar to that observed with the nonselective mGlu receptor antagonist (+)-alpha-methyl-4-carboxyphenylglycine [(+)MCPG] and with typical ionotropic glutamate (iGlu) receptor antagonists. Neuroprotection was also observed when AIDA or CBPG were added only after the OGD insult was terminated. Neuronal injury was not attenuated by the inactive isomer (-)MCPG, but was significantly enhanced by the nonselective mGlu receptor agonist (1S,3R)-1-aminocyclopentane-1, 3-dicarboxylic acid [(1S,3R)-ACPD] and the group I mGlu receptor agonist 3,5-dihydroxyphenylglycine (3,5-DHPG). The antagonists (+)MCPG, AIDA and CBPG were also neuroprotective in vivo, because i. c.v. administration reduced CA1 pyramidal cell degeneration examined 7 days following transient carotid occlusion in gerbils. Our results point to a role of mGlu1 receptors in the pathological mechanisms responsible for postischaemic neuronal death and propose a new target for neuroprotection.

Synaptic transmission at nicotinic acetylcholine receptors in rat hippocampal organotypic cultures and slices.

1. Whole-cell clamp recordings of the compound synaptic current elicited by afferent stimulation of Schaffer collaterals showed that blockade of the NMDA, AMPA and GABAA receptor-mediated components by 6-nitro-7-sulphamoyl- benzo(f)quinoxaline-2,3-dione (NBQX), 3-((R)-2-carboxypiperazine-4-yl)propyl-1-phosphonate (R-CPP) and picrotoxin, respectively, left a small residual current in 39 out of 41 CA1 pyramidal neurones in organotypic cultures and 9 out of 16 CA1 cells in acutely prepared slices. 2. This current represented 2. 9 +/- 0.4 % of the compound evoked synaptic response in organoypic cultures and 1.4 +/- 0.5 % in slices. It was characterized by a slightly rectifying I-V curve and a reversal potential of 3.4 +/- 5. 1 mV. 3. This residual current was insensitive to blockers of GABAB, purinergic, muscarinic and 5-HT3 receptors, but it was essentially blocked by the nicotinic receptor antagonist d-tubocurarine (91 +/- 4 % blockade; 20 microM), and partly blocked by alpha-bungarotoxin (200 nM) and methyllycaconitine (10 nM), two antagonists with a higher selectivity for alpha7 subunit-containing nicotinic receptors (48 +/- 3 % and 55 +/- 11 % blockade, respectively). 4. The residual current was of synaptic origin, since it occurred after a small delay; its amplitude depended upon the stimulation intensity and it was calcium dependent and blocked by the sodium channel antagonist tetrodotoxin. 5. We conclude that afferent stimulation applied in the stratum radiatum evokes in some hippocampal neurones a small synaptic current mediated by activation of neuronal nicotinic receptors.

P–415 - Adverse effects of an active fragment of parathyroid hormone on rat hippocampal organotypic cultures

P–415 - Adverse effects of an active fragment of parathyroid hormone on rat hippocampal organotypic cultures

Effects of the 3-hydroxyanthranilic acid analogue NCR-631 on anoxia-, IL-1 beta- and LPS-induced hippocampal pyramidal cell loss in vitro.

The kynurenine pathway intermediate 3-hydroxyanthranilic acid (3-HANA) is converted by 3-HANA 3,4-dioxygenase (3-HAO) to the putative neuropathogen quinolinic acid (QUIN). In the present study, the neuroprotective effects of the 3-HANA analogue and 3-HAO inhibitor NCR-631 was investigated using organotypic cultures of rat hippocampus. An anoxic lesion was induced by exposing the cultures to 100% N2 for 150 min, resulting in a pronounced loss of pyramidal neurons, as identified using NMDA-R1 receptor subunit immunohistochemistry. NCR-631 provided a concentration-dependent protective effect against the anoxia. NCR-631 was also found to counteract the loss of pyramidal neurons in two models of neuroinflammatory-related damage; incubation with either LPS (10 ng/ml) or IL-1 beta (10 IU/ml). The findings suggest that NCR-631 has neuroprotective properties and that it may be a useful tool to study the role of kynurenines in neurodegeneration.

Electrophysiological approach of the antiepileptic effect of dexamethasome on hippocampal slice culture usihg a multirecording system: The physiocard®

The in vitro antiepileptic activity of the synthetic glucocorticoid dexamethasone (DEX) was tested in rat hippocampal organotypic cultures on the field potential epileptiform activity induced by picrotoxin (PTX). Spontaneous as well as evoked electrophysiological activities have been studied through the extracellular multirecording Physiocard® system. PTX typically elicited seizure-like discharges (epileptiform bursts) in the hippocampus neurons. Those epileptiform bursts can be divided in two groups, one rhythmic which lasted 43 ± 24s (mean ± sd) at a frequency of 4.6 ± 1.9Hz and the other arhythmic composed of population spikes, which occurred during 14.3 ± 6.9min. In the presence of DEX at different concentrations, results obtained were: 1) DEX 1μM decreased the occurrence of the two different groups of spontaneous epileptiform bursts, most of the time to zero. 2) DEX 50μM prevented totally the occurrence of epileptiform bursts. 3) DEX 50μM contrarily to DEX 1μM avoided the decrease of evoked field potentials' amplitude induced by PTX 3μM on all simultaneous recorded points. Those results suggest that synthetic glucocorticoid DEX presents an acute antiepileptic effect in a dose dependent manner on the hippocampus tissue.