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Rat Hippocampal Slices (rat + hippocampal_slice)
Selected AbstractsCooling Abolishes Neuronal Network Synchronization in Rat Hippocampal SlicesEPILEPSIA, Issue 6 2002Sam P. Javedan Summary: ,Purpose: We sought to determine whether cooling brain tissue from 34 to 21°C could abolish tetany-induced neuronal network synchronization (gamma oscillations) without blocking normal synaptic transmission. Methods: Intracellular and extracellular electrodes recorded activity in transverse hippocampal slices (450,500 ,m) from Sprague,Dawley male rats, maintained in an air,fluid interface chamber. Gamma oscillations were evoked by afferent stimulation at 100 Hz for 200 ms. Baseline temperature in the recording chamber was 34°C, reduced to 21°C within 20 min. Results: Suprathreshold tetanic stimuli evoked membrane potential oscillations in the 40-Hz frequency range (n = 21). Gamma oscillations induced by tetanic stimulation were blocked by bicuculline, a ,-aminobutyric acid (GABA)A -receptor antagonist. Cooling from 34 to 21°C reversibly abolished gamma oscillations in all slices tested. Short, low-frequency discharges persisted after cooling in six of 14 slices. Single-pulse,evoked potentials, however, were preserved after cooling in all cases. Latency between stimulus and onset of gamma oscillation was increased with cooling. Frequency of oscillation was correlated with chamber cooling temperature (r = 0.77). Tetanic stimulation at high intensity elicited not only gamma oscillation, but also epileptiform bursts. Cooling dramatically attenuated gamma oscillation and abolished epileptiform bursts in a reversible manner. Conclusions: Tetany-induced neuronal network synchronization by GABAA -sensitive gamma oscillations is abolished reversibly by cooling to temperatures that do not block excitatory synaptic transmission. Cooling also suppresses transition from gamma oscillation to ictal bursting at higher stimulus intensities. These findings suggest that cooling may disrupt network synchrony necessary for epileptiform activity. [source] Contribution of T-type VDCC to TEA-induced long-term synaptic modification in hippocampal CA1 and dentate gyrusHIPPOCAMPUS, Issue 5 2002Dong Song Abstract We have previously reported that exposure to the K+ channel blocker tetraethylammonium (TEA), 25 mM, induces long-term potentiation (LTP) in CA1, but not in the dentate gyrus (DG), of the rat hippocampal slice. During TEA application, stimulation of excitatory afferents results in a strong depolarizing potential after the fast excitatory postsynaptic potential (EPSP) in CA1, but not in DG. We hypothesized that the differential effect of TEA on long-term synaptic modification in CA1 and DG results from different levels of TEA-elicited depolarization in the two cell types. Additional pharmacological studies showed that blockade of T-type voltage-dependent calcium channels (VDCCs) decreased both the magnitude of LTP and the late, depolarizing potential in CA1. Blockade of L-type VDCCs had no such effect. Using computer models of morphologically reconstructed CA1 pyramidal cells and DG granule cells, we tested our hypothesis by simulating the relative intracellular Ca2+ accumulation and membrane potential changes mediated by T-type and L-type VDCCs. Simulation results using pyramidal cell models showed that, with decreased maximum conductance of TEA-sensitive potassium channels, synaptic inputs elicited strong depolarizing potentials similar to those observed with intracellular recording. During this depolarization, VDCCs were opened and resulted in a large intracellular Ca2+ accumulation that presumably caused LTP. When T-type VDCCs were blocked, the magnitudes of both the Ca2+ accumulation and the late depolarizing potential were decreased substantially. Simulated blockade of L-type VDCCs had only a minor effect. Together, our modeling and experimental studies indicate that T-type VDCCs, rather than L-type VDCCs, are primarily responsible for facilitating the depolarizing potential caused by TEA and for the consequent Ca2+ influx. Thus, our findings strongly suggest that the induction of TEA-LTP in CA1 depends primarily on T-type, rather than L-type, VDCCs. Simulation results using modeled granule cells suggests that the failure of TEA to induce LTP in DG is partly due to a low density of T-type VDCCs in granule cell membranes. Hippocampus 2002;12:689,697. © 2002 Wiley-Liss, Inc. [source] A Possible Role for Gap Junctions in Generation of Very Fast EEG Oscillations Preceding the Onset of, and Perhaps Initiating, SeizuresEPILEPSIA, Issue 2 2001Roger D. Traub Summary: ,Purpose: We propose an experimentally and clinically testable hypothesis, concerning the origin of very fast (>,70 Hz) EEG oscillations that sometimes precede the onset of focal seizures. These oscillations are important, as they may play a causal role in the initiation of seizures. Methods: Subdural EEG recordings were obtained from children with focal cortical dysplasias and intractable seizures. Intra- and extracellular recordings were performed in rat hippocampal slices, with induction of population activity, as follows: (a) bath-applied tetramethylamine (an intracellular alkalinizing agent, that opens gap junctions); (b) bath-applied carbachol, a cholinergic agonist; and (c) focal pressure ejection of hypertonic K+ solution. Detailed network simulations were performed, the better to understand the cellular mechanisms underlying oscillations. A major feature of the simulations was inclusion of axon,axon gap junctions between principal neurons, as supported by recent experimental data. Results: Very fast oscillations were found in children before seizure onset, but also superimposed on bursts during the seizure, and on interictal bursts. In slice experiments, very fast oscillations had previously been seen on interictal-like bursts; we now show such oscillations before, between, and after epileptiform bursts. Very fast oscillations were also seen superimposed on gamma (30,70 Hz) oscillations induced by carbachol or hypertonic K+, and in the latter case, very fast oscillations became continuous when chemical synapses were blocked. Simulations replicate these data, when axonal gap junctions are included. Conclusions: Electrical coupling between principal neurons, perhaps via axonal gap junctions, could underlie very fast population oscillations, in seizure-prone brain, but possibly also in normal brain. The anticonvulsant potential of gap-junction blockers such as carbenoxolone, now in clinical use for treatment of ulcer disease, should be considered. [source] N -methyl- d -aspartate receptor- and metabotropic glutamate receptor-dependent long-term depression are differentially regulated by the ubiquitin-proteasome systemEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 8 2009Ami Citri Abstract Long-term depression (LTD) in CA1 pyramidal neurons can be induced by activation of either N -methyl- d -aspartate receptors (NMDARs) or metabotropic glutamate receptors (mGluRs), both of which elicit changes in synaptic efficacy through ,-amino-3-hydroxyl-5-methyl-4-isoxazole-propionate receptor (AMPAR) endocytosis. To address the role of the ubiquitin-proteasome system in regulating AMPAR endocytosis during these forms of LTD, we examined the effects of pharmacological inhibitors of proteasomal degradation and protein ubiquitination on endocytosis of glutamate receptor 1 (GluR1) -containing AMPARs in dissociated rat hippocampal cultures as well as LTD of excitatory synaptic responses in acute rat hippocampal slices. Our findings suggest that the contribution of the ubiquitin-proteasome system to NMDAR-induced vs. mGluR-induced AMPAR endocytosis and the consequent LTD differs significantly. NMDAR-induced AMPAR endocytosis and LTD occur independently of proteasome function but appear to depend, at least in part, on ubiquitination. In contrast, mGluR-induced AMPAR endocytosis and LTD are enhanced by inhibition of proteasomal degradation, as well as by the inhibitor of protein ubiquitination. Furthermore, the decay of mGluR-induced membrane depolarization and Erk activation is delayed following inhibition of either ubiquitination or proteasomal degradation. These results suggest that, although NMDAR-dependent LTD may utilize ubiquitin as a signal for AMPAR endocytosis, mGluR-induced signaling and LTD are limited by a feedback mechanism that involves the ubiquitin-proteasome system. [source] Spontaneous recurrent network activity in organotypic rat hippocampal slicesEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 1 2005Majid H. Mohajerani Abstract Organotypic hippocampal slices were prepared from postnatal day 4 rats and maintained in culture for >6 weeks. Cultured slices exhibited from 12 days in vitro spontaneous events which closely resembled giant depolarizing potentials (GDPs) recorded in neonatal hippocampal slices. GDP-like events occurred over the entire hippocampus with a delay of 30,60 ms between two adjacent regions as demonstrated by pair recordings from CA3,CA3, CA3,CA1 and interneurone,CA3 pyramidal cells. As in acute slices, spontaneous recurrent events were generated by the interplay of GABA and glutamate acting on AMPA receptors as they were reversibly blocked by bicuculline and 6,7-dinitroquinoxaline-2,3-dione but not by dl -2-amino-5-phosphonopentaoic acid. The equilibrium potentials for GABA measured in whole cell and gramicidin-perforated patch from interconnected interneurones,CA3 pyramidal cells were ,70 and ,56 mV, respectively. The resting membrane potential estimated from the reversal of N -methyl- d -aspartate-induced single-channel currents in cell-attach experiments was ,75 mV. In spite of its depolarizing action, in the majority of cases GABA was still inhibitory as it blocked the firing of principal cells. The increased level of glutamatergic connectivity certainly contributed to network synchronization and to the development of interictal discharges after prolonged exposure to bicuculline. In spite of its inhibitory action, in a minority of cells GABA was still depolarizing and excitatory as it was able to bring principal cells to fire, suggesting that a certain degree of immaturity is still present in cultured slices. This was in line with the transient bicuculline-induced block of GDPs and with the isoguvacine-induced increase of GDP frequency. [source] Presynaptic inhibition of Schaffer collateral synapses by stimulation of hippocampal cholinergic afferent fibresEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 3 2003David Fernández de Sevilla Abstract It has been known for decades that muscarinic agonists presynaptically inhibit Schaffer collateral synapses contacting hippocampal CA1 pyramidal neurons. However, a demonstration of the inhibition of Schaffer collateral synapses induced by acetylcholine released by cholinergic hippocampal afferents is lacking. We present original results showing that electrical stimulation at the stratum oriens/alveus with brief stimulus trains inhibited excitatory postsynaptic currents evoked by stimulation of Schaffer collaterals in CA1 pyramidal neurons of rat hippocampal slices. The increased paired-pulse facilitation and the changes in the variance of excitatory postsynaptic current amplitude that paralleled the inhibition suggest that it was mediated presynaptically. The effects of oriens/alveus stimulation were inhibited by atropine, and blocking nicotinic receptors with methyllycaconitine was ineffective, suggesting that the inhibition was mediated via the activation of presynaptic muscarinic receptors. The results provide a novel demonstration of the presynaptic inhibition of glutamatergic neurotransmission by cholinergic fibres in the hippocampus, implying that afferent cholinergic fibres regulate the strength of excitatory synaptic transmission. [source] 5,7-dihydroxytryptamine lesions enhance and serotonergic grafts normalize the evoked overflow of acetylcholine in rat hippocampal slicesEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 10 2002Anja Birthelmer Abstract Adult rats were subjected to intracerebroventricular injections of 5,7-dihydroxytryptamine (5,7-DHT; 150 µg) and, 15 days later, to intrahippocampal grafts of fetal raphe cell suspensions. About 11 months later, we assessed baseline and electrically evoked release of tritium ([3H]) in hippocampal slices, preloaded with tritiated ([3H])choline or [3H]serotonin (5-HT), in the presence or absence of the 5-HT1B receptor agonist CP-93,129 and the 5-HT receptor antagonist methiothepine. HPLC determinations of monoamine concentrations were also performed. The lesions reduced the concentration of 5-HT (,90%) and the accumulation (,80%) as well as the evoked release (,90%) of [3H]5-HT. They also decreased the inhibitory effects of CP-93,129 on the evoked release of [3H]5-HT. Most interestingly, they facilitated the evoked release of [3H]acetylcholine (+20%). In slices from rats subjected to lesions and grafts, the responsiveness of the serotonergic autoreceptors (presumably located on the terminals of the grafted neurons) and the release of acetylcholine were close to normal. These results confirm that grafts rich in serotonergic neurons may partially compensate for the dramatic effects of 5,7-DHT lesions on serotonergic hippocampal functions. The lesion-induced reduction of the 5-HT1B autoreceptor-mediated inhibition of evoked 5-HT release may be an adaptation enhancing serotonergic transmission in the (few) remaining terminals. The facilitated release of acetylcholine is probably caused by a reduced serotonergic tone on the inhibitory 5-HT1B heteroreceptors of the cholinergic terminals. When related to data in the literature, this facilitation may be of particular interest in terms of transmitter-based strategies developed to tackle cognitive symptoms related to neurodegenerative diseases. [source] Activity- and age-dependent GABAergic synaptic plasticity in the developing rat hippocampusEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 12 2001Paolo Gubellini Abstract Activity-dependent plasticity of GABAergic synaptic transmission was investigated in rat hippocampal slices obtained between postnatal day (P) 0,15 using the whole-cell patch-clamp recording technique. Spontaneous GABAA receptor-mediated postsynaptic currents (sGABAA -PSCs) were isolated in the presence of ionotropic glutamate receptor antagonists. A conditioning protocol relevant to the physiological condition, consisting of repetitive depolarizing pulses (DPs) at 0.1 Hz, was able to induce long-lasting changes in both frequency and amplitude of sGABAA -PSCs between P0 and P8. Starting from P12, DPs were unable to induce any form of synaptic plasticity. The effects of DPs were tightly keyed to the frequency at which they were delivered. When delivered at a lower (0.05 Hz) or higher (1 Hz) frequency, DPs failed to induce any long-lasting change in the frequency or amplitude of sGABAA -PSCs. In two cases, DPs were able to activate sGABAA -PSCs in previously synaptically silent cells at P0,1. These results show that long-term changes in GABAergic synaptic activity can be induced during a restricted period of development by a conditioning protocol relevant to the physiological condition. It is suggested that such activity-induced modifications may represent a physiological mechanism for the functional maturation of GABAergic synaptic transmission. [source] Exogenous nitric oxide causes potentiation of hippocampal synaptic transmission during low-frequency stimulation via the endogenous nitric oxide,cGMP pathwayEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 4 2001Christelle L. M. Bon Abstract Nitric oxide (NO) is a putative participant in synaptic plasticity and demonstrations that exogenous NO can elicit the same plastic changes have been taken to support such a role. The experiments, carried out on the CA1 region of rat hippocampal slices, were aimed at testing this interpretation. A major component of tetanus-induced long-term potentiation (LTP) was lost in response to l -nitroarginine, which inhibits NO synthase, and 1H -[1,2,4]oxadiazolo[4,3- a]quinoxalin-1-one (ODQ), which inhibits NO-sensitive soluble guanylyl cyclase (sGC). At 0.2 Hz afferent fibre stimulation, exogenous NO produced, concentration-dependently, a synaptic depression that reverted on washout to a persistent potentiation that occluded tetanus-induced LTP. The NO concentrations necessary (estimated in the 100-nm range), however, were mostly supramaximal for stimulating hippocampal slice sGC activity. Nevertheless the potentiation, but not the preceding depression, was blocked by ODQ. l -nitroarginine and an NMDA antagonist were similarly effective, indicating mediation by the endogenous NMDA receptor,NO synthase,sGC pathway. At a concentration normally too low to affect synaptic transmission but sufficient to stimulate sGC (estimated to be 50 nm), exogenous NO reversed the effect of l -nitroarginine and caused a potentiation which was blocked by ODQ. At a concentration inducing the depression/potentiation sequence, NO partially inhibited hippocampal slice oxygen consumption. It is concluded that, at physiological levels, exogenous NO can directly elicit a potentiation of synaptic transmission through sGC, provided that the synapses are suitably primed. At higher concentrations, NO inhibits mitochondrial respiration, which can result in an enduring synaptic potentiation due to secondary activation of the endogenous NO,cGMP pathway. [source] Differential induction of LTP and LTD is not determined solely by instantaneous calcium concentration: an essential involvement of a temporal factorEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 4 2001Tomoyuki Mizuno Abstract Two opposite types of synaptic plasticity in the CA1 hippocampus, long-term potentiation (LTP) and long-term depression (LTD), require postsynaptic Ca2+ elevation. To explain these apparently contradictory phenomena, the current view assumes that a moderate postsynaptic increase in Ca2+ leads to LTD, whereas a large increase leads to LTP. No detailed study has so far been attempted to investigate whether the instantaneous Ca2+ elevation level differentially induces LTP or LTD. We therefore used low-frequency (1 Hz) stimulation of Schaffer collateral/commissural fibers in rat hippocampal slices, during a Mg2+ -free period, as the conditioning stimulus to investigate this. This allowed low-frequency afferent stimulation to cause a postsynaptic Ca2+ influx because the voltage-dependent block of N -methyl- d -aspartate (NMDA) receptor-channels by Mg2+ was removed. When delivered during the Mg2+ -free period, a single pulse, as well as 2,600 pulses, induced LTP that was occluded with tetanus-induced LTP. To decrease the Ca2+ influx, ,-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) receptors were completely blocked by the addition of 10 µm 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) to the conditioning medium, in which 1 Hz afferent stimuli (1,600 pulses) induced less LTP and never induced LTD. To further reduce the Ca2+ influx, NMDA receptors were partially blocked with d -(,)-2-amino-5-phosphonopentanoic acid (d -AP5). A small number of 1 Hz stimuli, however, never induced LTD. Only when the conditioning stimuli exceeded 200 pulses was LTD induced. The present findings provide definitive evidence that protracted conditioning is a prerequisite for the induction of LTD. Thus, not only the amplitude but also the duration of postsynaptic Ca2+ elevation could be essential factors for differentially inducing LTP or LTD. [source] Stimulation of NMDA and AMPA glutamate receptors elicits distinct concentration dynamics of nitric oxide in rat hippocampal slicesHIPPOCAMPUS, Issue 7 2009J.G. Frade Abstract Nitric oxide (,NO) is an intercellular messenger implicated in memory formation and neurodegeneration in the hippocampus. Owing to its physical and chemical properties, the concentration dynamics of ,NO is a critical issue in determining its bioactivity as a signaling molecule. Its production is closely related to glutamate N -methyl- D -aspartate (NMDA) receptors, following a rise in intracellular calcium levels. However, that dependent on ,-amino-3-hydroxy-5-methylisoxazole-4-propionate (AMPA) receptors remains elusive and controversial, despite reports describing a role for these receptors in other brain regions, largely because of lack of quantitative and dynamic measurements of ,NO. Using a ,NO-selective microsensor inserted in the diffusional spread of ,NO in the CA1 region of rat hippocampal slices, we measured its real-time endogenous production, following activation of ionotropic glutamate receptors and under tissue physiological oxygen tension. Both NMDA and AMPA stimulation resulted in a concentration-dependent ,NO production but encompassing distinct kinetics for lag phases and slower rates of ,NO production were observed for AMPA stimulation. Robustness of the results was achieved instrumentally and pharmacologically, by means of nitric oxide synthase (NOS) inhibitors and antagonists of NMDA (D -(,)-2-amino-5-phosphonopentanoic acid, AP5) and AMPA (2,3-dioxo-6-nitro-1,2,3,4-tetrahydrobenzo[f]quinoxaline-7-sulfonamide, NBQX) receptors. When using glutamate as a stimulus, ,NO production was of lower magnitude in the presence of AP5 plus NBQX than with AP5 alone, suggesting that even when NMDA receptors are inhibited Ca2+ rises to levels to induce a peak of ,NO from the background. Whereas extracellular Ca2+ was required for the ,NO signals, Philanthotoxin-4,3,3 (PhTX-4,3,3) a toxin used to target Ca2+ -permeable AMPA receptors, attenuated ,NO production. These observations are interpreted on basis of a distinct coupling between the glutamate receptors and neuronal NOS. A role for Ca2+ -permeable AMPA receptors in the Ca2+ activation of neuronal NOS is suggested. © 2008 Wiley-Liss, Inc. [source] Polyribosomes are increased in spines of CA1 dendrites 2 h after the induction of LTP in mature rat hippocampal slicesHIPPOCAMPUS, Issue 1 2007Jennifer N. Bourne Abstract Enduring long-term potentiation (LTP) requires immediate protein synthesis, hence we assessed whether more polyribosomes are present in dendritic spines of mature hippocampal dendrites after the induction of LTP. Reconstructions from serial section transmission electron microscopy (sSTEM) revealed more dendritic polyribosomes 2 h posttetanus, relative to low-frequency stimulation (LFS). Polyribosomes were present in spines of all shapes with larger postsynaptic densities after 2 h, suggesting a coordinated local protein synthesis among many synapses to replenish proteins utilized during an earlier phase of LTP. © 2006 Wiley-Liss, Inc. [source] Muscarinic signaling is required for spike-pairing induction of long-term potentiation at rat Schaffer collateral-CA1 synapsesHIPPOCAMPUS, Issue 4 2004Scott V. Adams Abstract Cholinergic input from the basal forebrain and septum to the hippocampus is well known to be critical in learning and memory. Muscarinic induction of theta-frequency oscillations may synchronize pre- and postsynaptic firing and thereby enhance plasticity in the hippocampus. Previous studies have demonstrated that muscarinic activation facilitates long-term potentiation (LTP) induced with tetanus in vitro. In the present study, we tested the role of muscarinic receptor activity in the induction of LTP beyond effects on spike timing by using a spike-pairing (SP) method at Schaffer collateral-CA1 synapses in rat hippocampal slices. Pairings of pre- and postsynaptic action potentials (APs) have been shown to induce LTP when the presynaptic AP precedes the postsynaptic AP by 5,15 ms, but contribution of muscarinic co-activation has not been ruled out. We demonstrate that the mAChR antagonist atropine abolishes LTP induction by SP. Surprisingly, prolonged exposure to the mAChR agonist carbachol inhibits LTP induction by SP, perhaps because of receptor desensitization. These results demonstrate an essential role of cholinergic signaling in this form of hippocampal plasticity. © 2004 Wiley-Liss, Inc. [source] High-resolution real-time recording with microelectrode biosensors reveals novel aspects of adenosine release during hypoxia in rat hippocampal slicesJOURNAL OF NEUROCHEMISTRY, Issue 6 2003B. G. Frenguelli Abstract We have used improved miniaturized adenosine biosensors to measure adenosine release during hypoxia from within the CA1 region of rat hippocampal slices. These microelectrode biosensors record from the extracellular space in the vicinity of active synapses as they detect the synaptic field potentials evoked in area CA1 by stimulation of the afferent Schaffer collateral-commissural fibre pathway. Our new measurements demonstrate the rapid production of adenosine during hypoxia that precedes and accompanies depression of excitatory transmission within area CA1. Simultaneous measurement of adenosine release and synaptic transmission gives an estimated IC50 for adenosine on transmission in the low micromolar range. However, on reoxygenation, synaptic transmission recovers in the face of elevated extracellular adenosine and despite a post-hypoxic surge of adenosine release. This may indicate the occurrence of apparent adenosine A1 receptor desensitization during metabolic stress. In addition, adenosine release is unaffected by pharmacological blockade of glutamate receptors and shows depletion on repeated exposure to hypoxia. Our results thus suggest that adenosine release is not a consequence of excitotoxic glutamate release. The potential for adenosine A1 receptor desensitization during metabolic stress implies that its prevention may be beneficial in extending adenosine-mediated neuroprotection in a variety of clinically relevant conditions. [source] Neuroprotection with caspase-9 inhbition against in vitro and in vivo traumaJOURNAL OF NEUROCHEMISTRY, Issue 2002R. A. Wallis Objective:, To evaluate the neuroprotective efficacy of the cell-permeable caspase-9 inhibitor, LEHD-CHO, against in vitro and in vivo traumatic neuronal injury. Methods:, The neuroprotective potential of LEHD-CHO was assessed in vitro using rat hippocampal slices. CA1 orthodromic and antidromic population spike (PS) amplitude was monitored before and after fluid percussion injury in slices treated with or without LEHD-CHO. Final recovery of PS amplitude was assessed 95 min after trauma. Studies of in vivo neuroprotection with LEHD-CHO utilized a model of controlled cortical impact (CCI). Rats were given either LEHD-CHO (10 nmol icv) or an equal volume of vehicle at 5 min following CCI. Rats were perfused 24 h after CCI and brains were processed for histological examination. Results:, LEHD-CHO provided significant protection against loss of CA1 evoked response after fluid percussion. The EC50 for LEHD-CHO protection of CA1 orthodromic and antidromic PS amplitude against trauma was 2.1 ,m and 2.3 ,m. Protection extended to preservation of LTP after trauma. In vivo treatment with LEHD-CHO significantly decreased the appearance of eosinophilic cells in the CA1 region after CCI from 131 ± 23 cells in vehicle-treated animals to 24 ± 5 in LEHD-CHO treated animals. Extensive labelling with TUNEL staining was seen in vehicle-treated animals, whereas sections from LEHD-CHO treated animals demonstrated little staining. Conclusions:, These findings indicate that the caspase 9 inhibitor LHED-CHO provides concentration-dependent protection against in vitro CA1 neuronal injury, which extends to protection against in vivo CA1 injury from CCI. They further suggest that inhibition of caspase 9 may be a useful treatment strategy for traumatic brain injury. Acknowledgement:, Supported by VA Research and UCLA BIRC. [source] Acute Activation of Hippocampal Glucocorticoid Receptors Results in Different Waves of Gene Expression Throughout TimeJOURNAL OF NEUROENDOCRINOLOGY, Issue 4 2006M. C. Morsink Abstract Several aspects of hippocampal cell function are influenced by adrenal-secreted glucocorticoids in a delayed, genomic fashion. Previously, we used Serial Analysis of Gene Expression to identify glucocorticoid receptor (GR)-induced transcriptional changes in the hippocampus at a fixed time point. However, because changes in mRNA levels are transient and most likely precede the effects on hippocampal cell function, the aim of the current study was to assess the transcriptional changes in a broader time window by generating a time curve of GR-mediated gene expression changes. Therefore, we used rat hippocampal slices obtained from adrenalectomised rats, substituted in vivo with low corticosterone pellets, predominantly occupying the hippocampal mineralocorticoid receptors. To activate GR, slices were treated in vitro with a high (100 nM) dose of corticosterone and gene expression was profiled 1, 3 and 5 h after GR-activation. Using Affymetrix GeneChips, a striking pattern with different waves of gene expression was observed, shifting from exclusively down-regulated genes 1 h after GR-activation to both up and down regulated genes 3 h after GR-activation. After 5 h, the response was almost back to baseline. Additionally, real-time quantitative polymerase chain reaction was used for validation of a selection of responsive genes including genes involved in neurotransmission and synaptic plasticity such as the corticotropin releasing hormone receptor 1, monoamine oxidase A, LIMK1 and calmodulin 2. This permitted confirmation of GR-responsiveness of 15 out of 18 selected genes. In conclusion, direct activation of GR in hippocampal slices results in transient changes in gene expression. The pattern in which gene expression was modulated suggests that the fast genomic effects of glucocorticoids may be realised via transrepression, preceding a later wave of transactivation. Furthermore, we identified a number of interesting candidate genes which may underlie the glucocorticoid-mediated effects on hippocampal cell function. [source] Human immunodeficiency virus type 1 gp120 inhibits long-term potentiation via chemokine receptor CXCR4 in rat hippocampal slicesJOURNAL OF NEUROSCIENCE RESEARCH, Issue 3 2006Jun Dong Abstract Human immunodeficiency virus type 1 (HIV-1) infection in its human host often results in progressive dementia and encephalopathy in adults and children, respectively. The mechanisms underlying virus-induced neurocognitive dysfunction are not fully understood. However, several studies strongly suggest that secretory viral and immune products from infected brain macrophages and microglia affect the onset and tempo of disease. One critical neurotoxin among these secretory products is the HIV-1 envelope glycoprotein gp120. To better understand how HIV-1 gp120 may affect cognitive function, we studied its effects on long-term potentiation (LTP) in the CA1 region of rat hippocampus, the brain region best linked to learning and memory. Although no effects were observed on basal synaptic transmission, HIV-1 gp120 inhibited LTP in a concentration-dependent manner in the presence of ,-aminobutyric acid type A (GABAA) receptor antagonist. Heat-inactivated gp120 failed to block LTP. The HIV-1 gp120-mediated LTP inhibition was blocked by T140, a chemokine receptor CXCR4 antagonist, demonstrating gp120 inhibition of LTP via CXCR4. HIV-1 gp120 V3 loop peptides mimicked the inhibitory effects of HIV-1 gp120 protein on LTP. Monoclonal antibodies against the V3 loop epitope KRIHI eliminated the HIV-1 gp120 effects on LTP. These results further underscore the importance of HIV-1 gp120 in the pathogenesis of HIV-1-associated cognitive impairments seen during progressive viral infection. © 2006 Wiley-Liss, Inc. [source] Simultaneous diffusion MRI measurements from multiple perfused rat hippocampal slicesMAGNETIC RESONANCE IN MEDICINE, Issue 3 2002Timothy M. Shepherd Abstract Rat brain slices provide a controllable tissue model in which to investigate the biophysical basis of diffusion-weighted magnetic resonance (MR) signal changes observed clinically in nervous tissue after ischemic injury. This study describes a new multislice perfusion chamber that allows for the simultaneous acquisition of diffusion-weighted MR images from multiple perfused rat hippocampal slices (eight slices in the present study). These images had a signal-to-noise ratio (SNR) of 48 ± 3 at b = 8080 s/mm2, which was sufficient to analyze the multicomponent diffusion properties of water in rat hippocampal slices. The tissue water diffusion parameters (ffast = 0.527 ± 0.041, Dfast = 1.268 ± 0.087 × 10,3 mm2/s, and Dslow = 0.060 ± 0.003 × 10,3 mm2/s) were stable for at least 8 hr after slice procurement (ANOVA, P > 0.05), suggesting that it may be possible to study the acute temporal evolution of diffusion changes in multiple brain slices following experimental perturbation. Magn Reson Med 48:565,569, 2002. © 2002 Wiley-Liss, Inc. [source] Anticonvulsant and antiepileptic actions of 2-deoxy-D-glucose in epilepsy models,ANNALS OF NEUROLOGY, Issue 4 2009Carl E. Stafstrom MD Objective Conventional anticonvulsants reduce neuronal excitability through effects on ion channels and synaptic function. Anticonvulsant mechanisms of the ketogenic diet remain incompletely understood. Because carbohydrates are restricted in patients on the ketogenic diet, we evaluated the effects of limiting carbohydrate availability by reducing glycolysis using the glycolytic inhibitor 2-deoxy-D-glucose (2DG) in experimental models of seizures and epilepsy. Methods Acute anticonvulsant actions of 2DG were assessed in vitro in rat hippocampal slices perfused with 7.5mM [K+]o, 4-aminopyridine, or bicuculline, and in vivo against seizures evoked by 6Hz stimulation in mice, audiogenic stimulation in Fring's mice, and maximal electroshock and subcutaneous pentylenetetrazol (Metrazol) in rats. Chronic antiepileptic effects of 2DG were evaluated in rats kindled from olfactory bulb or perforant path. Results 2DG (10mM) reduced interictal epileptiform bursts induced by 7.5mM [K+]o, 4-aminopyridine, and bicuculline, and electrographic seizures induced by high [K+]o in CA3 of hippocampus. 2DG reduced seizures evoked by 6Hz stimulation in mice (effective dose [ED]50 = 79.7mg/kg) and audiogenic stimulation in Fring's mice (ED50 = 206.4mg/kg). 2DG exerted chronic antiepileptic action by increasing afterdischarge thresholds in perforant path (but not olfactory bulb) kindling and caused a twofold slowing in progression of kindled seizures at both stimulation sites. 2DG did not protect against maximal electroshock or Metrazol seizures. Interpretation The glycolytic inhibitor 2DG exerts acute anticonvulsant and chronic antiepileptic actions, and has a novel pattern of effectiveness in preclinical screening models. These results identify metabolic regulation as a potential therapeutic target for seizure suppression and modification of epileptogenesis. Ann Neurol 2009;65:435,448. 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