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Sample records for ca3 hippocampal slices

  1. Modulation by adenine nucleotides of epileptiform activity in the CA3 region of rat hippocampal slices

    PubMed Central

    Ross, F M; Brodie, M J; Stone, T W

    1998-01-01

    Hippocampal slices (450 μm) generate epileptiform bursts of an interictal nature when perfused with a zero magnesium medium containing 4-aminopyridine (50 μM). The effect of adenine nucleotides on this activity was investigated.ATP and adenosine depressed this epileptiform activity in a concentration-dependent manner, with both purines being equipotent at concentrations above 10 μM.Adenosine deaminase 0.2 u ml−1, a concentration that annuls the effect of adenosine (50 μM), did not significantly alter the depression of activity caused by ATP (50 μM).8-Cyclopentyl-1, 3-dimethylxanthine (CPT), an A1 receptor antagonist, enhanced the discharge rate significantly and inhibited the depressant effect of both ATP and adenosine such that the net effect of ATP or adenosine plus CPT was excitatory.Several ATP analogues were also tested: α, β-methyleneATP (α, β-meATP), 2-methylthioATP (2-meSATP) and uridine triphosphate (UTP). Only α, β-meATP (10 μM) produced an increase in the frequency of spontaneous activity which suggests a lack of involvement of P2Y or P2U receptors.Suramin and pyridoxalphosphate-6-azophenyl-2′, 4′-disulphonic acid (PPADS), P2 receptor antagonists, failed to inhibit the depression produced by ATP (50 μM). The excitatory effect of α, β-meATP (10 μM) was inhibited by suramin (50 μM) and PPADS (5 μM).ATP therefore depresses epileptiform activity in this model in a manner which is not consistent with the activation of known P1 or P2 receptors, suggesting the involvement of a xanthine-sensitive nucleotide receptor. The results are also indicative of an excitatory P2X receptor existing in the hippocampal CA3 region. PMID:9484856

  2. Electrical and Pharmacological Stimuli Reveal a Greater Susceptibility for CA3 Network Excitability in Hippocampal Slices from Aged vs. Adult Fischer 344 Rats

    PubMed Central

    Kanak, Daniel J.; Jones, Ryan T.; Tokhi, Ashish; Willingham, Amy L.; Zaveri, Hitten P.; Rose, Gregory M.; Patrylo, Peter R.

    2011-01-01

    Clinical data and experimental studies in rats have shown that the aged CNS is more susceptible to the proconvulsive effects of the excitotoxic glutamate analogues kainate (KA) and domoate (DA), which bind high-affinity receptors localized at mossy fiber (MF) synapses in the CA3 subregion of the hippocampus. Although decreased renal clearance appears to play a role in the hypersensitivity of the aged hippocampus to systemically-administered DA, it is unclear if the excitability of the CA3 network is also altered with age. Therefore, this study monitored CA3 field potential activity in hippocampal slices from aged and adult male Fischer 344 rats in response to electrical and pharmacological network stimulation targeted to the MF-CA3 circuit. Network challenges with repetitive hilar stimulation or bath application of nanomolar concentrations of KA more readily elicited excitable network activity (e.g. population spike facilitation, multiple population spikes, and epileptiform bursts) in slices from aged vs. adult rats, although basal network excitability was comparable between age groups. Additionally, exposure to 200 nM KA often abolished epileptiform activity and revealed theta or gamma oscillations instead. However, slices from aged rats were less sensitive to the rhythmogenic effects of 200 nM KA. Taken together, these findings suggest that aging decreases the capacity of the CA3 network to constrain the spread of excitability during focal excitatory network challenges. PMID:22396884

  3. FK960, a novel potential anti-dementia drug, augments long-term potentiation in mossy fiber-CA3 pathway of guinea-pig hippocampal slices.

    PubMed

    Matsuoka, N; Satoh, M

    1998-06-01

    Our previous studies have demonstrated that FK960 (FR59960; N-(4-acetyl-1-piperazinyl)-p-fluorobenzamide monohydrate), a novel antidementia piperazine derivative, exerts beneficial effects on memory deficits in various animal models of amnesia in rats [M. Yamazaki, N. Matsuoka, N. Maeda, Y. Ohkubo, I. Yamaguchi, FK960 N-(4-acetyl-1-piperazinyl)-p-fluorobenzamide monohydrate ameliorates the memory deficits in rats through a novel mechanism of action, J. Pharmacol. Exp. Ther., 279 (1996) 1157-1173.] and in rhesus monkeys [N. Matsuoka, T.G. Aigner, FK960 [N-(4-acetyl-1-piperazinyl)-p-fluorobenzamide monohydrate], a novel potential antidementia drug, improves visual recognition memory in rhesus monkeys: comparison with physostigmine, J. Pharmacol. Exp. Ther., 280 (1997) 1201-1209]. To clarify the synaptic mechanisms of its antiamnesic action, FK960 was investigated for its effects on the development of long-term potentiation (LTP) in guinea-pig hippocampal slices. The magnitude of LTP of population spike recorded in CA3 pyramidal neurons was significantly augmented by perfusing FK960 (10-9-10-6 M) for 25 min before and during tetanic stimulation of the mossy fibers, whereas the basal amplitude of population spikes before tetanus was hardly affected by the drug. The dose-response curve was bell-shaped with a maximal augmentation at 10-7 M. Scopolamine (10-6 M) per se had little effect on the magnitude of LTP in the mossy fiber-CA3 pathway, but significantly attenuated its enhancement by FK960 (10-7 M). In hippocampal slices from animals treated with cysteamine (200 mg/kg, s.c.), which was shown to deplete the hippocampal somatostatin, FK960 (10-7 M) hardly affected the LTP. These results suggest that FK960 enhances the magnitude of LTP in the mossy fiber-CA3 pathway through an activation of the cholinergic-somatostatinergic link in the hippocampal formation. Furthermore, it can be postulated that the drug regulates the cognitive function by modulating directly synaptic

  4. Topographic specificity of functional connections from hippocampal CA3 to CA1

    NASA Astrophysics Data System (ADS)

    Brivanlou, Iman H.; Dantzker, Jami L. M.; Stevens, Charles F.; Callaway, Edward M.

    2004-02-01

    The hippocampus is a cortical region thought to play an important role in learning and memory. Most of our knowledge about the detailed organization of hippocampal circuitry responsible for these functions is derived from anatomical studies. These studies present an incomplete picture, however, because the functional character and importance of connections are often not revealed by anatomy. Here, we used a physiological method (photostimulation with caged glutamate) to probe the fine pattern of functional connectivity between the CA3 and CA1 subfields in the mouse hippocampal slice preparation. We recorded intracellularly from CA1 and CA3 pyramidal neurons while scanning with photostimulation across the entire CA3 subfield with high spatial resolution. Our results show that, at a given septotemporal level, nearby CA1 neurons receive synaptic inputs from neighboring CA3 neurons. Thus, the CA3 to CA1 mapping preserves neighbor relations.

  5. Enhanced excitability of hippocampal mossy fibers and CA3 neurons under dietary zinc deficiency.

    PubMed

    Takeda, Atsushi; Yamada, Kohei; Minami, Akira; Nagano, Tetsuo; Oku, Naoto

    2005-02-01

    On the basis of the evidence that susceptibility to kainate-induced seizures is enhanced by zinc deficiency and that glutamate concentrations in hippocampal extracellular fluid are excessively increased during seizures, excitability of hippocampal mossy fibers and CA3 neurons was examined using hippocampal slices, which were prepare from mice fed a zinc-deficient diet for 4 weeks. The spatio-temporal dynamics of zinc and calcium was monitored using their indicators, membrane-impermeable ZnAF-2 and membrane-permeable fura-2 AM, respectively. When the molecular layer of dentate gyrus was stimulated with 100mM KCl for 1s, the increased percentages of extracellular zinc in the stratum lucidum and CA3 pyramidal cell layer were higher in zinc-deficient mice than in the control mice, implying that glutamate release from the mossy fibers of the dentate granular cells is enhanced by zinc deficiency. Judging from the increased percentages, however, the amount of zinc released was estimated to be less in zinc-deficient mice. On the other hand, the basal calcium concentrations in the stratum lucidum and CA3 pyramidal cell layer detected with fura-2 were higher in zinc-deficient mice than in the control mice, indicating that hippocampal calcium homeostasis is affected by zinc deficiency. Furthermore, the increased percentage of intracellular calcium in the stratum lucidum by stimulation with high K+ was enhanced by the zinc deficiency. The alteration of hippocampal calcium homeostasis seems to enhance excitability of dentate granular cells in zinc deficiency, following by an enhanced excitability of postsynaptic structures in CA3 neurons. PMID:15716032

  6. Neurosteroids differentially modulate fast and slow interictal discharges in the hippocampal CA3 area

    PubMed Central

    Herrington, Rochelle; Levesque, Maxime; Avoli, Massimo

    2016-01-01

    Two types of spontaneous interictal discharge, identified as fast and slow events, can be recorded from the hippocampal CA3 area in rat brain slices during application of 4-aminopyridine (4AP) (50 μM). Here, we addressed how neurosteroids modulate the occurrence of these interictal events and of the associated high-frequency oscillations (HFOs) (ripples, 80–200 Hz; fast ripples, 250–500 Hz). Under control conditions (i.e. during 4AP application), ripples and fast ripples were detected in 12.3 and 17.5% of fast events, respectively; in contrast, the majority of slow events (> 98%) did not co-occur with HFOs. Application of 0.1, 1 or 5 μM allotetrahydrodeoxycorticosterone (THDOC) to 4AP-treated slices caused a dose-dependent decrease in the duration of the fast events and an increase in the occurrence of ripples, but not fast ripples; in contrast, the duration of slow events increased. THDOC potentiated the slow events that were recorded during pharmacological blockade of glutamatergic transmission, but had no effect on interictal discharges occurring during GABAA receptor antagonism. These results demonstrate that potentiation of GABAA receptor-mediated signaling by THDOC differentially affects slow and fast interictal discharges; these differences may provide insights into how hyperexcitable activity is influenced by neurosteroids. PMID:25471484

  7. Excitation/inhibition imbalance and impaired synaptic inhibition in hippocampal area CA3 of Mecp2 knockout mice.

    PubMed

    Calfa, Gaston; Li, Wei; Rutherford, John M; Pozzo-Miller, Lucas

    2015-02-01

    Rett syndrome (RTT) is a neurodevelopment disorder associated with intellectual disabilities and caused by loss-of-function mutations in the gene encoding the transcriptional regulator Methyl-CpG-binding Protein-2 (MeCP2). Neuronal dysfunction and changes in cortical excitability occur in RTT individuals and Mecp2-deficient mice, including hippocampal network hyperactivity and higher frequency of spontaneous multiunit spikes in the CA3 cell body layer. Here, we describe impaired synaptic inhibition and an excitation/inhibition (E/I) imbalance in area CA3 of acute slices from symptomatic Mecp2 knockout male mice (referred to as Mecp2(-/y) ). The amplitude of TTX-resistant miniature inhibitory postsynaptic currents (mIPSC) was smaller in CA3 pyramidal neurons of Mecp2(-/y) slices than in wildtype controls, while the amplitude of miniature excitatory postsynaptic currents (mEPSC) was significantly larger in Mecp2(-/y) neurons. Consistently, quantitative confocal immunohistochemistry revealed significantly lower intensity of the alpha-1 subunit of GABAA Rs in the CA3 cell body layer of Mecp2(-/y) mice, while GluA1 puncta intensities were significantly higher in the CA3 dendritic layers of Mecp2(-/y) mice. In addition, the input/output (I/O) relationship of evoked IPSCs had a shallower slope in CA3 pyramidal neurons Mecp2(-/y) neurons. Consistent with the absence of neuronal degeneration in RTT and MeCP2-based mouse models, the density of parvalbumin- and somatostatin-expressing interneurons in area CA3 was not affected in Mecp2(-/y) mice. Furthermore, the intrinsic membrane properties of several interneuron subtypes in area CA3 were not affected by Mecp2 loss. However, mEPSCs are smaller and less frequent in CA3 fast-spiking basket cells of Mecp2(-/y) mice, suggesting an impaired glutamatergic drive in this interneuron population. These results demonstrate that a loss-of-function mutation in Mecp2 causes impaired E/I balance onto CA3 pyramidal neurons, leading to a

  8. Segmental cable evaluation of somatic transients in hippocampal neurons (CA1, CA3, and dentate).

    PubMed Central

    Turner, D A

    1984-01-01

    This study describes a detailed cable model of neuronal structure, which can predict the effects of discrete transient inputs. Neurons in in vitro hippocampal slices (CA1 and CA3 pyramidal cells and dentate granule neurons; n = 4 each) were physiologically characterized and stained with horseradish peroxidase (HRP). The HRP morphology was approximated with numerous small segments. The cable model included both these segments and spatially dispersed dendritic spines. The transient response function at the soma of the segmental model was numerically derived, and charging responses to simulated current inputs were computed. These simulations were compared with the physiological charging responses from the somatic penetrations, using an analysis of the charging time constants (tau i) and intercepts. The time constant ratio (tau 0/tau 1) did not significantly differ between the observed and simulated responses. A second index of comparison was the equivalent cylinder electrotonic length (L), which was derived using only the tau i values and their intercepts. The L values also did not differ significantly between the observed and simulated transients and averaged 0.91 length constant. Thus, using criteria based only on analysis of charging responses, the segmental cable model recreated accurately the observed transients at the soma. The equivalent cylinder model (with a lumped soma) could also adequately simulate the observed somatic transients, using the same criteria. However, the hippocampal neurons (particularly the pyramidal cells) did not appear to satisfy the equivalent cylinder assumption anatomically. Thus, the analysis of somatic charging transients alone may not be sufficient to discriminate between the two models of hippocampal neurons. Anatomical evidence indicates that, particularly for discrete dendritic inputs, the detailed segmental model may be more appropriate than the equivalent cylinder model. PMID:6743759

  9. Cannabinoids attenuate hippocampal gamma oscillations by suppressing excitatory synaptic input onto CA3 pyramidal neurons and fast spiking basket cells

    PubMed Central

    Holderith, Noémi; Németh, Beáta; Papp, Orsolya I; Veres, Judit M; Nagy, Gergő A; Hájos, Norbert

    2011-01-01

    Abstract CB1 cannabinoid receptor (CB1R) activation by exogenous ligands can impair memory processes, which critically depend on synchronous neuronal activities that are temporarily structured by oscillations. In this study, we aimed to reveal the mechanisms underlying the cannabinoid-induced decrease in gamma oscillations. We first verified that cannabinoids (CP55,940 and WIN55,212-2) readily suppressed carbachol-induced gamma oscillations in the CA3 region of hippocampal slices via activation of CB1Rs. The cannabinoid-induced decrease in the peak power of oscillations was accompanied by reduced and less precise firing activity in CA3 pyramidal cells and fast spiking basket cells. By examining the cannabinoid sensitivity of synaptic inputs we found that the amplitude of evoked excitatory postsynaptic currents was significantly suppressed upon CB1R activation in both CA3 pyramidal cells and fast spiking basket cells. In contrast, evoked inhibitory postsynaptic currents in CA3 pyramidal cells were unaltered. Furthermore, we observed that a CB1R agonist-induced decrease in the oscillation power at the beginning of the drug application was accompanied primarily by the reduced discharge of fast spiking basket cells, while pyramidal cell firing was unaltered. This result implies that the dampening of cholinergically induced gamma oscillations in the hippocampus by cannabinoids can be explained by a reduced excitatory input predominantly onto fast spiking basket cells, which leads to a reduction in neuronal firing frequency and precision, and thus to smaller field potentials. In addition, we uncovered that the spontaneously occurring sharp wave-ripple activities in hippocampal slices could also be suppressed by CB1R activation suggesting that cannabinoids profoundly reduce the intrinsically generated oscillatory activities at distinct frequencies in CA3 networks by reducing synaptic neurotransmission. PMID:21859823

  10. Synaptic mechanisms of pattern completion in the hippocampal CA3 network.

    PubMed

    Guzman, Segundo Jose; Schlögl, Alois; Frotscher, Michael; Jonas, Peter

    2016-09-01

    The hippocampal CA3 region plays a key role in learning and memory. Recurrent CA3-CA3 synapses are thought to be the subcellular substrate of pattern completion. However, the synaptic mechanisms of this network computation remain enigmatic. To investigate these mechanisms, we combined functional connectivity analysis with network modeling. Simultaneous recording from up to eight CA3 pyramidal neurons revealed that connectivity was sparse, spatially uniform, and highly enriched in disynaptic motifs (reciprocal, convergence, divergence, and chain motifs). Unitary connections were composed of one or two synaptic contacts, suggesting efficient use of postsynaptic space. Real-size modeling indicated that CA3 networks with sparse connectivity, disynaptic motifs, and single-contact connections robustly generated pattern completion. Thus, macro- and microconnectivity contribute to efficient memory storage and retrieval in hippocampal networks. PMID:27609885

  11. A quantitative theory of the functions of the hippocampal CA3 network in memory.

    PubMed

    Rolls, Edmund T

    2013-01-01

    A quantitative computational theory of the operation of the hippocampal CA3 system as an autoassociation or attractor network used in episodic memory system is described. In this theory, the CA3 system operates as a single attractor or autoassociation network to enable rapid, one-trial, associations between any spatial location (place in rodents, or spatial view in primates) and an object or reward, and to provide for completion of the whole memory during recall from any part. The theory is extended to associations between time and object or reward to implement temporal order memory, also important in episodic memory. The dentate gyrus (DG) performs pattern separation by competitive learning to produce sparse representations suitable for setting up new representations in CA3 during learning, producing for example neurons with place-like fields from entorhinal cortex grid cells. The dentate granule cells produce by the very small number of mossy fiber (MF) connections to CA3 a randomizing pattern separation effect important during learning but not recall that separates out the patterns represented by CA3 firing to be very different from each other, which is optimal for an unstructured episodic memory system in which each memory must be kept distinct from other memories. The direct perforant path (pp) input to CA3 is quantitatively appropriate to provide the cue for recall in CA3, but not for learning. Tests of the theory including hippocampal subregion analyses and hippocampal NMDA receptor knockouts are described, and support the theory. PMID:23805074

  12. A quantitative theory of the functions of the hippocampal CA3 network in memory

    PubMed Central

    Rolls, Edmund T.

    2013-01-01

    A quantitative computational theory of the operation of the hippocampal CA3 system as an autoassociation or attractor network used in episodic memory system is described. In this theory, the CA3 system operates as a single attractor or autoassociation network to enable rapid, one-trial, associations between any spatial location (place in rodents, or spatial view in primates) and an object or reward, and to provide for completion of the whole memory during recall from any part. The theory is extended to associations between time and object or reward to implement temporal order memory, also important in episodic memory. The dentate gyrus (DG) performs pattern separation by competitive learning to produce sparse representations suitable for setting up new representations in CA3 during learning, producing for example neurons with place-like fields from entorhinal cortex grid cells. The dentate granule cells produce by the very small number of mossy fiber (MF) connections to CA3 a randomizing pattern separation effect important during learning but not recall that separates out the patterns represented by CA3 firing to be very different from each other, which is optimal for an unstructured episodic memory system in which each memory must be kept distinct from other memories. The direct perforant path (pp) input to CA3 is quantitatively appropriate to provide the cue for recall in CA3, but not for learning. Tests of the theory including hippocampal subregion analyses and hippocampal NMDA receptor knockouts are described, and support the theory. PMID:23805074

  13. Trafficking of astrocytic vesicles in hippocampal slices

    SciTech Connect

    Potokar, Maja; Kreft, Marko; Celica Biomedical Center, Technology Park 24, 1000 Ljubljana ; Lee, So-Young; Takano, Hajime; Haydon, Philip G.; Zorec, Robert; Celica Biomedical Center, Technology Park 24, 1000 Ljubljana

    2009-12-25

    The increasingly appreciated role of astrocytes in neurophysiology dictates a thorough understanding of the mechanisms underlying the communication between astrocytes and neurons. In particular, the uptake and release of signaling substances into/from astrocytes is considered as crucial. The release of different gliotransmitters involves regulated exocytosis, consisting of the fusion between the vesicle and the plasma membranes. After fusion with the plasma membrane vesicles may be retrieved into the cytoplasm and may continue to recycle. To study the mobility implicated in the retrieval of secretory vesicles, these structures have been previously efficiently and specifically labeled in cultured astrocytes, by exposing live cells to primary and secondary antibodies. Since the vesicle labeling and the vesicle mobility properties may be an artifact of cell culture conditions, we here asked whether the retrieving exocytotic vesicles can be labeled in brain tissue slices and whether their mobility differs to that observed in cell cultures. We labeled astrocytic vesicles and recorded their mobility with two-photon microscopy in hippocampal slices from transgenic mice with fluorescently tagged astrocytes (GFP mice) and in wild-type mice with astrocytes labeled by Fluo4 fluorescence indicator. Glutamatergic vesicles and peptidergic granules were labeled by the anti-vesicular glutamate transporter 1 (vGlut1) and anti-atrial natriuretic peptide (ANP) antibodies, respectively. We report that the vesicle mobility parameters (velocity, maximal displacement and track length) recorded in astrocytes from tissue slices are similar to those reported previously in cultured astrocytes.

  14. Involvement of the dopaminergic system in the consolidation of fear conditioning in hippocampal CA3 subregion.

    PubMed

    Wen, Jia-Ling; Xue, Li; Wang, Run-Hua; Chen, Zi-Xiang; Shi, Yan-Wei; Zhao, Hu

    2015-02-01

    The hippocampus, the primary brain structure related to learning and memory, receives sparse but comprehensive dopamine innervations and contains dopamine D1 and D2 receptors. Systematic hippocampal dopaminergic dysfunction can cause deficits in spatial working memory and impair consolidation of contextual fear memories. CA3 is involved in the rapid acquisition of new memories and has extensive nerve fibre connections with other brain structures such as CA1, the amygdala, and the medial prefrontal cortex (mPFC). A bidirectional fibrous connection between CA3 and the amygdala reflects the importance of CA3 in fear conditioning. The present study evaluated the effects of a 6-OHDA lesion in CA3 on the acquisition and expression of conditioned fear. The results showed CA3 involvement in the expression but not the acquisition of conditioned fear. Injection of SCH23390 and quinpirole into the bilateral CA3 attenuated a conditioned fear-related freezing response, whereas SKF38393 and sulpiride were not associated with this effect. The present study found that a 6-OHDA lesion in CA3 up-regulated the expression of GluR1 in BLA and down-regulated NR2B in CA1 and the basolateral amygdala (BLA). Our data suggest that dopamine depletion in hippocampal subdivision CA3 may not be necessary for the acquisition of conditioned fear, but the expression of conditioned fear is likely dependent on the integrity of mesohippocampal dopaminergic connections. It is probable that both D1 and D2 dopaminergic receptors modulate the expression of conditioned fear. Changes in the expression of NR2B and GluR1 indicate that CA3 may modulate the activities of other brain structures. PMID:25446753

  15. SNAP-25 in hippocampal CA3 region is required for long-term memory formation

    SciTech Connect

    Hou Qiuling; Gao Xiang; Lu Qi; Zhang Xuehan; Tu Yanyang; Jin Meilei; Zhao Guoping; Yu Lei; Jing Naihe; Li Baoming . E-mail: bmli@fudan.edu.cn

    2006-09-08

    SNAP-25 is a synaptosomal protein of 25 kDa, a key component of synaptic vesicle-docking/fusion machinery, and plays a critical role in exocytosis and neurotransmitter release. We previously reported that SNAP-25 in the hippocampal CA1 region is involved in consolidation of contextual fear memory and water-maze spatial memory (Hou et al. European J Neuroscience, 20: 1593-1603, 2004). SNAP-25 is expressed not only in the CA1 region, but also in the CA3 region, and the SNAP-25 mRNA level in the CA3 region is higher than in the CA1 region. Here, we provide evidence that SNAP-25 in the CA3 region is also involved in learning/memory. Intra-CA3 infusion of SNAP-25 antisense oligonucleotide impaired both long-term contextual fear memory and water-maze spatial memory, with short-term memory intact. Furthermore, the SNAP-25 antisense oligonucleotide suppressed the long-term potentiation (LTP) of field excitatory post-synaptic potential (fEPSP) in the mossy-fiber pathway (DG-CA3 pathway), with no effect on paired-pulse facilitation of the fEPSP. These results are consistent with the notion that SNAP-25 in the hippocampal CA3 region is required for long-term memory formation.

  16. Encoding, Consolidation, and Retrieval of Contextual Memory: Differential Involvement of Dorsal CA3 and CA1 Hippocampal Subregions

    ERIC Educational Resources Information Center

    Daumas, Stephanie; Halley, Helene; Frances, Bernard; Lassalle, Jean-Michel

    2005-01-01

    Studies on human and animals shed light on the unique hippocampus contributions to relational memory. However, the particular role of each hippocampal subregion in memory processing is still not clear. Hippocampal computational models and theories have emphasized a unique function in memory for each hippocampal subregion, with the CA3 area acting…

  17. Distinct Dendritic Arborization and In Vivo Firing Patterns of Parvalbumin-Expressing Basket Cells in the Hippocampal Area CA3

    PubMed Central

    Tukker, John J.; Lasztóczi, Bálint; Katona, Linda; Roberts, J. David B.; Pissadaki, Eleftheria K.; Dalezios, Yannis; Márton, László; Zhang, Limei; Klausberger, Thomas; Somogyi, Peter

    2015-01-01

    Hippocampal CA3 area generates temporally structured network activity such as sharp waves and gamma and theta oscillations. Parvalbumin-expressing basket cells, making GABAergic synapses onto cell bodies and proximal dendrites of pyramidal cells, control pyramidal cell activity and participate in network oscillations in slice preparations, but their roles in vivo remain to be tested. We have recorded the spike timing of parvalbumin-expressing basket cells in areas CA2/3 of anesthetized rats in relation to CA3 putative pyramidal cell firing and activity locally and in area CA1. During theta oscillations, CA2/3 basket cells fired on the same phase as putative pyramidal cells, but, surprisingly, significantly later than downstream CA1 basket cells. This indicates a distinct modulation of CA3 and CA1 pyramidal cells by basket cells, which receive different inputs. We observed unexpectedly large dendritic arborization of CA2/3 basket cells in stratum lacunosum moleculare (33% of length, 29% surface, and 24% synaptic input from a total of ~35,000), different from the dendritic arborizations of CA1 basket cells. Area CA2/3 basket cells fired phase locked to both CA2/3 and CA1 gamma oscillations, and increased firing during CA1 sharp waves, thus supporting the role of CA3 networks in the generation of gamma oscillations and sharp waves. However, during ripples associated with sharp waves, firing of CA2/3 basket cells was phase locked only to local but not CA1 ripples, suggesting the independent generation of fast oscillations by basket cells in CA1 and CA2/3. The distinct spike timing of basket cells during oscillations in CA1 and CA2/3 suggests differences in synaptic inputs paralleled by differences in dendritic arborizations. PMID:23595740

  18. Pattern separation of emotional information in hippocampal dentate and CA3.

    PubMed

    Leal, Stephanie L; Tighe, Sarah K; Jones, Craig K; Yassa, Michael A

    2014-09-01

    Emotional arousal, mediated by the amygdala, is known to modulate episodic memories stored by the hippocampus, a region involved in pattern separation (the process by which similar representations are independently stored). While emotional modulation and pattern separation have been examined independently, this study attempts to link the two areas of research to propose an alternative account for how emotion modulates episodic memory. We used an emotional discrimination task designed to tax pattern separation of emotional information by concurrently varying emotional valence and similarity of stimuli. To examine emotional modulation of memory at the level of hippocampal subfields, we used high-resolution fMRI (1.5 mm isotropic) of the medial temporal lobe. Consistent with prior reports, we observed engagement of the hippocampal dentate gyrus (DG) and CA3 during accurate discrimination of highly similar items (behavioral correlate of pattern separation). Furthermore, we observed an emotional modulation of this signal (negative > neutral) specific to trials on which participants accurately discriminated similar emotional items. The amygdala was also modulated by emotion, regardless of the accuracy of discrimination. Additionally, we found aberrant amygdala-hippocampal network activity in a sample of adults with depressive symptoms. In this sample, amygdala activation was enhanced and DG/CA3 activation was diminished during emotional discrimination compared to those without depressive symptoms. Depressive symptom severity was also negatively correlated with DG/CA3 activity. This study suggests a novel mechanistic account for how emotional information is processed by hippocampal subfields as well as how this network may be altered in mood disorders. PMID:24796287

  19. Unstable periodic orbits in human epileptic hippocampal slices.

    PubMed

    Pen-Ning Yu; Min-Chi Hsiao; Dong Song; Liu, Charles Y; Heck, Christi N; Millett, David; Berger, Theodore W

    2014-01-01

    Inter-ictal activity is studied in hippocampal slices resected from patients with epilepsy using local field potential recording. Inter-ictal activity in the dentate gyrus (DG) is induced by high-potassium (8 mM), low-magnesium (0.25 mM) aCSF with additional 100 μM 4-aminopyridine(4-AP). The dynamics of the inter-ictal activity is investigated by developing the first return map with inter-pulse intervals. Unstable periodic orbits (UPOs) are detected in the hippocampal slice at the DG area according to both the topological recurrence method and the periodic orbit transform method. Surrogate analysis suggests the presence of UPOs in hippocampal slices from patients with epilepsy. This finding also suggests that inter-ictal activity is a chaotic system and will allow us to apply chaos control techniques to manipulate inter-ictal activity. PMID:25571314

  20. OLM interneurons differentially modulate CA3 and entorhinal inputs to hippocampal CA1 neurons

    PubMed Central

    Leão, Richardson N; Mikulovic, Sanja; Leão, Katarina E; Munguba, Hermany; Gezelius, Henrik; Enjin, Anders; Patra, Kalicharan; Eriksson, Anders; Loew, Leslie M.; Tort, Adriano BL; Kullander, Klas

    2012-01-01

    The vast diversity of GABAergic interneurons is believed to endow hippocampal microcircuits with the required flexibility for memory encoding and retrieval. However, dissection of the functional roles of defined interneuron types have been hampered by the lack of cell specific tools. Here we report a precise molecular marker for a population of hippocampal GABAergic interneurons known as oriens lacunosum-moleculare (OLM) cells. By combining novel transgenic mice and optogenetic tools, we demonstrate that OLM cells have a key role in gating the information flow in CA1, facilitating the transmission of intrahippocampal information (from CA3) while reducing the influence of extrahippocampal inputs (from the entorhinal cortex). We further demonstrate that OLM cells are interconnected by gap junctions, receive direct cholinergic inputs from subcortical afferents, and account for the effect of nicotine on synaptic plasticity of the Schaffer collateral pathway. Our results suggest that acetylcholine acting through OLM cells can control the mnemonic processes executed by the hippocampus. PMID:23042082

  1. Rapid manifestation of reactive astrogliosis in acute hippocampal brain slices

    PubMed Central

    Takano, Takahiro; He, Wei; Han, Xiaoning; Wang, Fushun; Xu, Qiwu; Wang, Xiaohai; Oberheim Bush, Nancy Ann; Cruz, Nancy; Dienel, Gerald A.; Nedergaard, Maiken

    2014-01-01

    A flurry of studies over the past decade has shown that astrocytes play a more active role in neural function than previously recognized. Hippocampal slices prepared from young rodent pups have served as a popular model for studying the pathways by which astrocytes participate in synaptic transmission. It is, however, not known how well astrocytes tolerate traumatic injury and hypoxia, which are unavoidable when preparing acute slices. We here show that astrocytes exhibit striking changes in expression of several receptors and structural proteins, including re-expression of the developmental marker nestin within 90 min following preparation of live vibratome slices. Moreover, immunoelectron microscopy showed a 2.7-fold loss of astrocytic processes in acute hippocampal slices prepared from GFAP-GFP reporter mice. A sharp decrease in the number of mitochondria was also noted in acute slices, concurrently with an increase in mitochondrial size. Glycogen content decreased 3-fold upon slice preparation and did not recover despite stable recordings of field EPSC. Analysis of Ca2+ signaling showed that astrocytic responses to purine receptor and mGluR5 agonists differed in slice vs. in vivo. These observations suggest that the functional properties and the fine structure of astrocytes in slices may be reflective of early stages of reactive gliosis and should be confirmed in vivo when possible. PMID:24272704

  2. Rapid manifestation of reactive astrogliosis in acute hippocampal brain slices.

    PubMed

    Takano, Takahiro; He, Wei; Han, Xiaoning; Wang, Fushun; Xu, Qiwu; Wang, Xiaohai; Oberheim Bush, Nancy Ann; Cruz, Nancy; Dienel, Gerald A; Nedergaard, Maiken

    2014-01-01

    A flurry of studies over the past decade has shown that astrocytes play a more active role in neural function than previously recognized. Hippocampal slices prepared from young rodent pups have served as a popular model for studying the pathways by which astrocytes participate in synaptic transmission. It is, however, not known how well astrocytes tolerate traumatic injury and hypoxia, which are unavoidable when preparing acute slices. We here showed that astrocytes exhibit striking changes in expression of several receptors and structural proteins, including re-expression of the developmental marker nestin within 90 min following preparation of live vibratome slices. Moreover, immunoelectron microscopy showed a 2.7-fold loss of astrocytic processes in acute hippocampal slices prepared from glial fibrillary acidic protein-green fluorescent protein reporter mice. A sharp decrease in the number of mitochondria was also noted in acute slices, concurrently with an increase in mitochondrial size. Glycogen content decreased 3-fold upon slice preparation and did not recover despite stable recordings of field excitatory postsynaptic current. Analysis of Ca(2+) signaling showed that astrocytic responses to purine receptor and mGluR5 agonists differed in slice versus in vivo. These observations suggest that the functional properties and the fine structure of astrocytes in slices may be reflective of early stages of reactive gliosis and should be confirmed in vivo when possible. PMID:24272704

  3. SCRAPPER regulates the thresholds of long-term potentiation/depression, the bidirectional synaptic plasticity in hippocampal CA3-CA1 synapses.

    PubMed

    Takagi, Hiroshi; Setou, Mitsutoshi; Ito, Seiji; Yao, Ikuko

    2012-01-01

    SCRAPPER, which is an F-box protein encoded by FBXL20, regulates the frequency of the miniature excitatory synaptic current through the ubiquitination of Rab3-interacting molecule 1. Here, we recorded the induction of long-term potentiation/depression (LTP/LTD) in CA3-CA1 synapses in E3 ubiquitin ligase SCRAPPER-deficient hippocampal slices. Compared to wild-type mice, Scrapper-knockout mice exhibited LTDs with smaller magnitudes after induction with low-frequency stimulation and LTPs with larger magnitudes after induction with tetanus stimulation. These findings suggest that SCRAPPER regulates the threshold of bidirectional synaptic plasticity and, therefore, metaplasticity. PMID:23316391

  4. Enhancement of CA3 hippocampal network activity by activation of group II metabotropic glutamate receptors

    PubMed Central

    Ster, Jeanne; Mateos, José María; Grewe, Benjamin Friedrich; Coiret, Guyllaume; Corti, Corrado; Corsi, Mauro; Helmchen, Fritjof; Gerber, Urs

    2011-01-01

    Impaired function or expression of group II metabotropic glutamate receptors (mGluRIIs) is observed in brain disorders such as schizophrenia. This class of receptor is thought to modulate activity of neuronal circuits primarily by inhibiting neurotransmitter release. Here, we characterize a postsynaptic excitatory response mediated by somato-dendritic mGluRIIs in hippocampal CA3 pyramidal cells and in stratum oriens interneurons. The specific mGluRII agonists DCG-IV or LCCG-1 induced an inward current blocked by the mGluRII antagonist LY341495. Experiments with transgenic mice revealed a significant reduction of the inward current in mGluR3−/− but not in mGluR2−/− mice. The excitatory response was associated with periods of synchronized activity at theta frequency. Furthermore, cholinergically induced network oscillations exhibited decreased frequency when mGluRIIs were blocked. Thus, our data indicate that hippocampal responses are modulated not only by presynaptic mGluRIIs that reduce glutamate release but also by postsynaptic mGluRIIs that depolarize neurons and enhance CA3 network activity. PMID:21628565

  5. The Characteristics of LTP Induced in Hippocampal Slices Are Dependent on Slice-Recovery Conditions

    ERIC Educational Resources Information Center

    Godaux, Emile; Ris, Laurence; Capron, Brigitte; Sindic, Christian

    2006-01-01

    In area CA1 of hippocampal slices which are allowed to recover from slicing "in interface" and where recordings are carried out in interface, a single 1-sec train of 100-Hz stimulation triggers a short-lasting long-term potentiation (S-LTP), which lasts 1-2 h, whereas multiple 1-sec trains induce a long-lasting LTP (L-LTP), which lasts several…

  6. Axonal Morphometry of Hippocampal Pyramidal Neurons Semi-Automatically Reconstructed After In-Vivo Labeling in Different CA3 Locations

    PubMed Central

    Ropireddy, Deepak; Scorcioni, Ruggero; Lasher, Bonnie; Buzsáki, Gyorgy; Ascoli, Giorgio A.

    2013-01-01

    Axonal arbors of principal neurons form the backbone of neuronal networks in the mammalian cortex. Three-dimensional reconstructions of complete axonal trees are invaluable for quantitative analysis and modeling. However, digital data are still sparse due to labor intensity of reconstructing these complex structures. We augmented conventional tracing techniques with computational approaches to reconstruct fully labeled axonal morphologies. We digitized the axons of three rat hippocampal pyramidal cells intracellularly filled in-vivo from different CA3 sub-regions: two from areas CA3b and CA3c, respectively, toward the septal pole, and one from the posterior/ventral area (CA3pv) near the temporal pole. The reconstruction system was validated by comparing the morphology of the CA3c neuron with that traced from the same cell by a different operator on a standard commercial setup. Morphometric analysis revealed substantial differences among neurons. Total length ranged from 200mm (CA3b) to 500mm (CA3c), and axonal branching complexity peaked between 1mm (CA3b and CA3pv) and 2mm (CA3c) of Euclidean distance from the soma. Length distribution was analyzed among sub-regions (CA3a,b,c and CA1a,b,c), cytoarchitectonic layers, and longitudinal extent within a three-dimensional template of the rat hippocampus. The CA3b axon extended thrice more collaterals within CA3 than into CA1. On the contrary, the CA3c projection was double into CA1 than within CA3. Moreover, the CA3b axon extension was equal between strata oriens and radiatum, while the CA3c axon displayed an oriens/radiatum ratio of 1:6. The axonal distribution of the CA3pv neuron was intermediate between those of the CA3b and CA3c neurons both relative to sub-regions and layers, with uniform collateral presence across CA3/CA1 and moderate preponderance of radiatum over oriens. In contrast with the dramatic sub-region and layer differences, the axon longitudinal spread around the soma was similar for the three neurons

  7. Reversible loss of dendritic spines and altered excitability after chronic epilepsy in hippocampal slice cultures.

    PubMed Central

    Müller, M; Gähwiler, B H; Rietschin, L; Thompson, S M

    1993-01-01

    The morphological and functional consequences of epileptic activity were investigated by applying the convulsants bicuculline and/or picrotoxin to mature rat hippocampal slice cultures. After 3 days, some cells in all hippocampal subfields showed signs of degeneration, including swollen somata, vacuolation, and dendritic deformities, whereas others displayed only a massive reduction in the number of their dendritic spines. Intracellular recordings from CA3 pyramidal cells revealed a decrease in the amplitude of evoked excitatory synaptic potentials. gamma-Aminobutyric acid-releasing interneurons and inhibitory synaptic potentials were unaffected. Seven days after withdrawal of convulsants, remaining cells possessed a normal number of dendritic spines, thus demonstrating a considerable capacity for recovery. The pathological changes induced by convulsants are similar to those found in the hippocampi of human epileptics, suggesting that they are a consequence, rather than a cause, of epilepsy. Images PMID:8093558

  8. Third Trimester Equivalent Alcohol Exposure Reduces Modulation of Glutamatergic Synaptic Transmission by 5-HT1A Receptors in the Rat Hippocampal CA3 Region

    PubMed Central

    Morton, Russell A.; Valenzuela, C. Fernando

    2016-01-01

    Fetal alcohol exposure has been associated with many neuropsychiatric disorders that have been linked to altered serotonin (5-hydroxytryptamine; 5-HT) signaling, including depression and anxiety. During the first 2 weeks of postnatal life in rodents (equivalent to the third trimester of human pregnancy) 5-HT neurons undergo significant functional maturation and their axons reach target regions in the forebrain (e.g., cortex and hippocampus). The objective of this study was to identify the effects of third trimester ethanol (EtOH) exposure on hippocampal 5-HT signaling. Using EtOH vapor inhalation chambers, we exposed rat pups to EtOH for 4 h/day from postnatal day (P) 2 to P12. The average serum EtOH concentration in the pups was 0.13 ± 0.04 g/dl (legal intoxication limit in humans = 0.08 g/dl). We used brain slices to assess the modulatory actions of 5-HT on field excitatory postsynaptic potentials in the hippocampal CA3 region at P13-P15. Application of the GABAA/glycine receptor antagonist, picrotoxin, caused broadening of field excitatory postsynaptic potentials (fEPSPs), an effect that was reversed by application of 5-HT in slices from air exposed rats. However, this effect of 5-HT was absent in EtOH exposed animals. In slices from naïve animals, application of a 5-HT1A receptor antagonist blocked the effect of 5-HT on the fEPSPs recorded in presence of picrotoxin, suggesting that third trimester ethanol exposure acts by inhibiting the function of these receptors. Studies indicate that 5-HT1A receptors play a critical role in the development of hippocampal circuits. Therefore, inhibition of these receptors by third trimester ethanol exposure could contribute to the pathophysiology of fetal alcohol spectrum disorders. PMID:27375424

  9. Third Trimester Equivalent Alcohol Exposure Reduces Modulation of Glutamatergic Synaptic Transmission by 5-HT1A Receptors in the Rat Hippocampal CA3 Region.

    PubMed

    Morton, Russell A; Valenzuela, C Fernando

    2016-01-01

    Fetal alcohol exposure has been associated with many neuropsychiatric disorders that have been linked to altered serotonin (5-hydroxytryptamine; 5-HT) signaling, including depression and anxiety. During the first 2 weeks of postnatal life in rodents (equivalent to the third trimester of human pregnancy) 5-HT neurons undergo significant functional maturation and their axons reach target regions in the forebrain (e.g., cortex and hippocampus). The objective of this study was to identify the effects of third trimester ethanol (EtOH) exposure on hippocampal 5-HT signaling. Using EtOH vapor inhalation chambers, we exposed rat pups to EtOH for 4 h/day from postnatal day (P) 2 to P12. The average serum EtOH concentration in the pups was 0.13 ± 0.04 g/dl (legal intoxication limit in humans = 0.08 g/dl). We used brain slices to assess the modulatory actions of 5-HT on field excitatory postsynaptic potentials in the hippocampal CA3 region at P13-P15. Application of the GABAA/glycine receptor antagonist, picrotoxin, caused broadening of field excitatory postsynaptic potentials (fEPSPs), an effect that was reversed by application of 5-HT in slices from air exposed rats. However, this effect of 5-HT was absent in EtOH exposed animals. In slices from naïve animals, application of a 5-HT1A receptor antagonist blocked the effect of 5-HT on the fEPSPs recorded in presence of picrotoxin, suggesting that third trimester ethanol exposure acts by inhibiting the function of these receptors. Studies indicate that 5-HT1A receptors play a critical role in the development of hippocampal circuits. Therefore, inhibition of these receptors by third trimester ethanol exposure could contribute to the pathophysiology of fetal alcohol spectrum disorders. PMID:27375424

  10. Measurement of Inositol Triphosphate Levels from Rat Hippocampal Slices

    PubMed Central

    Tabatadze, Nino; Woolley, Catherine

    2016-01-01

    Inositol triphosphate (IP3) is an important second messenger that participates in signal transduction pathways in diverse cell types including hippocampal neurons. Stimulation of phospholipase C in response to various stimuli (hormones, growth factors, neurotransmitters, neurotrophins, neuromodulators, odorants, light, etc) results in hydrolysis of phosphatidylinositol 4, 5-bisphosphate (PIP2), a phospholipid that is located in the plasma membrane, and leads to the production of IP3 and diacylglycerol. Binding of IP3 to the IP3 receptor (IP3R) induces Ca2+ release from intracellular stores and enables the initiation of intracellular Ca2+-dependent signaling. Here we describe a procedure for the measurement of cellular IP3 levels in tissue homogenates prepared from rat hippocampal slices.

  11. Impaired retention of spatial memory after transection of longitudinally oriented axons of hippocampal CA3 pyramidal cells

    NASA Astrophysics Data System (ADS)

    Steffenach, Hill-Aina; Sloviter, Robert S.; Moser, Edvard I.; Moser, May-Britt

    2002-03-01

    Longitudinally oriented axon collaterals of CA3 pyramidal cells may be critical for integrating distributed information in the hippocampus. To investigate the possible role of this pathway in the retention of spatial memory, we made a single transversely oriented cut through the dorsal CA3 region of each hippocampus. Although the lesion involved <3% of the hippocampal volume, it nonetheless disrupted memory retention in a water maze in preoperatively trained rats. New learning in a different water maze was attenuated. No significant impairment occurred in rats with longitudinally oriented cuts, or in animals with ibotenic acid-induced lesions of similar magnitude. To characterize the effect of a focal lesion on the integrity of longitudinally projecting axons, we stained degenerating cells and fibers in rats with unilateral CA3 transections by using FluoroJade-B. Degenerating terminals were seen across a wide region posterior to the cut, and were present in the strata of areas CA3 and CA1 that are innervated by CA3 pyramidal cells. These results suggest that the integrity of longitudinally oriented, translamellar axons of CA3 pyramidal cells may be necessary for efficient acquisition and retention of spatial memory.

  12. Impaired retention of spatial memory after transection of longitudinally oriented axons of hippocampal CA3 pyramidal cells

    PubMed Central

    Steffenach, Hill-Aina; Sloviter, Robert S.; Moser, Edvard I.; Moser, May-Britt

    2002-01-01

    Longitudinally oriented axon collaterals of CA3 pyramidal cells may be critical for integrating distributed information in the hippocampus. To investigate the possible role of this pathway in the retention of spatial memory, we made a single transversely oriented cut through the dorsal CA3 region of each hippocampus. Although the lesion involved <3% of the hippocampal volume, it nonetheless disrupted memory retention in a water maze in preoperatively trained rats. New learning in a different water maze was attenuated. No significant impairment occurred in rats with longitudinally oriented cuts, or in animals with ibotenic acid-induced lesions of similar magnitude. To characterize the effect of a focal lesion on the integrity of longitudinally projecting axons, we stained degenerating cells and fibers in rats with unilateral CA3 transections by using FluoroJade-B. Degenerating terminals were seen across a wide region posterior to the cut, and were present in the strata of areas CA3 and CA1 that are innervated by CA3 pyramidal cells. These results suggest that the integrity of longitudinally oriented, translamellar axons of CA3 pyramidal cells may be necessary for efficient acquisition and retention of spatial memory. PMID:11867718

  13. Atorvastatin enhances kainate-induced gamma oscillations in rat hippocampal slices.

    PubMed

    Li, Chengzhang; Wang, Jiangang; Zhao, Jianhua; Wang, Yali; Liu, Zhihua; Guo, Fang Li; Wang, Xiao Fang; Vreugdenhil, Martin; Lu, Cheng Biao

    2016-09-01

    Atorvastatin has been shown to affect cognitive functions in rodents and humans. However, the underlying mechanism is not fully understood. Because hippocampal gamma oscillations (γ, 20-80 Hz) are associated with cognitive functions, we studied the effect of atorvastatin on persistent kainate-induced γ oscillation in the CA3 area of rat hippocampal slices. The involvement of NMDA receptors and multiple kinases was tested before and after administration of atorvastatin. Whole-cell current-clamp and voltage-clamp recordings were made from CA3 pyramidal neurons and interneurons before and after atorvastatin application. Atorvastatin increased γ power by ~ 50% in a concentration-dependent manner, without affecting dominant frequency. Whereas atorvastatin did not affect intrinsic properties of both pyramidal neurons and interneurons, it increased the firing frequency of interneurons but not that of pyramidal neurons. Furthermore, whereas atorvastatin did not affect synaptic current amplitude, it increased the frequency of spontaneous inhibitory post-synaptic currents, but did not affect the frequency of spontaneous excitatory post-synaptic currents. The atorvastatin-induced enhancement of γ oscillations was prevented by pretreatment with the PKA inhibitor H89, the ERK inhibitor U0126, or the PI3K inhibitor wortmanin, but not by the NMDA receptor antagonist D-AP5. Taken together, these results demonstrate that atorvastatin enhanced the kainate-induced γ oscillation by increasing interneuron excitability, with an involvement of multiple intracellular kinase pathways. Our study suggests that the classical cholesterol-lowering agent atorvastatin may improve cognitive functions compromised in disease, via the enhancement of hippocampal γ oscillations. PMID:27336700

  14. Cellular mechanisms of 4-aminopyridine-induced synchronized after-discharges in the rat hippocampal slice.

    PubMed Central

    Traub, R D; Colling, S B; Jefferys, J G

    1995-01-01

    1. We constructed a model of the in vitro rodent CA3 region with 128 pyramidal neurones and twenty-four inhibitory neurones. The model was used to analyse synchronized firing induced in the rat hippocampal slice by 4-aminopyridine (4-AP), a problem simultaneously studied in experiments in rat hippocampal slices. N-methyl-D-aspartate (NMDA) receptors were blocked. 2. Consistent with a known action of 4-AP, unitary EPSCs were assumed to be large and prolonged. With augmented EPSCs, spontaneous synchronized bursts occurred in the model if random ectopic axonal spikes were present. We observed probable antidromic spikes and miniature spikes experimentally. 3. Consistent with experiment, model synchronized bursts were preceded by a period of about 100 ms of increased unit activity and cell depolarization. In the model, this was caused in part by EPSPs consequent to ectopic axonal spikes. 4. After widespread firing had begun, full-blown synchrony in the model required orthodromic EPSPs. A single synchronized burst, once initiated, could proceed without further ectopic activity. 5. A depolarizing change in reversal potential for dendritic GABAA favoured the occurrence of synchronized after-discharges in the model. Consistent with this, bicuculline was found to block after-discharges in slices bathed in 4-AP (70 microM) during NMDA blockade. 6. These data indicate that, even with synaptic inhibition present, ectopic spikes can 'set the stage' for synchronized activity by depolarizing pyramidal cell dendrites, but that recurrent orthodromic EPSPs are required for expression of this synchrony. When synaptic inhibition is present, EPSCs may need to be larger than usual for synchrony to take place. Secondary bursts in 4-AP appear to be driven in part by a depolarizing GABAA-mediated current. PMID:8583397

  15. Persistent Gliosis Interferes with Neurogenesis in Organotypic Hippocampal Slice Cultures

    PubMed Central

    Gerlach, Johannes; Donkels, Catharina; Münzner, Gert; Haas, Carola A.

    2016-01-01

    Neurogenesis in the adult hippocampus has become an intensively investigated research topic, as it is essential for proper hippocampal function and considered to bear therapeutic potential for the replacement of pathologically lost neurons. On the other hand, neurogenesis itself is frequently affected by CNS insults. To identify processes leading to the disturbance of neurogenesis, we made use of organotypic hippocampal slice cultures (OHSC), which, for unknown reasons, lose their neurogenic potential during cultivation. In the present study, we show by BrdU/Prox1 double-immunostaining that the generation of new granule cells drops by 90% during the first week of cultivation. Monitoring neurogenesis dynamically in OHSC from POMC-eGFP mice, in which immature granule cells are endogenously labeled, revealed a gradual decay of the eGFP signal, reaching 10% of initial values within 7 days of cultivation. Accordingly, reverse transcription quantitative polymerase chain reaction analysis showed the downregulation of the neurogenesis-related genes doublecortin and Hes5, a crucial target of the stem cell-maintaining Notch signaling pathway. In parallel, we demonstrate a strong and long-lasting activation of astrocytes and microglial cells, both, morphologically and on the level of gene expression. Enhancement of astroglial activation by treating OHSC with ciliary neurotrophic factor accelerated the loss of neurogenesis, whereas treatment with indomethacin or an antagonist of the purinergic P2Y12 receptor exhibited potent protective effects on the neurogenic outcome. Therefore, we conclude that OHSC rapidly lose their neurogenic capacity due to persistent inflammatory processes taking place after the slice preparation. As inflammation is also considered to affect neurogenesis in many CNS pathologies, OHSC appear as a useful tool to study this interplay and its molecular basis. Furthermore, we propose that modification of glial activation might bear the therapeutic potential

  16. Persistent Gliosis Interferes with Neurogenesis in Organotypic Hippocampal Slice Cultures.

    PubMed

    Gerlach, Johannes; Donkels, Catharina; Münzner, Gert; Haas, Carola A

    2016-01-01

    Neurogenesis in the adult hippocampus has become an intensively investigated research topic, as it is essential for proper hippocampal function and considered to bear therapeutic potential for the replacement of pathologically lost neurons. On the other hand, neurogenesis itself is frequently affected by CNS insults. To identify processes leading to the disturbance of neurogenesis, we made use of organotypic hippocampal slice cultures (OHSC), which, for unknown reasons, lose their neurogenic potential during cultivation. In the present study, we show by BrdU/Prox1 double-immunostaining that the generation of new granule cells drops by 90% during the first week of cultivation. Monitoring neurogenesis dynamically in OHSC from POMC-eGFP mice, in which immature granule cells are endogenously labeled, revealed a gradual decay of the eGFP signal, reaching 10% of initial values within 7 days of cultivation. Accordingly, reverse transcription quantitative polymerase chain reaction analysis showed the downregulation of the neurogenesis-related genes doublecortin and Hes5, a crucial target of the stem cell-maintaining Notch signaling pathway. In parallel, we demonstrate a strong and long-lasting activation of astrocytes and microglial cells, both, morphologically and on the level of gene expression. Enhancement of astroglial activation by treating OHSC with ciliary neurotrophic factor accelerated the loss of neurogenesis, whereas treatment with indomethacin or an antagonist of the purinergic P2Y12 receptor exhibited potent protective effects on the neurogenic outcome. Therefore, we conclude that OHSC rapidly lose their neurogenic capacity due to persistent inflammatory processes taking place after the slice preparation. As inflammation is also considered to affect neurogenesis in many CNS pathologies, OHSC appear as a useful tool to study this interplay and its molecular basis. Furthermore, we propose that modification of glial activation might bear the therapeutic potential

  17. CA3 Synaptic Silencing Attenuates Kainic Acid-Induced Seizures and Hippocampal Network Oscillations123

    PubMed Central

    Yu, Lily M. Y.; Wintzer, Marie E.

    2016-01-01

    Abstract Epilepsy is a neurological disorder defined by the presence of seizure activity, manifest both behaviorally and as abnormal activity in neuronal networks. An established model to study the disorder in rodents is the systemic injection of kainic acid, an excitatory neurotoxin that at low doses quickly induces behavioral and electrophysiological seizures. Although the CA3 region of the hippocampus has been suggested to be crucial for kainic acid-induced seizure, because of its strong expression of kainate glutamate receptors and its high degree of recurrent connectivity, the precise role of excitatory transmission in CA3 in the generation of seizure and the accompanying increase in neuronal oscillations remains largely untested. Here we use transgenic mice in which CA3 pyramidal cell synaptic transmission can be inducibly silenced in the adult to demonstrate CA3 excitatory output is required for both the generation of epileptiform oscillatory activity and the progression of behavioral seizures. PMID:27022627

  18. Live imaging of microtubule dynamics in organotypic hippocampal slice cultures.

    PubMed

    Schätzle, Philipp; Kapitein, Lukas C; Hoogenraad, Casper C

    2016-01-01

    The microtubule (MT) cytoskeleton plays an active role during different phases of neuronal development and is an essential structure for stable neuronal morphology. MTs determine axon formation, control polarized cargo trafficking, and regulate the dynamics of dendritic spines, the major sites of excitatory synaptic input. Defects in MT function have been linked to various neurological and neurodegenerative diseases and recent studies highlight neuronal MTs as a potential target for therapeutic intervention. Thus, understanding MT dynamics and its regulation is of central importance to study many aspects of neuronal function. The dynamics of MT in neurons can be studied by visualizing fluorescently tagged MT plus-end tracking proteins (+TIPs). Tracking of +TIP trajectories allows analyzing the speeds and directionality of MT growth in axons and dendrites. Numerous labs now use +TIP to track growing MTs in dissociated neuron cultures. This chapter provides detailed methods for live imaging of MT dynamics in organotypic hippocampal slice cultures. We describe protocols for culturing and transducing organotypic slices and imaging MT dynamics by spinning disk confocal microscopy. PMID:26794510

  19. Enhancement of Hippocampal CA3 Neuronal Dendritic Arborization by Glycyrrhiza glabra root extract Treatment in Wistar Albino Rats

    PubMed Central

    Chakravarthi, Kosuri Kalyan; Avadhani, Ramakrishna

    2014-01-01

    Background: In the traditional system of medicine, the roots and rhizomes of Glycyrrhiza glabra (Gg) (family: Leguminosae) have been in clinical use for centuries. Aim: In the present study, we investigated the role of aqueous extract of root of Gg treatment on the dendritic morphology of hippocampal Cornu Ammonis area three (CA3) neurons, one of the regions concerned with learning and memory, in 1- month- old male Wistar albino rats. Materials and Methods: The aqueous extract of root of Gg was administered orally in four doses (75, 150, 225 and 300 mg/kg) for 4 weeks. After the treatment period, all experimental animals were subjected to spatial learning (Morris water maze, Hebb-William's maze and elevated plus maze) tests. At the end of the spatial memory tests, the rats were deeply anesthetized with Pentobarbitone and killed their brains were removed rapidly and fixed in rapid Golgi fixative. Hippocampal CA3 neurons were traced using camera lucida, and dendritic arborization and intersections were quantified. These data were compared to those of age-matched control rats. Results: The aqueous root extract of Gg in the dose of 150 and 225 mg/kg/p.o showed a significant (P < 0.01) enhancement of dendritic arborization (dendritic branching points) and dendritic intersections along the length of both apical and basal dendrites in hippocampal (CA3) pyramidal neurons is comparable to control. Conclusion: Based on our results obtained, we conclude that constituents present in aqueous root extract of Gg have neuronal dendritic growth stimulating properties. PMID:24678192

  20. Cascade of tau toxicity in inducible hippocampal brain slices and prevention by aggregation inhibitors

    PubMed Central

    Messing, Lars; Mandelkow, Eckhard; Mandelkow, Eva-Maria

    2016-01-01

    Mislocalization and aggregation of the axonal protein Tau are hallmarks of Alzheimer disease and other tauopathies. Here, we studied the relationship between Tau aggregation, loss of spines and neurons, and reversibility by aggregation inhibitors. To this end we established an in vitro model of tauopathy based on regulatable transgenic hippocampal organotypic slice cultures prepared from mice expressing pro-aggregant TauRDΔK. Transgene expression was monitored by a bioluminescence reporter assay. Abnormal Tau phosphorylation, mislocalization of exogenous and endogenous Tau into the somatodendritic compartment, followed by reduction of dendritic spines, altered morphology from mushroom-shaped to thin spines, dysregulation of Ca++ dynamics, Tau aggregation, neuronal loss and elevated activation of microglia. Neurotoxicity was mediated by Caspase-3 activation and correlated with the expression level of pro-aggregant TauRDΔK. Finally, Tau aggregates appeared in areas CA1 and CA3 after three weeks in vitro. Neurodegeneration was relieved by aggregation inhibitors or by switching off transgene expression. Thus the slice culture model is suitable for monitoring the development of tauopathy and the therapeutic benefit of anti-aggregation drugs. PMID:23158765

  1. CREB Antisense Oligodeoxynucleotide Administration into the Dorsal Hippocampal CA3 Region Impairs Long- but Not Short-Term Spatial Memory in Mice

    ERIC Educational Resources Information Center

    Florian, Cedrick; Mons, Nicole; Roullet, Pascal

    2006-01-01

    The transcription factor cAMP response-element binding protein (CREB) has a pivotal role in hippocampal synaptic plasticity and hippocampus-dependent long-term memory. We recently demonstrated that the dorsal hippocampal CA3 region is involved in memory consolidation of spatial information tested on a Morris water maze in mice. To test whether…

  2. Temperature effects on evoked potentials of hippocampal slices from euthermic chipmunks, hamsters and rats

    NASA Technical Reports Server (NTRS)

    Hooper, D. C.; Martin, S. M.; Horowitz, J. M.

    1985-01-01

    1. Neural activity was recorded in hippocampal slices from euthermic chipmunks, hamsters and rats. 2. While recording the evoked potentials, the temperature of the Ringer's solution bathing the slice was varied by controlling the temperature of an outer chamber jacketing the recording chamber. 3. The temperature just below that at which a population spike could be evoked, Tt, was 10.4 +/- 0.3 degrees C (mean +/- SEM) for chipmunk slices, 14.1 +/- 0.4 degrees C for rat slices and 14.8 +/- 0.4 degrees C for hamster slices. Tt was significantly lower in the chipmunk slices (P<0.01) than in the rat and hamster slices. 4. Data were interpreted as consistent with the hypothesis that chipmunk hippocampal neurons are intrinsically cold resistant.

  3. Microglial polarization and plasticity: evidence from organotypic hippocampal slice cultures.

    PubMed

    Ajmone-Cat, Maria Antonietta; Mancini, Melissa; De Simone, Roberta; Cilli, Piera; Minghetti, Luisa

    2013-10-01

    Increasing evidence indicates that "functional plasticity" is not solely a neuronal attribute but a hallmark of microglial cells, the main brain resident macrophage population. Far from being a univocal phenomenon, microglial activation can originate a plethora of functional phenotypes, encompassing the classic M1 proinflammatory and the alternative M2 anti-inflammatory phenotypes. This concept overturns the popular view of microglial activation as a synonym of neurotoxicity and neurogenesis failure in brain disorders. The characterization of the alternative programs is a matter of intense investigation, but still scarce information is available on the course of microglial activation, on the reversibility of the different commitments and on the capability of preserving molecular memory of previous priming stimuli. By using organotypic hippocampal slice cultures as a model, we developed paradigms of stimulation aimed at shedding light on some of these aspects. We show that persistent stimulation of TLR4 signaling promotes an anti-inflammatory response and microglial polarization toward M2-like phenotype. Moreover, acute and chronic preconditioning regimens permanently affect the capability to respond to a later challenge, suggesting the onset of mechanisms of molecular memory. Similar phenomena could occur in the intact brain and differently affect the vulnerability of mature and newborn neurons to noxious signals. PMID:23918452

  4. Hippocampal CA3 Transcriptome Signature Correlates with Initial Precipitating Injury in Refractory Mesial Temporal Lobe Epilepsy

    PubMed Central

    Bando, Silvia Y.; Alegro, Maryana C.; Amaro, Edson; Silva, Alexandre V.; Castro, Luiz H. M.; Wen, Hung-Tzu; Lima, Leandro de A.; Brentani, Helena; Moreira-Filho, Carlos Alberto

    2011-01-01

    Background Prolonged febrile seizures constitute an initial precipitating injury (IPI) commonly associated with refractory mesial temporal lobe epilepsy (RMTLE). In order to investigate IPI influence on the transcriptional phenotype underlying RMTLE we comparatively analyzed the transcriptomic signatures of CA3 explants surgically obtained from RMTLE patients with (FS) or without (NFS) febrile seizure history. Texture analyses on MRI images of dentate gyrus were conducted in a subset of surgically removed sclerotic hippocampi for identifying IPI-associated histo-radiological alterations. Methodology/Principal Findings DNA microarray analysis revealed that CA3 global gene expression differed significantly between FS and NFS subgroups. An integrative functional genomics methodology was used for characterizing the relations between GO biological processes themes and constructing transcriptional interaction networks defining the FS and NFS transcriptomic signatures and its major gene-gene links (hubs). Co-expression network analysis showed that: i) CA3 transcriptomic profiles differ according to the IPI; ii) FS distinctive hubs are mostly linked to glutamatergic signalization while NFS hubs predominantly involve GABAergic pathways and neurotransmission modulation. Both networks have relevant hubs related to nervous system development, what is consistent with cell genesis activity in the hippocampus of RMTLE patients. Moreover, two candidate genes for therapeutic targeting came out from this analysis: SSTR1, a relevant common hub in febrile and afebrile transcriptomes, and CHRM3, due to its putative role in epilepsy susceptibility development. MRI texture analysis allowed an overall accuracy of 90% for pixels correctly classified as belonging to FS or NFS groups. Histological examination revealed that granule cell loss was significantly higher in FS hippocampi. Conclusions/Significance CA3 transcriptional signatures and dentate gyrus morphology fairly correlate with IPI

  5. Suppression of adult neurogenesis impairs population coding of similar contexts in hippocampal CA3 region

    PubMed Central

    Niibori, Yosuke; Yu, Tzong-Shiue; Epp, Jonathan R.; Akers, Katherine G.; Josselyn, Sheena A.; Frankland, Paul W.

    2016-01-01

    Different places may share common features, but are coded by distinct populations of CA3 neurons in the hippocampus. Here we show that chemical or genetic suppression of adult neurogenesis in the hippocampus impairs this population-based coding of similar (but not dissimilar) contexts. These data provide a neural basis for impaired spatial discrimination following ablation of adult neurogenesis, and support the proposal that adult neurogenesis regulates the efficiency of a pattern separation process in the hippocampus. PMID:23212382

  6. Early adenosine release contributes to hypoxia-induced disruption of stimulus-induced sharp wave-ripple complexes in rat hippocampal area CA3.

    PubMed

    Jarosch, Marlene S; Gebhardt, Christine; Fano, Silvia; Huchzermeyer, Christine; Ul Haq, Rizwan; Behrens, Christoph J; Heinemann, Uwe

    2015-07-01

    We investigated the effects of hypoxia on sharp wave-ripple complex (SPW-R) activity and recurrent epileptiform discharges in rat hippocampal slices, and the mechanisms underlying block of this activity. Oxygen levels were measured using Clark-style oxygen sensor microelectrodes. In contrast to recurrent epileptiform discharges, oxygen consumption was negligible during SPW-R activity. These network activities were reversibly blocked when oxygen levels were reduced to 20% or less for 3 min. The prolongation of hypoxic periods to 6 min caused reversible block of SPW-Rs during 20% oxygen and irreversible block when 0% oxygen (anoxia) was applied. In contrast, recurrent epileptiform discharges were more resistant to prolonged anoxia and almost fully recovered after 6 min of anoxia. SPW-Rs were unaffected by the application of 1-butyl-3-(4-methylphenylsulfonyl) urea, a blocker of KATP channels, but they were blocked by activation of adenosine A1 receptors. In support of a modulatory function of adenosine, the amplitude and incidence of SPW-Rs were increased during application of the A1 receptor antagonist 8-cyclopentyl-1,3-dipropylxanthine (DPCPX). Interestingly, hypoxia decreased the frequency of miniature excitatory post-synaptic currents in CA3 pyramidal cells, an effect that was converted into increased frequency by the adenosine A1 agonist DPCPX. In addition, DPCPX also delayed the onset of hypoxia-mediated block of SPW-Rs. Our data suggest that early adenosine release during hypoxia induces a decrease in pre-synaptic glutamate release and that both might contribute to transient block of SPW-Rs during hypoxia/anoxia in area CA3. PMID:25959377

  7. Long-term potentiation in the hippocampal slice: evidence for stimulated secretion of newly synthesized proteins

    SciTech Connect

    Duffy, C.; Teyler, T.J.; Shashoua, V.E.

    1981-06-01

    Long-term potentiation of the hippocampal slice preparation results in an increase in the incorporation of labeled valine into the proteins destined for secretion into the extracellular medium. Double-labeling methods established that the increased secretion of the labeled proteins was limited to the potentiated region of a slice; incorporation of labeled valine was increased in the hippocampus if potentiation was through the Schaffer collaterals and in the dentate if potentiation was through the perforant path. Controls for nonspecific stimulation showed no changes. There appears to be a link between long-term potentiation and the metabolic processes that lead to protein synthesis in the hippocampal slice system.

  8. Dopamine D3 Receptors Inhibit Hippocampal Gamma Oscillations by Disturbing CA3 Pyramidal Cell Firing Synchrony.

    PubMed

    Lemercier, Clément E; Schulz, Steffen B; Heidmann, Karin E; Kovács, Richard; Gerevich, Zoltan

    2015-01-01

    Cortical gamma oscillations are associated with cognitive processes and are altered in several neuropsychiatric conditions such as schizophrenia and Alzheimer's disease. Since dopamine D3 receptors are possible targets in treatment of these conditions, it is of great importance to understand their role in modulation of gamma oscillations. The effect of D3 receptors on gamma oscillations and the underlying cellular mechanisms were investigated by extracellular local field potential and simultaneous intracellular sharp micro-electrode recordings in the CA3 region of the hippocampus in vitro. D3 receptors decreased the power and broadened the bandwidth of gamma oscillations induced by acetylcholine or kainate. Blockade of the D3 receptors resulted in faster synchronization of the oscillations, suggesting that endogenous dopamine in the hippocampus slows down the dynamics of gamma oscillations by activation of D3 receptors. Investigating the underlying cellular mechanisms for these effects showed that D3 receptor activation decreased the rate of action potentials (APs) during gamma oscillations and reduced the precision of the AP phase coupling to the gamma cycle in CA3 pyramidal cells. The results may offer an explanation how selective activation of D3 receptors may impair cognition and how, in converse, D3 antagonists may exert pro-cognitive and antipsychotic effects. PMID:26779018

  9. Dopamine D3 Receptors Inhibit Hippocampal Gamma Oscillations by Disturbing CA3 Pyramidal Cell Firing Synchrony

    PubMed Central

    Lemercier, Clément E.; Schulz, Steffen B.; Heidmann, Karin E.; Kovács, Richard; Gerevich, Zoltan

    2016-01-01

    Cortical gamma oscillations are associated with cognitive processes and are altered in several neuropsychiatric conditions such as schizophrenia and Alzheimer’s disease. Since dopamine D3 receptors are possible targets in treatment of these conditions, it is of great importance to understand their role in modulation of gamma oscillations. The effect of D3 receptors on gamma oscillations and the underlying cellular mechanisms were investigated by extracellular local field potential and simultaneous intracellular sharp micro-electrode recordings in the CA3 region of the hippocampus in vitro. D3 receptors decreased the power and broadened the bandwidth of gamma oscillations induced by acetylcholine or kainate. Blockade of the D3 receptors resulted in faster synchronization of the oscillations, suggesting that endogenous dopamine in the hippocampus slows down the dynamics of gamma oscillations by activation of D3 receptors. Investigating the underlying cellular mechanisms for these effects showed that D3 receptor activation decreased the rate of action potentials (APs) during gamma oscillations and reduced the precision of the AP phase coupling to the gamma cycle in CA3 pyramidal cells. The results may offer an explanation how selective activation of D3 receptors may impair cognition and how, in converse, D3 antagonists may exert pro-cognitive and antipsychotic effects. PMID:26779018

  10. Holographic Photolysis for Multiple Cell Stimulation in Mouse Hippocampal Slices

    PubMed Central

    Papagiakoumou, Eirini; Ventalon, Cathie; Angulo, María Cecilia; Emiliani, Valentina

    2010-01-01

    Background Advanced light microscopy offers sensitive and non-invasive means to image neural activity and to control signaling with photolysable molecules and, recently, light-gated channels. These approaches require precise and yet flexible light excitation patterns. For synchronous stimulation of subsets of cells, they also require large excitation areas with millisecond and micrometric resolution. We have recently developed a new method for such optical control using a phase holographic modulation of optical wave-fronts, which minimizes power loss, enables rapid switching between excitation patterns, and allows a true 3D sculpting of the excitation volumes. In previous studies we have used holographic photololysis to control glutamate uncaging on single neuronal cells. Here, we extend the use of holographic photolysis for the excitation of multiple neurons and of glial cells. Methods/Principal Findings The system combines a liquid crystal device for holographic patterned photostimulation, high-resolution optical imaging, the HiLo microscopy, to define the stimulated regions and a conventional Ca2+ imaging system to detect neural activity. By means of electrophysiological recordings and calcium imaging in acute hippocampal slices, we show that the use of excitation patterns precisely tailored to the shape of multiple neuronal somata represents a very efficient way for the simultaneous excitation of a group of neurons. In addition, we demonstrate that fast shaped illumination patterns also induce reliable responses in single glial cells. Conclusions/Significance We show that the main advantage of holographic illumination is that it allows for an efficient excitation of multiple cells with a spatiotemporal resolution unachievable with other existing approaches. Although this paper focuses on the photoactivation of caged molecules, our approach will surely prove very efficient for other probes, such as light-gated channels, genetically encoded photoactivatable

  11. Tonic GABAA conductance bidirectionally controls interneuron firing pattern and synchronization in the CA3 hippocampal network

    PubMed Central

    Pavlov, Ivan; Savtchenko, Leonid P.; Song, Inseon; Koo, Jaeyeon; Pimashkin, Alexey; Rusakov, Dmitri A.; Semyanov, Alexey

    2014-01-01

    The spiking output of interneurons is key for rhythm generation in the brain. However, what controls interneuronal firing remains incompletely understood. Here we combine dynamic clamp experiments with neural network simulations to understand how tonic GABAA conductance regulates the firing pattern of CA3 interneurons. In baseline conditions, tonic GABAA depolarizes these cells, thus exerting an excitatory action while also reducing the excitatory postsynaptic potential (EPSP) amplitude through shunting. As a result, the emergence of weak tonic GABAA conductance transforms the interneuron firing pattern driven by individual EPSPs into a more regular spiking mode determined by the cell intrinsic properties. The increased regularity of spiking parallels stronger synchronization of the local network. With further increases in tonic GABAA conductance the shunting inhibition starts to dominate over excitatory actions and thus moderates interneuronal firing. The remaining spikes tend to follow the timing of suprathreshold EPSPs and thus become less regular again. The latter parallels a weakening in network synchronization. Thus, our observations suggest that tonic GABAA conductance can bidirectionally control brain rhythms through changes in the excitability of interneurons and in the temporal structure of their firing patterns. PMID:24344272

  12. Pharmacological Intervention of Hippocampal CA3 NMDA Receptors Impairs Acquisition and Long-Term Memory Retrieval of Spatial Pattern Completion Task

    ERIC Educational Resources Information Center

    Fellini, Laetitia; Florian, Cedrick; Courtey, Julie; Roullet, Pascal

    2009-01-01

    Pattern completion is the ability to retrieve complete information on the basis of incomplete retrieval cues. Although it has been demonstrated that this cognitive capacity depends on the NMDA receptors (NMDA-Rs) of the hippocampal CA3 region, the role played by these glutamatergic receptors in the pattern completion process has not yet been…

  13. Carbachol-induced rhythmic slow activity (theta) in cat hippocampal formation slices.

    PubMed

    Konopacki, J; Gołebiewski, H; Eckersdorf, B

    1992-04-24

    Application of the cholinergic agonist, carbachol, produced theta-like rhythmical waveforms, recorded in the stratum moleculare of the dentate gyrus in the cat hippocampal formation slices. This effect of carbachol was antagonized by atropine but not D-tubocurarine. These results provide first direct evidence that the hippocampal formation neuronal network in the cat is capable of producing synchronized slow wave activity when isolated from pulsed rhythmic inputs of the medial septum. PMID:1511270

  14. HERC 1 Ubiquitin Ligase Mutation Affects Neocortical, CA3 Hippocampal and Spinal Cord Projection Neurons: An Ultrastructural Study

    PubMed Central

    Ruiz, Rocío; Pérez-Villegas, Eva María; Bachiller, Sara; Rosa, José Luis; Armengol, José Angel

    2016-01-01

    The spontaneous mutation tambaleante is caused by the Gly483Glu substitution in the highly conserved N terminal RCC1-like domain of the HERC1 protein, which leads to the increase of mutated protein levels responsible for cerebellar Purkinje cell death by autophagy. Until now, Purkinje cells have been the only central nervous neurons reported as being targeted by the mutation, and their degeneration elicits an ataxic syndrome in adult mutant mice. However, the ultrastructural analysis performed here demonstrates that signs of autophagy, such as autophagosomes, lysosomes, and altered mitochondria, are present in neocortical pyramidal, CA3 hippocampal pyramidal, and spinal cord motor neurons. The main difference is that the reduction in the number of neurons affected in the tambaleante mutation in the neocortex, the hippocampus, and the spinal cord is not so evident as the dramatic loss of cerebellar Purkinje cells. Interestingly, signs of autophagy are absent in both interneurons and neuroglia cells. Affected neurons have in common that they are projection neurons which receive strong and varied synaptic inputs, and possess the highest degree of neuronal activity. Therefore, because the integrity of the ubiquitin-proteasome system is essential for protein degradation and hence, for normal protein turnover, it could be hypothesized that the deleterious effects of the misrouting of these pathways would depend directly on the neuronal activity. PMID:27147983

  15. HERC 1 Ubiquitin Ligase Mutation Affects Neocortical, CA3 Hippocampal and Spinal Cord Projection Neurons: An Ultrastructural Study.

    PubMed

    Ruiz, Rocío; Pérez-Villegas, Eva María; Bachiller, Sara; Rosa, José Luis; Armengol, José Angel

    2016-01-01

    The spontaneous mutation tambaleante is caused by the Gly483Glu substitution in the highly conserved N terminal RCC1-like domain of the HERC1 protein, which leads to the increase of mutated protein levels responsible for cerebellar Purkinje cell death by autophagy. Until now, Purkinje cells have been the only central nervous neurons reported as being targeted by the mutation, and their degeneration elicits an ataxic syndrome in adult mutant mice. However, the ultrastructural analysis performed here demonstrates that signs of autophagy, such as autophagosomes, lysosomes, and altered mitochondria, are present in neocortical pyramidal, CA3 hippocampal pyramidal, and spinal cord motor neurons. The main difference is that the reduction in the number of neurons affected in the tambaleante mutation in the neocortex, the hippocampus, and the spinal cord is not so evident as the dramatic loss of cerebellar Purkinje cells. Interestingly, signs of autophagy are absent in both interneurons and neuroglia cells. Affected neurons have in common that they are projection neurons which receive strong and varied synaptic inputs, and possess the highest degree of neuronal activity. Therefore, because the integrity of the ubiquitin-proteasome system is essential for protein degradation and hence, for normal protein turnover, it could be hypothesized that the deleterious effects of the misrouting of these pathways would depend directly on the neuronal activity. PMID:27147983

  16. Interplay between synchronization of multivesicular release and recruitment of additional release sites support short-term facilitation at hippocampal mossy fiber to CA3 pyramidal cells synapses.

    PubMed

    Chamberland, Simon; Evstratova, Alesya; Tóth, Katalin

    2014-08-13

    Synaptic short-term plasticity is a key regulator of neuronal communication and is controlled via various mechanisms. A well established property of mossy fiber to CA3 pyramidal cell synapses is the extensive short-term facilitation during high-frequency bursts. We investigated the mechanisms governing facilitation using a combination of whole-cell electrophysiological recordings, electrical minimal stimulation, and random-access two-photon microscopy in acute mouse hippocampal slices. Two distinct presynaptic mechanisms were involved in short-term facilitation, with their relative contribution dependent on extracellular calcium concentration. The synchronization of multivesicular release was observed during trains of facilitating EPSCs recorded in 1.2 mM external Ca(2+) ([Ca(2+)]e). Indeed, covariance analysis revealed a gradual augmentation in quantal size during trains of EPSCs, and application of the low-affinity glutamate receptor antagonist γ-D-glutamylglycine showed an increase in cleft glutamate concentration during paired-pulse stimulation. Whereas synchronization of multivesicular release contributed to the facilitation in 1.2 mM [Ca(2+)]e, variance-mean analysis showed that recruitment of more release sites (N) was likely to account for the larger facilitation observed in 2.5 mM [Ca(2+)]e. Furthermore, this increase in N could be promoted by calcium microdomains of heterogeneous amplitudes observed in single mossy fiber boutons. Our findings suggest that the combination of multivesicular release and the recruitment of additional release sites act together to increase glutamate release during burst activity. This is supported by the compartmentalized spatial profile of calcium elevations in boutons and helps to expand the dynamic range of mossy fibers information transfer. PMID:25122902

  17. CREB antisense oligodeoxynucleotide administration into the dorsal hippocampal CA3 region impairs long- but not short-term spatial memory in mice

    PubMed Central

    Florian, Cédrick; Mons, Nicole; Roullet, Pascal

    2006-01-01

    The transcription factor cAMP response-element binding protein (CREB) has a pivotal role in hippocampal synaptic plasticity and hippocampus-dependent long-term memory. We recently demonstrated that the dorsal hippocampal CA3 region is involved in memory consolidation of spatial information tested on a Morris water maze in mice. To test whether activation of CREB in the CA3 region is required for memory consolidation of spatial information, bilaterally cannulated mice were infused 18 h before the beginning of the behavioral training with antisense or control sense CREB oligodeoxynucleotides (ODNs) or buffer. Mice were then subjected to massed training in a spatial version of the water maze and tested for retention 0 or 24 h after the last training session. We showed that CREB antisense ODN-infusion in the CA3 region impaired long-term memory when tested 24 h later but had no effect on spatial acquisition or short-term memory tested immediately after behavioral training. These findings provide evidence that the regionally restricted activation of CREB in the dorsal hippocampal CA3 region is critical for the long-term memory consolidation phase of spatial learning but not for short-term memory. PMID:16882863

  18. Preparation of postsynaptic density fraction from hippocampal slices and proteomic analysis

    SciTech Connect

    Dosemeci, Ayse . E-mail: dosemeca@mail.nih.gov; Tao-Cheng, J.-H.; Vinade, Lucia; Jaffe, Howard

    2006-01-13

    Hippocampal slices offer an excellent experimental system for the study of activity-induced changes in the postsynaptic density (PSD). While studies have documented electrophysiological and structural changes at synapses in response to precise manipulations of hippocampal slices, parallel biochemical and proteomic analyses were hampered by the lack of subcellular fractionation techniques applicable to starting tissue about three orders of magnitude smaller than that used in conventional protocols. Here, we describe a simple and convenient method for the preparation of PSD fractions from hippocampal slices and the identification of its components by proteomic techniques. The 'micro PSD fraction' obtained following two consecutive extractions of a synaptosomal fraction with Triton X-100 shows a significant enrichment in the marker protein PSD-95. Thin section electron microscopy shows PSDs similar to those observed in situ. However, other particulate material, especially myelin, and membrane vesicles are also present. The composition of the PSD fraction from hippocampal slices was analyzed by 2D LC/MS/MS. The proteomic approach which utilizes as little as 10 {mu}g total protein allowed the identification of >100 proteins. Many of the proteins detected in the fraction are the same as those identified in conventional PSD preparations including specialized PSD-scaffolding proteins, signaling molecules, cytoskeletal elements as well as certain contaminants. The results show the feasibility of the preparation of a PSD fraction from hippocampal slices of reasonable purity and of sufficient yield for proteomic analyses. In addition, we show that further purification of PSDs is possible using magnetic beads coated with a PSD-95 antibody.

  19. Thermal dependence of neural activity in the hamster hippocampal slice preparation

    NASA Technical Reports Server (NTRS)

    Horowitz, J. M.; Thomas, M. P.; Eckerman, P.

    1987-01-01

    1. Neural activity was recorded in an in vitro hamster hippocampal slice preparation while the temperature of the Ringer's solution bathing in the slice was controlled at selected levels. 2. The amplitude of the population spike (action potentials from a group of pyramidal cells) was measured as bath temperature was lowered from 35 degrees C to temperatures where a response could not be evoked. 3. Plots of population spike amplitude versus temperature have bell-shaped curves. The population spikes increased in amplitude as temperature was lowered from 35 degrees C, reached a peak amplitude between 25 and 20 degrees C, and then decreased until a response could not be evoked when temperature was further lowered. 4. These in vitro results obtained in the slice preparation are related to in vivo hippocampal studies. Results are interpreted as consistent with the proposal reviewed here that neural activity in the hippocampus plays a role at specific stages of entrance into and arousal from hibernation.

  20. Chronic Glucocorticoids Increase Hippocampal Vulnerability to Neurotoxicity under Conditions That Produce CA3 Dendritic Retraction But Fail to Impair Spatial Recognition Memory

    PubMed Central

    Conrad, Cheryl D.; McLaughlin, Katie J.; Harman, James S.; Foltz, Cainan; Wieczorek, Lindsay; Lightner, Elizabeth; Wright, Ryan L.

    2007-01-01

    We previously found that chronic stress conditions producing CA3 dendritic retraction and spatial memory deficits make the hippocampus vulnerable to the neurotoxin ibotenic acid (IBO). The purpose of this study was to determine whether exposure to chronic corticosterone (CORT) under conditions that produce CA3 dendritic retraction would enhance CA3 susceptibility to IBO. Male Sprague Dawley rats were chronically treated for 21 d with CORT in drinking water (400 μg/ml), and half were given daily injections of phenytoin (40 mg/kg), an antiepileptic drug that prevents CA3 dendritic retraction. Three days after treatments stopped, IBO was infused into the CA3 region. Conditions producing CA3 dendritic retraction (CORT and vehicle) exacerbated IBO-induced CA3 damage compared with conditions in which CA3 dendritic retraction was not observed (vehicle and vehicle, vehicle and phenytoin, CORT and phenytoin). Additionally, spatial recognition memory was assessed using the Y-maze, revealing that conditions producing CA3 dendritic retraction failed to impair spatial recognition memory. Furthermore, CORT levels in response to a potentially mild stressor (injection and Y-maze exposure) stayed at basal levels and failed to differ among key groups (vehicle and vehicle, CORT and vehicle, CORT and phenytoin), supporting the interpretations that CORT levels were unlikely to have been elevated during IBO infusion and that the neuroprotective actions of phenytoin were not through CORT alterations. These data are the first to show that conditions with prolonged glucocorticoid elevations leading to structural changes in hippocampal dendritic arbors can make the hippocampus vulnerable to neurotoxic challenges. These findings have significance for many disorders with elevated glucocorticoids that include depression, schizophrenia, Alzheimer’s disease, and Cushing’s disease. PMID:17670974

  1. Adaptation of Microplate-based Respirometry for Hippocampal Slices and Analysis of Respiratory Capacity

    PubMed Central

    Schuh, Rosemary A.; Clerc, Pascaline; Hwang, Hyehyun; Mehrabian, Zara; Bittman, Kevin; Chen, Hegang; Polster, Brian M.

    2011-01-01

    Multiple neurodegenerative disorders are associated with altered mitochondrial bioenergetics. Although mitochondrial O2 consumption is frequently measured in isolated mitochondria, isolated synaptic nerve terminals (synaptosomes), or cultured cells, the absence of mature brain circuitry is a remaining limitation. Here we describe the development of a method that adapts the Seahorse Extracellular Flux Analyzer (XF24) for the microplate-based measurement of hippocampal slice O2 consumption. As a first evaluation of the technique, we compared whole slice bioenergetics to previous measurements made with synaptosomes or cultured neurons. We found that mitochondrial respiratory capacity and O2 consumption coupled to ATP synthesis could be estimated in cultured or acute hippocampal slices with preserved neural architecture. Mouse organotypic hippocampal slices oxidizing glucose displayed mitochondrial O2 consumption that was well-coupled, as determined by the sensitivity to the ATP synthase inhibitor oligomycin. However stimulation of respiration by uncoupler was modest (<120% of basal respiration) compared to previous measurements in cells or synaptosomes, although enhanced slightly (to ~150% of basal respiration) by the acute addition of the mitochondrial complex I-linked substrate pyruvate. These findings suggest a high basal utilization of respiratory capacity in slices and a limitation of glucose-derived substrate for maximal respiration. The improved throughput of microplate-based hippocampal respirometry over traditional O2 electrode-based methods is conducive to neuroprotective drug screening. When coupled with cell type-specific pharmacology or genetic manipulations, the ability to efficiently measure O2 consumption from whole slices should advance our understanding of mitochondrial roles in physiology and neuropathology. PMID:21520220

  2. [Alteration of neural oscillations in hippocampal CA3 area in the fast avoidance response rat before and after electric shock avoidance training].

    PubMed

    Wang, Wei-Wei; Wang, Dan-Dan; Wang, Dan; Guan, Yan; Tang, Ying-Ying; Ye, Zheng; Li, Jing; Li, Min; Zhu, Zai-Man; Pan, Qun-Wan

    2015-10-25

    The purpose of the present study is to explore the relationship of spatial learning ability and specific electrical activities of neural oscillations in the rat. The fast and general avoidance response groups were selected on the basis of the animals' responses to the electric shock in Y type maze, and their local field potentials (LFPs) of hippocampal CA3 area were recorded by wireless telemetry before and after shock avoidance training, respectively. The components of neural oscillations related to spatial identifying and learning ability were analyzed. The results showed that, compared with the general avoidance response group, the fast avoidance response group did not show any differences of LFPs in hippocampal CA3 area before electric shock avoidance trial, but showed significantly increased percentages of 0-10 Hz and 30-40 Hz rhythm in right hippocampal CA3 area after the shock avoidance training (P < 0.01 or P < 0.05). Fast Fourier transform showed that percentage increase of 0-10 Hz band occurred mainly in θ (3-7 Hz) frequency, and 30-40 Hz frequency change was equivalent to the γ1 band. Furthermore, compared with those before training, only the percentages of β, β2 (20-30 Hz) and γ1 rhythm increased (P < 0.01 or P < 0.05) in fast avoidance response rats after training, while the θ rhythm percentage remained unchanged. In contrast, θ rhythm percentage and the large amplitude (intensity: +2.5 - -2.5 db) θ waves in right CA3 area of general avoidance response rats were significantly reduced after training (P < 0.01). These results suggest that the increased percentages of β2 and γ1 rhythm and high-level (unchanged) percentage of θ rhythm in the right hippocampus CA3 area might be related to strong spatial cognition ability of fast avoidance response rats. PMID:26490066

  3. Modification of hippocampal excitability in brain slices pretreated with a low nanomolar concentration of Zn2+.

    PubMed

    Takeda, Atsushi; Shakushi, Yukina; Tamano, Haruna

    2015-11-01

    Synaptic Zn2+ homeostasis may be changed during brain slice preparation. However, much less attention has been paid to Zn2+ in artificial cerebrospinal fluid (ACSF) used for slice experiments than has been paid to Ca2+ . The present study assesses addition of Zn2+ to ACSF, focused on hippocampal excitability after acute brain slice preparation. When the static levels of intracellular Zn2+ and Ca2+ were compared between brain slices prepared with conventional ACSF without Zn2+ and those pretreated with ACSF containing 20 nM ZnCl2 for 1 hr, both levels were almost the same. On the other hand, intracellular Ca2+ levels were significantly increased in the stratum lucidum of the control brain slices after stimulation with high K+, although the increase was significantly suppressed by the pretreatment with ACSF containing Zn2+, suggesting that neuronal excitation is enhanced in brain slices prepared with ACSF without Zn2+. The increase in extracellular Zn2+ level, an index of glutamate release, after stimulation with high K+ was also significantly suppressed by pretreatment with ACSF containing Zn2+. When mossy fiber excitation was assessed in brain slices with FM4-64, an indicator of presynaptic activity, attenuation of FM 4-64 fluorescence based on presynaptic activity was suppressed in the stratum lucidum of brain slices pretreated with ACSF containing Zn2+. The present study indicates that hippocampal excitability is enhanced in brain slices prepared with ACSF without Zn2+. It is likely that a low nanomolar concentration of Zn2+ is necessary for ACSF. PMID:26268632

  4. A multi-slice recording system for stable late phase hippocampal long-term potentiation experiments.

    PubMed

    Kroker, Katja Sabine; Rosenbrock, Holger; Rast, Georg

    2011-01-15

    A major challenge in neuroscience is identifying the cellular and molecular processes underlying learning and memory formation. In the past decades, significant progress has been made in understanding cellular and synaptic mechanisms underlying hippocampal learning and memory using long-term potentiation (LTP) experiments in brain slices as a model system. To expedite LTP measurements it is helpful to further optimize such recording systems. Here, we describe a modification of a multi-slice recording system (SliceMaster, Scientifica Limited, East Sussex, UK) that allows absolutely stable measurements of field excitatory postsynaptic potentials (fEPSPs) for up to 8 h in up to eight slices simultaneously. The software Notocord(®) was used for on-line data acquisition and to control the digital pattern generator which can generate different patterns for slice stimulation, inducing different types of LTP. Moreover, in contrast to common gravity-driven perfusion systems, a Pumped Perfusion System was employed to recycle drug solutions applied to the hippocampal slice. In addition, slices were positioned on two stacked grids for optimal recording of fEPSPs. These two stacked grids were placed in the measuring chambers allowing recordings for several hours without any perturbances. In summary, this modified slice-recording system improves throughput and allows for better statistical design, increases number of used slices per animal and enables very robust LTP measurements for up to 7 h. Hence, this system is suitable not only to investigate molecular mechanisms underlying the late phase of LTP, but also to screen candidate compounds in the context of drug discovery. PMID:21087635

  5. Repeating Spatial-Temporal Motifs of CA3 Activity Dependent on Engineered Inputs from Dentate Gyrus Neurons in Live Hippocampal Networks

    PubMed Central

    Bhattacharya, Aparajita; Desai, Harsh; DeMarse, Thomas B.; Wheeler, Bruce C.; Brewer, Gregory J.

    2016-01-01

    Anatomical and behavioral studies, and in vivo and slice electrophysiology of the hippocampus suggest specific functions of the dentate gyrus (DG) and the CA3 subregions, but the underlying activity dynamics and repeatability of information processing remains poorly understood. To approach this problem, we engineered separate living networks of the DG and CA3 neurons that develop connections through 51 tunnels for axonal communication. Growing these networks on top of an electrode array enabled us to determine whether the subregion dynamics were separable and repeatable. We found spontaneous development of polarized propagation of 80% of the activity in the native direction from DG to CA3 and different spike and burst dynamics for these subregions. Spatial-temporal differences emerged when the relationships of target CA3 activity were categorized with to the number and timing of inputs from the apposing network. Compared to times of CA3 activity when there was no recorded tunnel input, DG input led to CA3 activity bursts that were 7× more frequent, increased in amplitude and extended in temporal envelope. Logistic regression indicated that a high number of tunnel inputs predict CA3 activity with 90% sensitivity and 70% specificity. Compared to no tunnel input, patterns of >80% tunnel inputs from DG specified different patterns of first-to-fire neurons in the CA3 target well. Clustering dendrograms revealed repeating motifs of three or more patterns at up to 17 sites in CA3 that were importantly associated with specific spatial-temporal patterns of tunnel activity. The number of these motifs recorded in 3 min was significantly higher than shuffled spike activity and not seen above chance in control networks in which CA3 was apposed to CA3 or DG to DG. Together, these results demonstrate spontaneous input-dependent repeatable coding of distributed activity in CA3 networks driven by engineered inputs from DG networks. These functional configurations at measured times

  6. Dithiothreitol elicits epileptiform activity in CA1 of the guinea pig hippocampal slice

    SciTech Connect

    Tolliver, J.M.; Pellmar, T.C.

    1987-01-01

    Dithiothreitol (DTT) is a sulfhydryl reducing agent used as a radioprotectant. Exposure of hippocampal slices, for 30 min to 0.5 micromoles DTT irreversibly increased the orthodromic population spike amplitude, promoted repetitive firing and induced spontaneous epileptiform activity in the CA1 subfield. The same concentration of the oxidized form of DTT did not increase hippocampal excitability. Although the slope of the population synaptic response to afferent stimulation (popPSP) was unchanged by DTT, the duration of the popPSP was prolonged. Recurrent inhibition was unaffected. DTT probably exerts its effects through an irreversible chemical reaction with cellular components. Possible mechanisms of DTT-induced epileptiform activity are discussed.

  7. Effects of Blast Overpressure on Neurons and Glial Cells in Rat Organotypic Hippocampal Slice Cultures

    PubMed Central

    Miller, Anna P.; Shah, Alok S.; Aperi, Brandy V.; Budde, Matthew D.; Pintar, Frank A.; Tarima, Sergey; Kurpad, Shekar N.; Stemper, Brian D.; Glavaski-Joksimovic, Aleksandra

    2015-01-01

    Due to recent involvement in military conflicts, and an increase in the use of explosives, there has been an escalation in the incidence of blast-induced traumatic brain injury (bTBI) among US military personnel. Having a better understanding of the cellular and molecular cascade of events in bTBI is prerequisite for the development of an effective therapy that currently is unavailable. The present study utilized organotypic hippocampal slice cultures (OHCs) exposed to blast overpressures of 150 kPa (low) and 280 kPa (high) as an in vitro bTBI model. Using this model, we further characterized the cellular effects of the blast injury. Blast-evoked cell death was visualized by a propidium iodide (PI) uptake assay as early as 2 h post-injury. Quantification of PI staining in the cornu Ammonis 1 and 3 (CA1 and CA3) and the dentate gyrus regions of the hippocampus at 2, 24, 48, and 72 h following blast exposure revealed significant time dependent effects. OHCs exposed to 150 kPa demonstrated a slow increase in cell death plateauing between 24 and 48 h, while OHCs from the high-blast group exhibited a rapid increase in cell death already at 2 h, peaking at ~24 h post-injury. Measurements of lactate dehydrogenase release into the culture medium also revealed a significant increase in cell lysis in both low- and high-blast groups compared to sham controls. OHCs were fixed at 72 h post-injury and immunostained for markers against neurons, astrocytes, and microglia. Labeling OHCs with PI, neuronal, and glial markers revealed that the blast-evoked extensive neuronal death and to a lesser extent loss of glial cells. Furthermore, our data demonstrated activation of astrocytes and microglial cells in low- and high-blasted OHCs, which reached a statistically significant difference in the high-blast group. These data confirmed that our in vitro bTBI model is a useful tool for studying cellular and molecular changes after blast exposure. PMID:25729377

  8. Cariprazine delays ouabain-evoked epileptiform spikes and loss of activity in rat hippocampal slices.

    PubMed

    El-Mallakh, Rif S; Payne, Ralphiel S; Schurr, Avital; Gao, Yonglin; Lei, Zhemin; Kiss, Béla; Gyertyán, István; Adham, Nika

    2015-09-30

    In the only bipolar cycling in vitro model, rat hippocampal slices are treated with the sodium pump inhibitor ouabain, which induces epileptiform activity, followed by refractory activity loss that recovers and cycles back to epileptiform activity. Thus, clinical cycling seen in patients with bipolar disorder is modeled on a cellular level as alternating hyperactivity and hypoactivity interspersed with normal activity. In this study, we tested the ability of cariprazine a new antipsychotic candidate to block ouabain-induced changes in rat hippocampal slices. Cycling of population spikes and epileptiform bursts was evoked using an extracellular stimulation electrode located in the Schaeffer collaterals of 400-µm-thick rat hippocampal slices treated with ouabain (3.3μM) alone or in combination with cariprazine (1, 5, 25, and 50µM). Responses were recorded using an extracellular electrode placed in the cell body layer of the CA1 region. Cariprazine 25 and 50µM delayed ouabain-induced epileptiform burst onset and subsequent activity loss. Lower cariprazine concentrations were ineffective. Cariprazine delays the onset of ouabain-induced epileptiform bursts and the loss of spiking activity similarly to that previously demonstrated with the mood stabilizer lithium. These results suggest that cariprazine may have therapeutic potential for treatment of bipolar disorder. PMID:26160196

  9. Parkia biglobosa Improves Mitochondrial Functioning and Protects against Neurotoxic Agents in Rat Brain Hippocampal Slices

    PubMed Central

    Komolafe, Kayode; Olaleye, Tolulope M.; Seeger, Rodrigo L.; Carvalho, Fabiano B.; Boligon, Aline A.; Athayde, Margareth L.; Klimaczewski, Claudia V.; Akindahunsi, Akintunde A.; Rocha, Joao B. T.

    2014-01-01

    Objective. Methanolic leaf extracts of Parkia biglobosa, PBE, and one of its major polyphenolic constituents, catechin, were investigated for their protective effects against neurotoxicity induced by different agents on rat brain hippocampal slices and isolated mitochondria. Methods. Hippocampal slices were preincubated with PBE (25, 50, 100, or 200 µg/mL) or catechin (1, 5, or 10 µg/mL) for 30 min followed by further incubation with 300 µM H2O2, 300 µM SNP, or 200 µM PbCl2 for 1 h. Effects of PBE and catechin on SNP- or CaCl2-induced brain mitochondrial ROS formation and mitochondrial membrane potential (ΔΨm) were also determined. Results. PBE and catechin decreased basal ROS generation in slices and blunted the prooxidant effects of neurotoxicants on membrane lipid peroxidation and nonprotein thiol contents. PBE rescued hippocampal cellular viability from SNP damage and caused a significant boost in hippocampus Na+, K+-ATPase activity but with no effect on the acetylcholinesterase activity. Both PBE and catechin also mitigated SNP- or CaCl2-dependent mitochondrial ROS generation. Measurement by safranine fluorescence however showed that the mild depolarization of the ΔΨm by PBE was independent of catechin. Conclusion. The results suggest that the neuroprotective effect of PBE is dependent on its constituent antioxidants and mild mitochondrial depolarization propensity. PMID:25177688

  10. In Vitro Manganese Exposure Disrupts MAPK Signaling Pathways in Striatal and Hippocampal Slices from Immature Rats

    PubMed Central

    Peres, Tanara Vieira; Pedro, Daniela Zótico; de Cordova, Fabiano Mendes; Lopes, Mark William; Gonçalves, Filipe Marques; Mendes-de-Aguiar, Cláudia Beatriz Nedel; Walz, Roger; Farina, Marcelo; Aschner, Michael; Leal, Rodrigo Bainy

    2013-01-01

    The molecular mechanisms mediating manganese (Mn)-induced neurotoxicity, particularly in the immature central nervous system, have yet to be completely understood. In this study, we investigated whether mitogen-activated protein kinases (MAPKs) and tyrosine hydroxylase (TH) could represent potential targets of Mn in striatal and hippocampal slices obtained from immature rats (14 days old). The aim of this study was to evaluate if the MAPK pathways are modulated after subtoxic Mn exposure, which do not significantly affect cell viability. The concentrations of manganese chloride (MnCl2; 10–1,000 μM) caused no change in cell viability in slices exposed for 3 or 6 hours. However, Mn exposure significantly increased extracellular signal-regulated kinase (ERK) 1/2, as well as c-Jun N-terminal kinase (JNK) 1/2/3 phosphorylation at both 3 and 6 hours incubations, in both brain structures. Furthermore, Mn exposure did not change the total content or phosphorylation of TH at the serine 40 site in striatal slices. Thus, Mn at concentrations that do not disrupt cell viability causes activation of MAPKs (ERK1/2 and JNK1/2/3) in immature hippocampal and striatal slices. These findings suggest that altered intracellular MAPKs signaling pathways may represent an early event concerning the effects of Mn in the immature brain. PMID:24324973

  11. Activity-dependent downregulation of D-type K+ channel subunit Kv1.2 in rat hippocampal CA3 pyramidal neurons.

    PubMed

    Hyun, Jung Ho; Eom, Kisang; Lee, Kyu-Hee; Ho, Won-Kyung; Lee, Suk-Ho

    2013-11-15

    The intrinsic excitability of neurons plays a critical role in the encoding of memory at Hebbian synapses and in the coupling of synaptic inputs to spike generation. It has not been studied whether somatic firing at a physiologically relevant frequency can induce intrinsic plasticity in hippocampal CA3 pyramidal cells (CA3-PCs). Here, we show that a conditioning train of 20 action potentials (APs) at 10 Hz causes a persistent reduction in the input conductance and an acceleration of the AP onset time in CA3-PCs, but not in CA1-PCs. Induction of such long-term potentiation of intrinsic excitability (LTP-IE) was accompanied by a reduction in the D-type K(+) current, and was abolished by the inhibition of endocytosis or protein tyrosine kinase (PTK). Consistently, the CA3-PCs from Kv1.2 knock-out mice displayed no LTP-IE with the same conditioning. Furthermore, the induction of LTP-IE depended on the back-propagating APs (bAPs) and intact distal apical dendrites. These results indicate that LTP-IE is mediated by the internalization of Kv1.2 channels from the distal regions of apical dendrites, which is triggered by bAP-induced dendritic Ca(2+) signalling and the consequent activation of PTK. PMID:23981714

  12. Effect of intermittent hypoxia on long-term potentiation in rat hippocampal slices.

    PubMed

    Payne, Ralphiel S; Goldbart, Aviv; Gozal, David; Schurr, Avital

    2004-12-17

    Intermittent hypoxia (IH) during sleep has been shown to induce apoptosis in a time-dependent manner and spatial learning deficits in adult rats. Recently, we have demonstrated that IH induced significant decreases in Ser-133-phosphorylated cAMP-response element-binding protein (pCREB) without changes in total CREB. The expression of cleaved caspase 3 in the hippocampal CA1, a marker of apoptosis, peaked at 3 days of IH and returned to normoxic values at 14 days of IH. In addition, biphasic changes in spatial task learning were correlated with the CREB phosphorylation time course. In the present study, the rat hippocampal slice preparation was used to evaluate the ability to induce and maintain a CA1 population spike long-term potentiation (PS-LTP) in room air (RA)-maintained and IH-exposed rats. A significant decrease in the ability to sustain PS-LTP for 15 min in slices prepared from IH-exposed rats for either 3 days (34% of total) or 7 days (51% of total) as compared to slices prepared from RA-maintained rats (76% of total) was observed. These results suggest that the diminishment in the ability of neuronal tissue to express and sustain PS-LTP is correlated with previously reported biphasic changes in CREB phosphorylation and programmed cell death. PMID:15542074

  13. Spatial memory training induces morphological changes detected by manganese-enhanced MRI in the hippocampal CA3 mossy fiber terminal zone.

    PubMed

    Zhang, Binbin; Chuang, Kai-Hsiang; Tjio, Ci'en; Chen, Way Cherng; Sheu, Fwu-Shan; Routtenberg, Aryeh

    2016-03-01

    Hippocampal mossy fibers (MFs) can show plasticity of their axon terminal arbor consequent to learning a spatial memory task. Such plasticity is seen as translaminar sprouting from the stratum lucidum (SL) of CA3 into the stratum pyramidale (SP) and the stratum oriens (SO). However, the functional role of this presynaptic remodeling is still obscure. In vivo imaging that allows longitudinal observation of such remodeling could provide a deeper understanding of this presynaptic growth phenomenon as it occurs over time. Here we used manganese-enhanced magnetic resonance imaging (MEMRI), which shows a high-contrast area that co-localizes with the MFs. This technique was applied in the detection of learning-induced MF plasticity in two strains of rats. Quantitative analysis of a series of sections in the rostral dorsal hippocampus showed increases in the CA3a' area in MEMRI of trained Wistar rats consistent with the increased SO+SP area seen in the Timm's staining. MF plasticity was not seen in the trained Lister-Hooded rats in either MEMRI or in Timm's staining. This indicates the potential of MEMRI for revealing neuro-architectures and plasticity of the hippocampal MF system in vivo in longitudinal studies. PMID:26254115

  14. Intrinsic Hippocampal Excitability Changes of Opposite Signs and Different Origins in CA1 and CA3 Pyramidal Neurons Underlie Aging-Related Cognitive Deficits

    PubMed Central

    Oh, M. Matthew; Simkin, Dina; Disterhoft, John F.

    2016-01-01

    Aging-related cognitive deficits have been attributed to dysfunction of neurons due to failures at synaptic or intrinsic loci, or both. Given the importance of the hippocampus for successful encoding of memory and that the main output of the hippocampus is via the CA1 pyramidal neurons, much of the research has been focused on identifying the aging-related changes of these CA1 pyramidal neurons. We and others have discovered that the postburst afterhyperpolarization (AHP) following a train of action potentials is greatly enlarged in CA1 pyramidal neurons of aged animals. This enlarged postburst AHP is a significant factor in reducing the intrinsic excitability of these neurons, and thus limiting their activity in the neural network during learning. Based on these data, it has largely been thought that aging-related cognitive deficits are attributable to reduced activity of pyramidal neurons. However, recent in vivo and ex vivo studies provide compelling evidence that aging-related deficits could also be due to a converse change in CA3 pyramidal neurons, which show increased activity with aging. In this review, we will incorporate these recent findings and posit that an interdependent dynamic dysfunctional change occurs within the hippocampal network, largely due to altered intrinsic excitability in CA1 and CA3 hippocampal pyramidal neurons, which ultimately leads to the aging-related cognitive deficits. PMID:27375440

  15. Long-lasting desynchronization in rat hippocampal slice induced by coordinated reset stimulation

    SciTech Connect

    Tass, P. A.; Barnikol, U. B.; Silchenko, A. N.; Hauptmann, C.; Speckmann, E.-J.

    2009-07-15

    In computational models it has been shown that appropriate stimulation protocols may reshape the connectivity pattern of neural or oscillator networks with synaptic plasticity in a way that the network learns or unlearns strong synchronization. The underlying mechanism is that a network is shifted from one attractor to another, so that long-lasting stimulation effects are caused which persist after the cessation of stimulation. Here we study long-lasting effects of multisite electrical stimulation in a rat hippocampal slice rendered epileptic by magnesium withdrawal. We show that desynchronizing coordinated reset stimulation causes a long-lasting desynchronization between hippocampal neuronal populations together with a widespread decrease in the amplitude of the epileptiform activity. In contrast, periodic stimulation induces a long-lasting increase in both synchronization and amplitude.

  16. Tributyltin induces oxidative stress and neuronal injury by inhibiting glutathione S-transferase in rat organotypic hippocampal slice cultures.

    PubMed

    Ishihara, Yasuhiro; Kawami, Tomohito; Ishida, Atsuhiko; Yamazaki, Takeshi

    2012-06-01

    Tributyltin (TBT) has been used as a heat stabilizer, agricultural pesticide and antifouling agents on ships, boats and fish-farming nets; however, the neurotoxicity of TBT has recently become a concern. TBT is suggested to stimulate the generation of reactive oxygen species (ROS) inside cells. The aim of this study was to determine the mechanism of neuronal oxidative injury induced by TBT using rat organotypic hippocampal slice cultures. The treatment of rat hippocampal slices with TBT induced ROS production, lipid peroxidation and cell death. Pretreatment with antioxidants such as superoxide dismutase, catalase or trolox, suppressed the above phenomena induced by TBT, indicating that TBT elicits oxidative stress in hippocampal slices, which causes neuronal cell death. TBT dose-dependently inhibited glutathione S-transferase (GST), but not glutathione peroxidase or glutathione reductase in the cytosol of rat hippocampus. The treatment of hippocampal slices with TBT decreased the GST activity. Pretreatment with reduced glutathione attenuated the reduction of GST activity and cell death induced by TBT, indicating that the decrease in GST activity by TBT is involved in hippocampal cell death. When hippocampal slices were treated with sulforaphane, the expression and activity of GST were increased. Notably, TBT-induced oxidative stress and cell death were significantly suppressed by pretreatment with sulforaphane. These results indicate that GST inhibition could contribute, at least in part, to the neuronal cell death induced by TBT in hippocampal slices. This study is the first report to show the link between neuronal oxidative injury and the GST inhibition elicited by TBT. PMID:22449404

  17. Phase dependency of long-term potentiation induction during the intermittent bursts of carbachol-induced β oscillation in rat hippocampal slices

    PubMed Central

    Nishimura, Motoshi; Nakatsuka, Hiroki; Natsume, Kiyohisa

    2012-01-01

    The rodent hippocampus possesses theta (θ) and beta (β) rhythms, which occur intermittently as bursts. Both rhythms are related to spatial memory processing in a novel environment. θ rhythm is related to spatial memory encoding process. β rhythm is related to the match/mismatch process. In the match/mismatch process, rodent hippocampus detects a representation matching sensory inputs of the current place among the retrieved internal representations of places. Long-term synaptic potentiation (LTP) is induced in both processes. The cholinergic agent carbachol induces intermittent θ and β oscillations in in vitro slices similar to in vivo bursts. LTP is facilitated during the generation of θ oscillation, suggesting that the facilitation of LTP is dependent upon the phases of intermittent burst (burst phases) of the oscillation. However, whether this is the case for β oscillation has not yet been studied. In the present study, LTP-inducing θ-burst stimulation was administered at the different burst phases of carbachol-induced β oscillations (CIBO), and the synaptic changes were measured at CA3-CA3 pyramidal cell synapses (CA3 synapse) and at CA3-CA1 pyramidal cell synapses (CA1 synapse). At the CA3 synapse, the largest magnitude of LTP was induced at the late burst phases of CIBO. At the CA1 synapse, LTP was induced only at the late burst phases. Modulation of LTP was suppressed when CIBO was blocked by the application of atropine at both synapses. The results suggest that the bursts of hippocampal β rhythm can determine the optimal temporal period for completing with the match/mismatch process.

  18. Lactate Effectively Covers Energy Demands during Neuronal Network Activity in Neonatal Hippocampal Slices

    PubMed Central

    Ivanov, Anton; Mukhtarov, Marat; Bregestovski, Piotr; Zilberter, Yuri

    2011-01-01

    Although numerous experimental data indicate that lactate is efficiently used for energy by the mature brain, the direct measurements of energy metabolism parameters during neuronal network activity in early postnatal development have not been performed. Therefore, the role of lactate in the energy metabolism of neurons at this age remains unclear. In this study, we monitored field potentials and contents of oxygen and NAD(P)H in correlation with oxidative metabolism during intense network activity in the CA1 hippocampal region of neonatal brain slices. We show that in the presence of glucose, lactate is effectively utilized as an energy substrate, causing an augmentation of oxidative metabolism. Moreover, in the absence of glucose lactate is fully capable of maintaining synaptic function. Therefore, during network activity in neonatal slices, lactate can be an efficient energy substrate capable of sustaining and enhancing aerobic energy metabolism. PMID:21602909

  19. Muscarinic agonists and phorbol esters increase tyrosine phosphorylation of a 40-kilodalton protein in hippocampal slices

    SciTech Connect

    Stratton, K.R.; Worley, P.F.; Huganir, R.L.; Baraban, J.M. )

    1989-04-01

    The authors have used the hippocampal slice preparation to investigate the regulation of protein tyrosine phosphorylation in brain. After pharmacological treatment of intact slices, proteins were separated by electrophoresis, and levels of protein tyrosine phosphorylation were assessed by immunoblotting with specific anti-phosphotyrosine antibodies. Phorbol esters, activators of the serine- and threonine-phosphorylating enzyme protein kinase C, selectively increase tyrosine phosphorylation of a soluble protein with an apparent molecular mass of approximately 40 kilodaltons. Muscarinic agonists such as carbachol and oxotremorine M that strongly activate the inositol phospholipid system also increase tyrosine phosphorylation of this protein. Neurotransmitter activation of the inositol phospholipid system and protein kinase C appears to trigger a cascade leading to increased tyrosine phosphorylation.

  20. Ballistic labeling and dynamic imaging of astrocytes in organotypic hippocampal slice cultures.

    PubMed

    Benediktsson, Adrienne M; Schachtele, Scott J; Green, Steven H; Dailey, Michael E

    2005-01-30

    Protoplasmic astrocytes in mammalian CNS tissues in vivo have a highly complex 3D morphology, but in dissociated cell cultures they often assume a flattened, fibroblast-like morphology bearing only a few, simple processes. By fluorescent labeling and confocal reconstruction we show that many astrocytes in organotypic hippocampal slice cultures exhibit a more native complex cytoarchitecture. Although astrocytes at the surface of slice cultures show a reactive form with several thick glial fibrillary acidic protein (GFAP)-positive processes, astrocytes situated in deeper portions of tissue slices retain a highly complex 3D morphology with many fine spine- or veil-like protrusions. Dozens of astrocytes can be labeled in single slice cultures by gene gun-mediated ballistic delivery of gold or tungsten particles carrying cDNAs (Biolistics), lipophilic dyes (DiOlistics), or fluorescent intracellular calcium indicators (Calistics). Expression of a membrane-targeted form of eGFP (Lck-GFP) is superior to soluble eGFP for resolving fine astrocytic processes. Time-lapse confocal imaging of Lck-GFP transfected astrocytes or "calistically" labeled astrocytes show structural remodeling and calcium transients, respectively. This approach provides an in vitro system for investigating the functional architecture, development and dynamic remodeling of astrocytes and their relationships to neurons and glia in live mammalian brain tissues. PMID:15585287

  1. Investigation of Synaptic Tagging/Capture and Cross-capture using Acute Hippocampal Slices from Rodents

    PubMed Central

    Shetty, Mahesh Shivarama; Sharma, Mahima; Hui, Neo Sin; Dasgupta, Ananya; Gopinadhan, Suma; Sajikumar, Sreedharan

    2015-01-01

    Synaptic tagging and capture (STC) and cross-tagging are two important mechanisms at cellular level that explain how synapse-specificity and associativity is achieved in neurons within a specific time frame. These long-term plasticity-related processes are the leading candidate models to study the basis of memory formation and persistence at the cellular level. Both STC and cross-tagging involve two serial processes: (1) setting of the synaptic tag as triggered by a specific pattern of stimulation, and (2) synaptic capture, whereby the synaptic tag interacts with newly synthesized plasticity-related proteins (PRPs). Much of the understanding about the concepts of STC and cross-tagging arises from the studies done in CA1 region of the hippocampus and because of the technical complexity many of the laboratories are still unable to study these processes. Experimental conditions for the preparation of hippocampal slices and the recording of stable late-LTP/LTD are extremely important to study synaptic tagging/cross-tagging. This video article describes the experimental procedures to study long-term plasticity processes such as STC and cross-tagging in the CA1 pyramidal neurons using stable, long-term field-potential recordings from acute hippocampal slices of rats. PMID:26381286

  2. Investigation of Synaptic Tagging/Capture and Cross-capture using Acute Hippocampal Slices from Rodents.

    PubMed

    Shetty, Mahesh Shivarama; Sharma, Mahima; Hui, Neo Sin; Dasgupta, Ananya; Gopinadhan, Suma; Sajikumar, Sreedharan

    2015-01-01

    Synaptic tagging and capture (STC) and cross-tagging are two important mechanisms at cellular level that explain how synapse-specificity and associativity is achieved in neurons within a specific time frame. These long-term plasticity-related processes are the leading candidate models to study the basis of memory formation and persistence at the cellular level. Both STC and cross-tagging involve two serial processes: (1) setting of the synaptic tag as triggered by a specific pattern of stimulation, and (2) synaptic capture, whereby the synaptic tag interacts with newly synthesized plasticity-related proteins (PRPs). Much of the understanding about the concepts of STC and cross-tagging arises from the studies done in CA1 region of the hippocampus and because of the technical complexity many of the laboratories are still unable to study these processes. Experimental conditions for the preparation of hippocampal slices and the recording of stable late-LTP/LTD are extremely important to study synaptic tagging/cross-tagging. This video article describes the experimental procedures to study long-term plasticity processes such as STC and cross-tagging in the CA1 pyramidal neurons using stable, long-term field-potential recordings from acute hippocampal slices of rats. PMID:26381286

  3. Calcium-activated afterhyperpolarizations regulate synchronization and timing of epileptiform bursts in hippocampal CA3 pyramidal neurons.

    PubMed

    Fernández de Sevilla, David; Garduño, Julieta; Galván, Emilio; Buño, Washington

    2006-12-01

    Calcium-activated potassium conductances regulate neuronal excitability, but their role in epileptogenesis remains elusive. We investigated in rat CA3 pyramidal neurons the contribution of the Ca(2+)-activated K(+)-mediated afterhyperpolarizations (AHPs) in the genesis and regulation of epileptiform activity induced in vitro by 4-aminopyridine (4-AP) in Mg(2+)-free Ringer. Recurring spike bursts terminated by prolonged AHPs were generated. Burst synchronization between CA3 pyramidal neurons in paired recordings typified this interictal-like activity. A downregulation of the medium afterhyperpolarization (mAHP) paralleled the emergence of the interictal-like activity. When the mAHP was reduced or enhanced by apamin and EBIO bursts induced by 4-AP were increased or blocked, respectively. Inhibition of the slow afterhyperpolarization (sAHP) with carbachol, t-ACPD, or isoproterenol increased bursting frequency and disrupted burst regularity and synchronization between pyramidal neuron pairs. In contrast, enhancing the sAHP by intracellular dialysis with KMeSO(4) reduced burst frequency. Block of GABA(A-B) inhibitions did not modify the abnormal activity. We describe novel cellular mechanisms where 1) the inhibition of the mAHP plays an essential role in the genesis and regulation of the bursting activity by reducing negative feedback, 2) the sAHP sets the interburst interval by decreasing excitability, and 3) bursting was synchronized by excitatory synaptic interactions that increased in advance and during bursts and decreased throughout the subsequent sAHP. These cellular mechanisms are active in the CA3 region, where epileptiform activity is initiated, and cooperatively regulate the timing of the synchronized rhythmic interictal-like network activity. PMID:16971683

  4. Topological organization of CA3-to-CA1 excitation.

    PubMed

    Hongo, Yoshie; Ogawa, Koichi; Takahara, Yuji; Takasu, Keiko; Royer, Sebastien; Hasegawa, Minoru; Sakaguchi, Gaku; Ikegaya, Yuji

    2015-09-01

    The CA1-projecting axons of CA3 pyramidal cells, called Schaffer collaterals, constitute one of the major information flow routes in the hippocampal formation. Recent anatomical studies have revealed the non-random structural connectivity between CA3 and CA1, but little is known regarding the functional connectivity (i.e. how CA3 network activity is functionally transmitted downstream to the CA1 network). Using functional multi-neuron calcium imaging of rat hippocampal slices, we monitored the spatiotemporal patterns of spontaneous CA3 and CA1 burst activity under pharmacological GABAergic blockade. We found that spatially clustered CA3 activity patterns were transformed into layered CA1 activity sequences. Specifically, synchronized bursts initiated from multiple hot spots in CA3 ensembles, and CA1 neurons located deeper in the pyramidal cell layer were recruited during earlier phases of the burst events. The order of these sequential activations was maintained across the bursts, but the sequence velocity varied depending on the inter-burst intervals. Thus, CA3 axons innervate CA1 neurons in a highly topographical fashion. PMID:26036915

  5. A guinea pig hippocampal slice model of organophosphate-induced seizure activity.

    PubMed

    Harrison, Patrick K; Sheridan, Robert D; Green, A Chris; Scott, Iain R; Tattersall, John E H

    2004-08-01

    Extracellular recording techniques have been used in the guinea pig hippocampal slice preparation to investigate the electrophysiological actions of the organophosphate (OP) anticholinesterase soman. When applied at a concentration of 100 nM, soman induced epileptiform activity in the CA1 region in approximately 75% of slices. This effect was mimicked by the anticholinesterases paraoxon (1 and 3 microM), physostigmine (30 microM), and neostigmine (30 microM), thus providing indirect evidence that the epileptiform response was mediated by elevated acetylcholine levels. Soman-induced bursting was inhibited by the muscarinic receptor antagonists atropine (concentrations tested, 0.1-10 microM), telenzepine (0.03-3 microM), AF-DX116 [11-(2-[(diethylamino)methyl]-1-piperidinyl acetyl)-5,11-dihydro-6H-pyrido 92.b-b) (1,4)-benzodiazepin-6-one] (0.3-300 microM), and biperiden (0.1-10 microM) and by the benzodiazepine anticonvulsants diazepam (3-30 microM) and midazolam (3-30 microM), but it was not inhibited by the nicotinic antagonists mecamylamine (30 microM) and methyllycaconitine (300 nM). In contrast to soman-induced epileptiform activity, bursting induced by the K(+) channel blocker 4-aminopyridine (30 microM), the adenosine A1 receptor antagonist 8-cyclopentyl-1,3-dipropylxanthine (30 nM) or perfusion with low Mg(2+) buffer was insensitive to atropine (10 microM). The ability of muscarinic antagonists and benzodiazepines to inhibit soman-induced epileptiform activity is in accordance with the in vivo pharmacology of soman-induced seizures and suggests that the guinea pig hippocampal slice preparation may provide a useful tool for the evaluation of novel anticonvulsant therapies for the treatment of seizures related to OP poisoning. PMID:15031302

  6. Effect of tolbutamide, glyburide and glipizide administered supraspinally on CA3 hippocampal neuronal cell death and hyperglycemia induced by kainic acid in mice.

    PubMed

    Kim, Chea-Ha; Park, Soo-Hyun; Sim, Yun-Beom; Kim, Sung-Su; Kim, Su-Jin; Lim, Su-Min; Jung, Jun-Sub; Suh, Hong-Won

    2014-05-20

    Sulfonylureas are widely used oral drugs for the treatment of type II diabetes mellitus. In the present study, the effects of sulfonylureas administered supraspinally on kainic acid (KA)-induced hippocampal neuronal cell death and hyperglycemia were studied in ICR mice. Mice were pretreated intracerebroventricularly (i.c.v.) with 30μg of tolbutamide, glyburide or glipizide for 10min and then, mice were administered i.c.v. with KA (0.1μg). The neuronal cell death in the CA3 region in the hippocampus was assessed 24h after KA administration and the blood glucose level was measured 30, 60, and 120min after KA administration. We found that i.c.v. pretreatment with tolbutamide, glyburide or glipizide attenuated the KA-induced neuronal cell death in CA3 region of the hippocampus and hyperglycemia. In addition, KA administered i.c.v. caused an elevation of plasma corticosterone level and a reduction of the plasma insulin level. The i.c.v. pretreatment with tolbutamide, glyburide or glipizide attenuated KA-induced increase of plasma corticosterone level. Furthermore, i.c.v. pretreatment with tolbutamide, glyburide or glipizide causes an elevation of plasma insulin level. Glipizide, but not tolbutamide or glyburide, pretreated i.c.v. caused a reversal of KA-induced hypoinsulinemic effect. Our results suggest that supraspinally administered tolbutamide, glyburide and glipizide exert a protective effect against KA-induced neuronal cells death in CA3 region of the hippocampus. The neuroprotective effect of tolbutamide, glyburide and glipizide appears to be mediated by lowering the blood glucose level induced by KA. PMID:24713348

  7. ALUMINUM DECREASES MUSCARINIC, ADRENERGIC, AND METABOTROPIC RECEPTOR-STIMULATED PHOSPHOINOSITIDE HYDROLYSIS IN HIPPOCAMPAL AND CORTICAL SLICES FROM RAT BRAIN

    EPA Science Inventory

    Effects of aluminum chloride (AlCl3) (0.1 to 1000 um) on inositol phosphate (IP) accumulation stimulated by carbachol (CARB), norepinephrine (NE) or quisqualate (QUIS) were examined in rat hippocampal and cortical slices. n the absence of agonist, only 1000 um AIC1 significantly ...

  8. Long-Term Potentiation by Theta-Burst Stimulation Using Extracellular Field Potential Recordings in Acute Hippocampal Slices.

    PubMed

    Abrahamsson, Therese; Lalanne, Txomin; Watt, Alanna J; Sjöström, P Jesper

    2016-01-01

    This protocol describes how to carry out theta-burst long-term potentiation (LTP) with extracellular field recordings in acute rodent hippocampal slices. This method is relatively simple and noninvasive and provides a way to sample many neurons simultaneously, making it suitable for applications requiring higher throughput than whole-cell recording. PMID:27250947

  9. Two different mechanisms underlie reversible, intrinsic optical signals in rat hippocampal slices.

    PubMed

    Fayuk, Dmitriy; Aitken, Peter G; Somjen, George G; Turner, Dennis A

    2002-04-01

    Intrinsic optical signals (IOSs) induced by synaptic stimulation and moderate hypotonic swelling in brain tissue slices consist of reduced light scattering and are usually attributed to cell swelling. During spreading depression (SD), however, light-scattering increases even though SD has been shown to cause strong cell swelling. To understand this phenomenon, we recorded extracellular voltage, light transmission (LT), which is inversely related to light scattering, and interstitial volume (ISV) simultaneously from the same site (stratum radiatum of CA1) in both interface and submerged hippocampal slices. As expected, moderate lowering of bath osmolarity caused concentration-dependent shrinkage of ISV and increase in LT, while increased osmolarity induced opposite changes in both variables. During severe hypotonia, however, after an initial increase of LT, the direction of the IOS reversed to a progressive decrease in spite of continuing ISV shrinkage. SD caused by hypotonia, by microinjection of high-K(+) solution, or by hypoxia, was associated with a pronounced LT decrease, during which ISV shrinkage indicated maximal cell swelling. If most of the extracellular Cl(-) was substituted by the impermeant anion methylsulfate and also in strongly hypertonic medium, the SD-related decrease in LT was suppressed and replaced by a monotonic increase. Nevertheless, the degree of ISV shrinkage was similar in low and in normal Cl(-) conditions. The optical signals and ISV changes were qualitatively identical in interface and submerged slices. We conclude that there are at least two mechanisms that underlie reversible optical responses in hippocampal slices. The first mechanism underlies light-scattering decrease (hence enhancing LT) when ISV shrinks (cell swelling) under synaptic stimulation and mild hypotonia. Similarly, as result of this mechanism, expansion of ISV (cell shrinkage) during mild hypertonia leads to an increased light scattering (and decreased LT). Thus

  10. Organotypic Hippocampal Slices as Models for Stroke and Traumatic Brain Injury.

    PubMed

    Li, Qian; Han, Xiaoning; Wang, Jian

    2016-08-01

    Organotypic hippocampal slice cultures (OHSCs) have been used as a powerful ex vivo model for decades. They have been used successfully in studies of neuronal death, microglial activation, mossy fiber regeneration, neurogenesis, and drug screening. As a pre-animal experimental phase for physiologic and pathologic brain research, OHSCs offer outcomes that are relatively closer to those of whole-animal studies than outcomes obtained from cell culture in vitro. At the same time, mechanisms can be studied more precisely in OHSCs than they can be in vivo. Here, we summarize stroke and traumatic brain injury research that has been carried out in OHSCs and review classic experimental applications of OHSCs and its limitations. PMID:26223803

  11. Stimulation of Anterior Thalamic Nuclei Protects Against Seizures and Neuronal Apoptosis in Hippocampal CA3 Region of Kainic Acid-induced Epileptic Rats

    PubMed Central

    Meng, Da-Wei; Liu, Huan-Guang; Yang, An-Chao; Zhang, Kai; Zhang, Jian-Guo

    2016-01-01

    Background: The antiepileptic effect of the anterior thalamic nuclei (ANT) stimulation has been demonstrated; however, its underlying mechanism remains unclear. The aim of this study was to investigate the effect of chronic ANT stimulation on hippocampal neuron loss and apoptosis. Methods: Sixty-four rats were divided into four groups: The control group, the kainic acid (KA) group, the sham-deep brain stimulation (DBS) group, and the DBS group. KA was used to induce epilepsy. Seizure count and latency to the first spontaneous seizures were calculated. Nissl staining was used to analyze hippocampal neuronal loss. Polymerase chain reaction and Western blotting were conducted to assess the expression of caspase-3 (Casp3), B-cell lymphoma-2 (Bcl2), and Bcl2-associated X protein (Bax) in the hippocampal CA3 region. One-way analysis of variance was used to determine the differences between the four groups. Results: The latency to the first spontaneous seizures in the DBS group was significantly longer than that in the KA group (27.50 ± 8.05 vs. 16.38 ± 7.25 days, P = 0.0005). The total seizure number in the DBS group was also significantly reduced (DBS vs. KA group: 11.75 ± 6.80 vs. 23.25 ± 7.72, P = 0.0002). Chronic ANT-DBS reduced neuronal loss in the hippocampal CA3 region (DBS vs. KA group: 23.58 ± 6.34 vs. 13.13 ± 4.00, P = 0.0012). After chronic DBS, the relative mRNA expression level of Casp3 was decreased (DBS vs. KA group: 1.18 ± 0.37 vs. 2.09 ± 0.46, P = 0.0003), and the relative mRNA expression level of Bcl2 was increased (DBS vs. KA group: 0.92 ± 0.21 vs. 0.48 ± 0.16, P = 0.0004). The protein expression levels of CASP3 (DBS vs. KA group: 1.25 ± 0.26 vs. 2.49 ± 0.38, P < 0.0001) and BAX (DBS vs. KA group: 1.57 ± 0.49 vs. 2.80 ± 0.63, P = 0.0012) both declined in the DBS group whereas the protein expression level of BCL2 (DBS vs. KA group: 0.78 ± 0.32 vs. 0.36 ± 0.17, P = 0.0086) increased in the DBS group. Conclusions: This study demonstrated

  12. Mechanisms underlying H(2)O(2)-mediated inhibition of synaptic transmission in rat hippocampal slices.

    PubMed

    Avshalumov, M V; Chen, B T; Rice, M E

    2000-11-01

    Hydrogen peroxide (H(2)O(2)) inhibits the population spike (PS) evoked by Schaffer collateral stimulation in hippocampal slices. Proposed mechanisms underlying this effect include generation of hydroxyl radicals (.OH) and inhibition of presynaptic Ca(2+) entry. We have examined these possible mechanisms in rat hippocampal slices. Inhibition of the evoked PS by H(2)O(2) was sharply concentration-dependent: 1.2 mM H(2)O(2) had no effect, whereas 1.5 and 2.0 mM H(2)O(2) reversibly depressed PS amplitude by roughly 80%. The iron chelator, deferoxamine (1 mM), and the endogenous.OH scavenger, ascorbate (400 microM), prevented PS inhibition, confirming.OH involvement. Isoascorbate (400 microM), which unlike ascorbate is not taken up by brain cells, also prevented PS inhibition, indicating an extracellular site of.OH generation or action. We then investigated whether H(2)O(2)-induced PS depression could be overcome by prolonged stimulation, which enhances Ca(2+) entry. During 5-s, 10-Hz trains under control conditions, PS amplitude increased to over 200% during the first three-four pulses, then stabilized. In the presence of H(2)O(2), PS amplitude was initially depressed, but began to recover after 2.5 s of stimulation, finally reaching 80% of the control maximum. In companion experiments, we assessed the effect of H(2)O(2) on presynaptic Ca(2+) entry by monitoring extracellular Ca(2+) concentration ([Ca(2+)](o)) during train stimulation in the presence of postsynaptic receptor blockers. Evoked [Ca(2+)](o) shifts were apparently unaltered by H(2)O(2), suggesting a lack of effect on Ca(2+) entry. Taken together, these findings suggest new ways in which reactive oxygen species (ROS) might act as signaling agents, specifically as modulators of synaptic transmission. PMID:11056187

  13. Long-term stimulation of mouse hippocampal slice culture on microelectrode array.

    PubMed

    van Bergen, A; Papanikolaou, T; Schuker, A; Möller, A; Schlosshauer, B

    2003-05-01

    To understand mechanisms of information processing, development and degeneration of the central nervous system, simultaneous multisite recording and stimulation have become extremely helpful. We have further developed the innovative approach to record from intact neural networks using planar microelectrode arrays (MEAs) with 60 substrate-integrated nano-columnar electrodes. To allow for long-term stimulation, mouse hippocampal tissue slices were immobilized onto MEAs and permanently moved between the gas and medium phase in a specifically designed tilting incubator that made it possible to electrically contact up to 90 MEAs with 5400 electrodes. After 2-3 weeks in vitro, histochemical staining, the intracellular microinjection of the fluorescent dye Alexa and the recording of spontaneous activity revealed in vivo-like characteristics of the organotypically cultured tissue. The feasibility of long-term stimulation during culturing was demonstrated with a low frequency paradigm. 0.003 Hz stimulation over a 16 h period resulted in a significant decline of field potentials and population spikes in two identified hippocampal subregions. Control experiments revealed that this effect was not due to tissue detachment or to induced cell death. In summary, the novel technology promises to open a new avenue for analyzing regulatory interactions of neuronal activity, cell differentiation and gene expression during development and in diseases. PMID:12738008

  14. Responses of rat hippocampal slices in a high-K+ medium following in vivo global ischaemia.

    PubMed

    el-Sabban, F; Reid, K H; Edmonds, H L

    1998-01-01

    1. We hypothesized that burst activity induced in rat hippocampal tissue by a high-K+ medium in vitro would be increased by a previous episode of global ischaemia, severe enough to induce persistent neurological dysfunction. 2. Male Wistar rats that were subjected to 9 min of chest compression, sufficient to reduce blood pressure (BP) to zero, showed evidence of neurological damage attributed to a global ischaemic insult. Hindlimb function was impaired for 24-48 h and a susceptibility to sound-induced seizures was induced in 25 to 35 rats. The seizure susceptibility cleared spontaneously within 2 weeks in 10 of 25 rats. 3. Hippocampal slices from postischaemic rats were prepared, tested for viability and were then exposed to an 8.0 mmol/L K+ artificial cerebrospinal fluid in vitro. Spontaneous epileptiform bursting activity in the high-K+ medium was not increased. Instead, burst size decreased with time after ischaemia. 4. The decrement in bursting activity is attributed to loss of cellular activity or integrity. These changes correlate with functional changes described by others, but not necessarily to histologically verifiable cell death. The time course of these changes was remarkably long, continuing for almost 3 weeks. Thus, a less-than-lethal ischaemia appears to induce neuronal changes, possibly reversible, that continue for at least 20 days after the global ischaemic insult. PMID:9673437

  15. Neuroprotective effects of okadaic acid following oxidative injury in organotypic hippocampal slice culture.

    PubMed

    Kim, Un Jeng; Won, Ran; Lee, Kyung Hee

    2015-08-27

    Oxidative stress produces neurotoxicity often related with various CNS disorders. A phosphatase inhibitor enhances the actions of the signaling kinases. Protein kinases mediated-action shows the neural protection in brain injury. Phosphatase inhibitor, okadaic acid (OA), may enhance the protection effect and benefit to improve neuronal plasticity in post-injury. Thus, we investigated that the protein prophatase inhibitor affects neuroprotective signaling and neuroplastic changes in hippocampus after oxidative injury. Electrophysiological and biochemical assays were used to observe changes in synaptic efficacy following electrical and/or pharmacological manipulation of synaptic function. Neuronal cell death, as assessed by propidium iodide (PI) uptake, was reduced by OA treatment (24 and 48 h) compared with KA treatment. The pattern of DCFH-DA fluorescence in hippocampal slices corresponded well with PI uptake. The phospho-AKT/AKT ratio showed that the level of phospho-AKT was significantly increased in the OA-treated group. Furthermore, the OA-treated group exhibited significantly increased expression of SOD2 compared with the KA-only group. Optical imaging revealed that KA treatment tended to delay the latency of electrical stimulation and decrease the amplitude of optical signals of synaptic activity. These results suggest that OA may protect hippocampal neurons against oxidative stress and the survived neurons may functional to synaptic plasticity changes. PMID:26067888

  16. Sevoflurane improves electrophysiological recovery of rat hippocampal slice CA1 pyramidal neurons after hypoxia.

    PubMed

    Matei, Gina; Pavlik, Rostislav; McCadden, Tai; Cottrell, James E; Kass, Ira S

    2002-10-01

    Sevoflurane is a volatile anesthetic agent that reduces cerebral metabolism and thereby may reduce neuronal damage during energy deprivation. We have examined the effect of sevoflurane on hypoxic neuronal damage in rat hippocampal slices. Slices were subjected to 0%, 2%, or 4% sevoflurane 10 minutes before, during, and 10 minutes after hypoxia. The Schaffer collateral pathway was stimulated every 10 seconds and the evoked population spike recorded in the CA1 pyramidal cell region throughout the experiment. During hypoxia, the postsynaptic evoked response was blocked. The time until the blockade of this response in the 0% sevoflurane group was 158 seconds. Sevoflurane (4%) significantly delayed the loss of the evoked response during hypoxia (242 seconds). The percent recovery of the postsynaptic population spike was calculated by dividing the size of the response 120 minutes after hypoxia by its prehypoxic, presevoflurane amplitude. There was no recovery of the population spike in the 0% sevoflurane group 120 minutes after the end of 5 minutes of hypoxia (6 +/- 6%); there was significantly better recovery after 5 minutes of hypoxia in the sevoflurane (4%) treated group (40 +/- 9%). A lower concentration of sevoflurane (2%) delayed the loss of evoked response during hypoxia (191 seconds), but it did not significantly affect recovery of the population spike after hypoxia (7 +/- 7%). Hypoxia irreversibly damages electrophysiologic activity. A high, but clinically usable, concentration of sevoflurane increases the time during hypoxia until the postsynaptic evoked response is blocked and improves recovery of this response after 5 minutes of hypoxia. PMID:12357086

  17. Identification and two-photon imaging of oligodendrocyte in CA1 region of hippocampal slices

    SciTech Connect

    Zhou Wei; Ge Wooping; Zeng Shaoqun; Duan Shumin; Luo Qingming . E-mail: qluo@mail.hust.edu.cn

    2007-01-19

    Oligodendrocyte (OL) plays a critical role in myelination and axon maintenance in central nervous system. Recent studies show that OL can also express NMDA receptors in development and pathological situations in white matter. There is still lack of studies about OL properties and function in gray matter of brain. Here we reported that some glial cells in CA1 region of rat hippocampal slices (P15-23) had distinct electrophysiological characteristics from the other glia cells in this region, while they displayed uniform properties with OL from white matter in previous report; therefore, they were considered as OL in hippocampus. By loading dye in recording pipette and imaging with two-photon laser scanning microscopy, we acquired the high spatial resolution, three-dimension images of these special cells in live slices. The OL in hippocampus shows a complex process-bearing shape and the distribution of several processes is parallel to Schaffer fiber in CA1 region. When stimulating Schaffer fiber, OL displays a long duration depolarization mediated by inward rectifier potassium channel. This suggested that the OL in CA1 region could sense the neuronal activity and contribute to potassium clearance.

  18. Post-embedding Immunogold Labeling of Synaptic Proteins in Hippocampal Slice Cultures

    PubMed Central

    Zhong, Ling; Brown, Joshua C.; Wells, Clive; Gerges, Nashaat Z.

    2013-01-01

    in brain and spinal cord tissues7. We have adopted this osmium-free post-embedding method to rat brain tissue and optimized the immunogold labeling technique to detect and study synaptic proteins. We present here a method to determine the ultrastructural localization of synaptic proteins in rat hippocampal CA1 pyramidal neurons. We use organotypic hippocampal cultured slices. These slices maintain the trisynaptic circuitry of the hippocampus, and thus are especially useful for studying synaptic plasticity, a mechanism widely thought to underlie learning and memory. Organotypic hippocampal slices from postnatal day 5 and 6 mouse/rat pups can be prepared as described previously8, and are especially useful to acutely knockdown or overexpress exogenous proteins. We have previously used this protocol to characterize neurogranin (Ng), a neuron-specific protein with a critical role in regulating synaptic function8,9 . We have also used it to characterize the ultrastructural localization of calmodulin (CaM) and Ca2+/CaM-dependent protein kinase II (CaMKII)10. As illustrated in the results, this protocol allows good ultrastructural preservation of dendritic spines and efficient labeling of Ng to help characterize its distribution in the spine8. Furthermore, the procedure described here can have wide applicability in studying many other proteins involved in neuronal functions. PMID:23609099

  19. Isolated primary blast alters neuronal function with minimal cell death in organotypic hippocampal slice cultures.

    PubMed

    Effgen, Gwen B; Vogel, Edward W; Lynch, Kimberly A; Lobel, Ayelet; Hue, Christopher D; Meaney, David F; Bass, Cameron R Dale; Morrison, Barclay

    2014-07-01

    An increasing number of U.S. soldiers are diagnosed with traumatic brain injury (TBI) subsequent to exposure to blast. In the field, blast injury biomechanics are highly complex and multi-phasic. The pathobiology caused by exposure to some of these phases in isolation, such as penetrating or inertially driven injuries, has been investigated extensively. However, it is unclear whether the primary component of blast, a shock wave, is capable of causing pathology on its own. Previous in vivo studies in the rodent and pig have demonstrated that it is difficult to deliver a primary blast (i.e., shock wave only) without rapid head accelerations and potentially confounding effects of inertially driven TBI. We have previously developed a well-characterized shock tube and custom in vitro receiver for exposing organotypic hippocampal slice cultures to pure primary blast. In this study, isolated primary blast induced minimal hippocampal cell death (on average, below 14% in any region of interest), even for the most severe blasts tested (424 kPa peak pressure, 2.3 ms overpressure duration, and 248 kPa*ms impulse). In contrast, measures of neuronal function were significantly altered at much lower exposures (336 kPa, 0.84 ms, and 86.5 kPa*ms), indicating that functional changes occur at exposures below the threshold for cell death. This is the first study to investigate a tolerance for primary blast-induced brain cell death in response to a range of blast parameters and demonstrate functional deficits at subthreshold exposures for cell death. PMID:24558968

  20. Administration of copper reduced the hyper-excitability of neurons in CA1 hippocampal slices from epileptic rats.

    PubMed

    Leiva, Juan; Infante, Claudio

    2016-04-01

    Copper as a trace metal is involved in several neurodegenerative illnesses, such as Menkes, Wilson's, Alzheimer's, amyotrophic lateral sclerosis (ALS), and Creutzfeldt-Jakob. Electrophysiological evidence indicates that acute perfusion of copper can inhibit long-term synaptic potentiation in hippocampal slices. The objective of this work is to determine whether Cu perfusion can perturb synaptic transmission in hippocampal slices derived from pilocarpine treated epileptic rats. Field potential (FP) recordings of the CA1 neurons of rats with chronic epilepsy showed voltage and response duration decrease following copper sulfate perfusion. However, voltage and response duration were higher after removing copper by washing. The discharge frequency of the CA1 neurons of hippocampal slices from non-epileptic control rats was increased after acute perfusion of 10 μM of pilocarpine. This increase was blocked by administering copper sulphate 10 μM. Krebs-Ringer solution washing re-established the discharges, with a higher frequency than that provoked by pilocarpine perfusion. We discuss the blocking effect of copper and the synaptic hyper-excitability generated by its removal. PMID:27548095

  1. The amiloride-sensitive Na+/H+ exchange antiporter and control of intracellular pH in hippocampal brain slices.

    PubMed

    Lin, C W; Kalaria, R N; Kroon, S N; Bae, J Y; Sayre, L M; LaManna, J C

    1996-08-26

    The intracellular pH, 7.54 +/- 0.03 (mean +/- S.D., n = 15), determined with the Neutral red method, of the hippocampal brain slice preparation under baseline incubation conditions is considerably more alkaline than the bath buffer pH. Neutralization by amiloride suggests that the alkalinity was due to Na+/H+ exchange antiporter activation. To characterize the brain Na+/H+ exchange antiporter we compared the inhibitory effects of MIA, amiloride and other 5-N substituted analogues on proton extrusion after acid loading by transient exposure to ammonium chloride in the isolated hippocampal brain slice preparation. The potencies of amiloride compounds on the initial recovery rate of intracellular pH after acid-loading were DMA > MIA > HMA = MHA > or = IPA-HCI > IPA > MNPA = Amil > Benzamil. The greater potency of the 5-N substituted analogs of amiloride over amiloride and benzamil strongly suggest that Na+/H+ exchange antiporter is the mechanism responsible for alkalinization in the isolated hippocampal brain slice in vitro. PMID:8883860

  2. Guanosine controls inflammatory pathways to afford neuroprotection of hippocampal slices under oxygen and glucose deprivation conditions.

    PubMed

    Dal-Cim, Tharine; Ludka, Fabiana K; Martins, Wagner C; Reginato, Charlise; Parada, Esther; Egea, Javier; López, Manuela G; Tasca, Carla I

    2013-08-01

    Guanosine (GUO) is an endogenous modulator of glutamatergic excitotoxicity and has been shown to promote neuroprotection in in vivo and in vitro models of neurotoxicity. This study was designed to understand the neuroprotective mechanism of GUO against oxidative damage promoted by oxygen/glucose deprivation and reoxygenation (OGD). GUO (100 μM) reduced reactive oxygen species production and prevented mitochondrial membrane depolarization induced by OGD. GUO also exhibited anti-inflammatory actions as inhibition of nuclear factor kappa B activation and reduction of inducible nitric oxide synthase induction induced by OGD. These GUO neuroprotective effects were mediated by adenosine A1 receptor, phosphatidylinositol-3 kinase and MAPK/ERK. Furthermore, GUO recovered the impairment of glutamate uptake caused by OGD, an effect that occurred via a Pertussis toxin-sensitive G-protein-coupled signaling, blockade of adenosine A2A receptors (A2A R), but not via A1 receptor. The modulation of glutamate uptake by GUO also involved MAPK/ERK activation. In conclusion, GUO, by modulating adenosine receptor function and activating MAPK/ERK, affords neuroprotection of hippocampal slices subjected to OGD by a mechanism that implicates the following: (i) prevention of mitochondrial membrane depolarization, (ii) reduction of oxidative stress, (iii) regulation of inflammation by inhibition of nuclear factor kappa B and inducible nitric oxide synthase, and (iv) promoting glutamate uptake. PMID:23713463

  3. Glycolysis and oxidative phosphorylation in neurons and astrocytes during network activity in hippocampal slices

    PubMed Central

    Ivanov, Anton I; Malkov, Anton E; Waseem, Tatsiana; Mukhtarov, Marat; Buldakova, Svetlana; Gubkina, Olena; Zilberter, Misha; Zilberter, Yuri

    2014-01-01

    Network activation triggers a significant energy metabolism increase in both neurons and astrocytes. Questions of the primary neuronal energy substrate (e.g., glucose vs. lactate) as well as the relative contributions of glycolysis and oxidative phosphorylation and their cellular origin (neurons vs. astrocytes) are still a matter of debates. Using simultaneous measurements of electrophysiological and metabolic parameters during synaptic stimulation in hippocampal slices from mature mice, we show that neurons and astrocytes use both glycolysis and oxidative phosphorylation to meet their energy demands. Supplementation or replacement of glucose in artificial cerebrospinal fluid (ACSF) with pyruvate or lactate strongly modifies parameters related to network activity-triggered energy metabolism. These effects are not induced by changes in ATP content, pHi, [Ca2+]i or accumulation of reactive oxygen species. Our results suggest that during network activation, a significant fraction of NAD(P)H response (its overshoot phase) corresponds to glycolysis and the changes in cytosolic NAD(P)H and mitochondrial FAD are coupled. Our data do not support the hypothesis of a preferential utilization of astrocyte-released lactate by neurons during network activation in slices—instead, we show that during such activity glucose is an effective energy substrate for both neurons and astrocytes. PMID:24326389

  4. Synaptic plasticity in area CA1 of rat hippocampal slices following intraventricular application of albumin.

    PubMed

    Salar, Seda; Lapilover, Ezequiel; Müller, Julia; Hollnagel, Jan-Oliver; Lippmann, Kristina; Friedman, Alon; Heinemann, Uwe

    2016-07-01

    Epileptogenesis following insults to the brain may be triggered by a dysfunctional blood-brain barrier (BBB) associated with albumin extravasation and activation of astrocytes. Using ex vivo recordings from the BBB-disrupted hippocampus after neocortical photothrombotic stroke, we previously demonstrated abnormal activity-dependent accumulation of extracellular potassium with facilitated generation of seizure like events and spreading depolarizations. Similar changes could be observed after intracerebroventricular (icv) application of albumin. We hypothesized that alterations in extracellular potassium and glutamate homeostasis might lead to alterations in synaptic interactions. We therefore assessed the effects of icv albumin on homo- and heterosynaptic plasticity in hippocampal CA1, 24h after a single injection or 7days after continuous infusion of icv albumin. We demonstrate alterations in both homo- and heterosynaptic plasticity compared to control conditions in ex vivo slice studies. Albumin-treated tissue reveals (1) reduced long-term depression following low-frequency stimulation; (2) increased long-term potentiation of population spikes in response to 20Hz stimulation; (3) potentiated responses to Schaffer collateral stimulation following high-frequency stimulation of the direct cortical input and low-frequency stimulation of alveus and finally, (4) TGFβ receptor II (TGFβR-II) involvement in albumin-induced homosynaptic plasticity changes. We conclude that albumin-induced network hyperexcitability is associated with abnormal homo- and heterosynaptic plasticity that could partly be reversed by interference with TGFβR-II-mediated signaling and therefore it might be an important factor in the process of epileptogenesis. PMID:26972679

  5. Involvement of cellular metabolism in age-related LTP modifications in rat hippocampal slices

    PubMed Central

    Drulis-Fajdasz, Dominika; Wójtowicz, Tomasz; Wawrzyniak, Marcin; Wlodarczyk, Jakub; Mozrzymas, Jerzy W.; Rakus, Dariusz

    2015-01-01

    Recent studies emphasized crucial role of astrocytic glycogen metabolism in regulation of synaptic transmission and plasticity in young animals. However, the interplay between age-related synaptic plasticity impairments and changes in energetic metabolism remains obscure. To address this issue, we investigated, in hippocampal slices of young (one month) and aged rats (20-22-months), the impact of glycogen degradation inhibition on LTP, mRNA expression for glycogen metabolism enzymes and morphology of dendritic spines. We show that, whereas in young hippocampi, inhibition of glycogen phosphorolysis disrupts the late phase of LTP in the Schaffer collateral-CA1 pathway, in aged rats, blockade of glycogen phosphorylase tends to enhance it. Gene expression for key energy metabolism enzymes, such as glycogen synthase and phosphorylase and glutamine synthetase showed marked differences between young and aged groups and changes in expression of these enzymes preceded plasticity phenomena. Interestingly, in the aged group, a prominent expression of these enzymes was found also in neurons. Concluding, we show that LTP in the considered pathway is differentially modulated by metabolic processes in young and aging animals, indicating a novel venue of studies aiming at preventing cognitive decline during aging. PMID:26101857

  6. Effects of selected muscarinic cholinergic antagonists on [3H]acetylcholine release from rat hippocampal slices.

    PubMed

    Pohorecki, R; Head, R; Domino, E F

    1988-01-01

    A number of cholinergic muscarinic (M) agonists and antagonists were studied for their ability to enhance tritiated acetylcholine ([3H]ACh) release from electrically field-stimulated rat hippocampal slices. A Ca++-free medium and carbachol, but not nicotine, inhibited [3H]ACh release. Atropine, methylatropine and dexetimide produced concentration-dependent increases in [3H]ACh release to a maximum of about 50% above control. Aprophen and benactyzine produced a maximal response 25 to 35% above control. The selective M1 antagonist pirenzepine had the least effect on [3H]ACh release. Of the nonspecific M1-M2 antagonists studied, benactyzine produced the least amount of [3H]ACh release. The order of potency of the M antagonists in promoting a 15% increase in [3H]ACh release was aprophen greater than benactyzine greater than methylatropine greater than dexetimide greater than pirenzepine greater than atropine. However, the order of promoting maximal release of [3H]ACh was atropine greater than dexetimide greater than methylatropine greater than aprophen greater than benactyzine greater than pirenzepine. PMID:3335998

  7. Isolated Primary Blast Inhibits Long-Term Potentiation in Organotypic Hippocampal Slice Cultures.

    PubMed

    Vogel, Edward W; Effgen, Gwen B; Patel, Tapan P; Meaney, David F; Bass, Cameron R Dale; Morrison, Barclay

    2016-04-01

    Over the last 13 years, traumatic brain injury (TBI) has affected over 230,000 U.S. service members through the conflicts in Iraq and Afghanistan, mostly as a result of exposure to blast events. Blast-induced TBI (bTBI) is multi-phasic, with the penetrating and inertia-driven phases having been extensively studied. The effects of primary blast injury, caused by the shockwave interacting with the brain, remain unclear. Earlier in vivo studies in mice and rats have reported mixed results for primary blast effects on behavior and memory. Using a previously developed shock tube and in vitro sample receiver, we investigated the effect of isolated primary blast on the electrophysiological function of rat organotypic hippocampal slice cultures (OHSC). We found that pure primary blast exposure inhibited long-term potentiation (LTP), the electrophysiological correlate of memory, with a threshold between 9 and 39 kPa·ms impulse. This deficit occurred well below a previously identified threshold for cell death (184 kPa·ms), supporting our previously published finding that primary blast can cause changes in brain function in the absence of cell death. Other functional measures such as spontaneous activity, network synchronization, stimulus-response curves, and paired-pulse ratios (PPRs) were less affected by primary blast exposure, as compared with LTP. This is the first study to identify a tissue-level tolerance threshold for electrophysiological changes in neuronal function to isolated primary blast. PMID:26414012

  8. Effects of uniform extracellular DC electric fields on excitability in rat hippocampal slices in vitro

    PubMed Central

    Bikson, Marom; Inoue, Masashi; Akiyama, Hiroki; Deans, Jackie K; Fox, John E; Miyakawa, Hiroyoshi; Jefferys, John G R

    2004-01-01

    The effects of uniform steady state (DC) extracellular electric fields on neuronal excitability were characterized in rat hippocampal slices using field, intracellular and voltage-sensitive dye recordings. Small electric fields (<|40| mV mm−1), applied parallel to the somato-dendritic axis, induced polarization of CA1 pyramidal cells; the relationship between applied field and induced polarization was linear (0.12 ± 0.05 mV per mV mm−1 average sensitivity at the soma). The peak amplitude and time constant (15–70 ms) of membrane polarization varied along the axis of neurons with the maximal polarization observed at the tips of basal and apical dendrites. The polarization was biphasic in the mid-apical dendrites; there was a time-dependent shift in the polarity reversal site. DC fields altered the thresholds of action potentials evoked by orthodromic stimulation, and shifted their initiation site along the apical dendrites. Large electric fields could trigger neuronal firing and epileptiform activity, and induce long-term (>1 s) changes in neuronal excitability. Electric fields perpendicular to the apical–dendritic axis did not induce somatic polarization, but did modulate orthodromic responses, indicating an effect on afferents. These results demonstrate that DC fields can modulate neuronal excitability in a time-dependent manner, with no clear threshold, as a result of interactions between neuronal compartments, the non-linear properties of the cell membrane, and effects on afferents. PMID:14978199

  9. Short-term environmental enrichment enhances synaptic plasticity in hippocampal slices from aged rats.

    PubMed

    Stein, Liana R; O'Dell, Kazuko A; Funatsu, Michiyo; Zorumski, Charles F; Izumi, Yukitoshi

    2016-08-01

    Age-associated changes in cognition are mirrored by impairments in cellular models of memory and learning, such as long-term potentiation (LTP) and long-term depression (LTD). In young rodents, environmental enrichment (EE) can enhance memory, alter LTP and LTD, as well as reverse cognitive deficits induced by aging. Whether short-term EE can benefit cognition and synaptic plasticity in aged rodents is unclear. Here, we tested if short-term EE could overcome age-associated impairments in induction of LTP and LTD. LTP and LTD could not be induced in the CA1 region of hippocampal slices in control, aged rats using standard stimuli that are highly effective in young rats. However, exposure of aged littermates to EE for three weeks enabled successful induction of LTP and LTD. EE-facilitated LTP was dependent upon N-methyl-d-aspartate receptors (NMDARs). These alterations in synaptic plasticity occurred with elevated levels of phosphorylated cAMP response element-binding protein and vascular endothelial growth factor, but in the absence of changes in several other synaptic and cellular markers. Importantly, our study suggests that even a relatively short period of EE is sufficient to alter synaptic plasticity and molecular markers linked to cognitive function in aged animals. PMID:27208617

  10. Dual Electrophysiological Recordings of Synaptically-evoked Astroglial and Neuronal Responses in Acute Hippocampal Slices

    PubMed Central

    Rouach, Nathalie

    2012-01-01

    Astrocytes form together with neurons tripartite synapses, where they integrate and modulate neuronal activity. Indeed, astrocytes sense neuronal inputs through activation of their ion channels and neurotransmitter receptors, and process information in part through activity-dependent release of gliotransmitters. Furthermore, astrocytes constitute the main uptake system for glutamate, contribute to potassium spatial buffering, as well as to GABA clearance. These cells therefore constantly monitor synaptic activity, and are thereby sensitive indicators for alterations in synaptically-released glutamate, GABA and extracellular potassium levels. Additionally, alterations in astroglial uptake activity or buffering capacity can have severe effects on neuronal functions, and might be overlooked when characterizing physiopathological situations or knockout mice. Dual recording of neuronal and astroglial activities is therefore an important method to study alterations in synaptic strength associated to concomitant changes in astroglial uptake and buffering capacities. Here we describe how to prepare hippocampal slices, how to identify stratum radiatum astrocytes, and how to record simultaneously neuronal and astroglial electrophysiological responses. Furthermore, we describe how to isolate pharmacologically the synaptically-evoked astroglial currents. PMID:23222635

  11. Differential distribution of release-related proteins in the hippocampal CA3 area as revealed by freeze-fracture replica labeling.

    PubMed

    Hagiwara, Akari; Fukazawa, Yugo; Deguchi-Tawarada, Maki; Ohtsuka, Toshihisa; Shigemoto, Ryuichi

    2005-08-22

    Synaptic vesicle release occurs at a specialized membrane domain known as the presynaptic active zone (AZ). Several membrane proteins are involved in the vesicle release processes such as docking, priming, and exocytotic fusion. Cytomatrix at the active zone (CAZ) proteins are structural components of the AZ and are highly concentrated in it. Localization of other release-related proteins including target soluble N-ethylmaleimide-sensitive-factor attachment protein receptor (t-SNARE) proteins, however, has not been well demonstrated in the AZ. Here, we used sodium dodecyl sulfate-digested freeze-fracture replica labeling (SDS-FRL) to analyze quantitatively the distribution of CAZ and t-SNARE proteins in the hippocampal CA3 area. The AZ in replicated membrane was identified by immunolabeling for CAZ proteins (CAZ-associated structural protein [CAST] and Bassoon). Clusters of immunogold particles for these proteins were found on the P-face of presynaptic terminals of the mossy fiber and associational/commissural (A/C) fiber. Co-labeling with CAST revealed distribution of the t-SNARE proteins syntaxin and synaptosomal-associated protein of 25 kDa (SNAP-25) in the AZ as well as in the extrasynaptic membrane surrounding the AZ (SZ). Quantitative analysis demonstrated that the density of immunoparticles for CAST in the AZ was more than 100 times higher than in the SZ, whereas that for syntaxin and SNAP-25 was not significantly different between the AZ and SZ in both the A/C and mossy fiber terminals. These results support the involvement of the t-SNARE proteins in exocytotic fusion in the AZ and the role of CAST in specialization of the membrane domain for the AZ. PMID:15983999

  12. Kainic acid-induced neurodegeneration and activation of inflammatory processes in organotypic hippocampal slice cultures: treatment with cyclooxygenase-2 inhibitor does not prevent neuronal death.

    PubMed

    Järvelä, Juha T; Ruohonen, Saku; Kukko-Lukjanov, Tiina-Kaisa; Plysjuk, Anna; Lopez-Picon, Francisco R; Holopainen, Irma E

    2011-06-01

    In the postnatal rodent hippocampus status epilepticus (SE) leads to age- and region-specific excitotoxic neuronal damage, the precise mechanisms of which are still incompletely known. Recent studies suggest that the activation of inflammatory responses together with glial cell reactivity highly contribute to excitotoxic neuronal damage. However, pharmacological tools to attenuate their activation in the postnatal brain are still poorly elucidated. In this study, we investigated the role of inflammatory mediators in kainic acid (KA)-induced neuronal damage in organotypic hippocampal slice cultures (OHCs). A specific cyclooxygenase-2 (COX-2) inhibitor N-[2-(cyclohexyloxy)-4-nitrophenyl]-methanesulfonamide (NS-398) was used to study whether or not it could ameliorate neuronal death. Our results show that KA treatment (24 h) resulted in a dose-dependent degeneration of CA3a/b pyramidal neurons. Furthermore, COX-2 immunoreactivity was pronouncedly enhanced particularly in CA3c pyramidal neurons, microglial and astrocyte morphology changed from a resting to active appearance, the expression of the microglial specific protein, Iba1, increased, and prostaglandin E₂ (PGE₂) production increased. These indicated the activation of inflammatory processes. However, the expression of neither proinflammatory cytokines, i.e. tumour necrosis factor-alpha (TNF-α) and interleukin-1 beta (IL-1β), nor the anti-inflammatory cytokine IL-10 mRNA was significantly altered by KA treatment as studied by real-time PCR. Despite activation of an array of inflammatory processes, neuronal damage could not be rescued either with the combined pre- and co-treatment with a specific COX-2 inhibitor, NS-398. Our results suggest that KA induces activation of a repertoire of inflammatory processes in immature OHCs, and that the timing of anti-inflammatory treatment to achieve neuroprotection is a challenge due to developmental properties and the complexity of inflammatory processes activated by

  13. Effect of short-term exposure to dichlorvos on synaptic plasticity of rat hippocampal slices: Involvement of acylpeptide hydrolase and {alpha}{sub 7} nicotinic receptors

    SciTech Connect

    Olmos, Cristina; Sandoval, Rodrigo; Rozas, Carlos; Navarro, Sebastian; Wyneken, Ursula; Zeise, Marc; Morales, Bernardo; Pancetti, Floria

    2009-07-01

    Dichlorvos is the active molecule of the pro-drug metrifonate used to revert the cognitive deficits associated with Alzheimer's disease. A few years ago it was reported that dichlorvos inhibits the enzyme acylpeptide hydrolase at lower doses than those necessary to inhibit acetylcholinesterase to the same extent. Therefore, the aim of our investigation was to test the hypothesis that dichlorvos can enhance synaptic efficacy through a mechanism that involves acylpeptide hydrolase instead of acetylcholinesterase inhibition. We used long-term potentiation induced in rat hippocampal slices as a model of synaptic plasticity. Our results indicate that short-term exposures (20 min) to 50 {mu}M dichlorvos enhance long-term potentiation in about 200% compared to the control condition. This effect is correlated with approximately 60% inhibition of acylpeptide hydrolase activity, whereas acetylcholinesterase activity remains unaffected. Paired-pulse facilitation and inhibition experiments indicate that dichlorvos does not have any presynaptic effect in the CA3 {yields} CA1 pathway nor affect gabaergic interneurons. Interestingly, the application of 100 nM methyllicaconitine, an {alpha}{sub 7} nicotinic receptor antagonist, blocked the enhancing effect of dichlorvos on long-term potentiation. These results indicate that under the exposure conditions described above, dichlorvos enhances long-term potentiation through a postsynaptic mechanism that involves (a) the inhibition of the enzyme acylpeptide hydrolase and (b) the modulation of {alpha}{sub 7} nicotinic receptors.

  14. Conditions sufficient for nonsynaptic epileptogenesis in the CA1 region of hippocampal slices.

    PubMed

    Bikson, Marom; Baraban, Scott C; Durand, Dominique M

    2002-01-01

    Nonsynaptic mechanisms exert a powerful influence on seizure threshold. It is well-established that nonsynaptic epileptiform activity can be induced in hippocampal slices by reducing extracellular Ca(2+) concentration. We show here that nonsynaptic epileptiform activity can be readily induced in vitro in normal (2 mM) Ca(2+) levels. Those conditions sufficient for nonsynaptic epileptogenesis in the CA1 region were determined by pharmacologically mimicking the effects of Ca(2+) reduction in normal Ca(2+) levels. Increasing neuronal excitability, by removing extracellular Mg(2+) and increasing extracellular K(+) (6-15 mM), induced epileptiform activity that was suppressed by postsynaptic receptor antagonists [D-(-)-2-amino-5-phosphonopentanoic acid, picrotoxin, and 6,7-dinitroquinoxaline-2,3-dione] and was therefore synaptic in nature. Similarly, epileptiform activity induced when neuronal excitability was increased in the presence of K(Ca) antagonists (verruculogen, charybdotoxin, norepinephrine, tetraethylammonium salt, and Ba(2+)) was found to be synaptic in nature. Decreases in osmolarity also failed to induce nonsynaptic epileptiform activity in the CA1 region. However, increasing neuronal excitability (by removing extracellular Mg(2+) and increasing extracellular K(+)) in the presence of Cd(2+), a nonselective Ca(2+) channel antagonist, or veratridine, a persistent sodium conductance enhancer, induced spontaneous nonsynaptic epileptiform activity in vitro. Both novel models were characterized using intracellular and ion-selective electrodes. The results of this study suggest that reducing extracellular Ca(2+) facilitates bursting by increasing neuronal excitability and inhibiting Ca(2+) influx, which might, in turn, enhance a persistent sodium conductance. Furthermore, these data show that nonsynaptic mechanisms can contribute to epileptiform activity in normal Ca(2+) levels. PMID:11784730

  15. Interstitial space, electrical resistance and ion concentrations during hypotonia of rat hippocampal slices.

    PubMed Central

    Chebabo, S R; Hester, M A; Jing, J; Aitken, P G; Somjen, G G

    1995-01-01

    1. The degree to which mammalian brain cells swell in hypotonic environments has not previously been determined. We exposed hippocampal tissue slices prepared from anaesthetized rats to artificial cerebrospinal fluid from which varying amounts of NaCl had been deleted. Interstitial volume (ISV) change was determined from the volume of dilution of the marker ions tetramethylammonium (TMA+) or tetraethylammonium (TEA+). Tissue electrical resistance was measured as the voltage generated by constant current pulses. 2. ISV decreased as a function of lowered extracellular osmolality (osmotic pressure, pi o), indicating cell swelling. After reaching a minimum, ISV recovered partially, suggesting regulatory volume decrease of cells. After restoring normal pi o the ISV expanded, indicating post-hypotonic cell shrinkage. The electrical resistance of the tissue (Ro) increased when pi o was lowered, due to the reduced ionic strength, as well as restricted ISV. 3. To control for low NaCl concentration, reduced NaCl was replaced by mannitol or fructose. In isosmotic, NaCl-deficient solution, ISV showed inconsistent change, and Ro corrected for ionic strength tended to decrease. 4. Extracellular K+ concentration decreased slightly in low pi o except when spreading depression caused it to increase. Extracellular Ca2+ concentration decreased substantially, consistently and reversibly. Administration of isosmotic low-NaCl concentration solutions caused a similar decrease in extracellular Ca2+ concentrations. We propose that low Na+ concentration in extracellular fluid impaired the extrusion of Ca2+. 5. In severely hypotonic solution, ISV was reduced to 25% of its control volume, corresponding to a mean cell volume increase of at least 11%, probably more. From plotting relative changes in ISV against osmolarity we concluded that, within the range tested, hypotonic cell swelling was not opposed by the close approach of plasma membranes of neighbouring cells. PMID:8544131

  16. N-Methyl-d-aspartate (NMDA) Receptor NR2 Subunit Selectivity of a Series of Novel Piperazine-2,3-dicarboxylate Derivatives: Preferential Blockade of Extrasynaptic NMDA Receptors in the Rat Hippocampal CA3-CA1 Synapse

    PubMed Central

    Feng, Bihua; Tsintsadze, Timur S.; Morley, Richard M.; Irvine, Mark W.; Tsintsadze, Vera; Lozovaya, Natasha A.; Jane, David E.; Monaghan, Daniel T.

    2009-01-01

    -mediated CA3-CA1 synaptic response in rat hippocampal slices. UBP125, UBP128, UBP141, and UBP145 may be useful tools for determining the function of NMDA receptor subtypes. PMID:19684252

  17. Low-frequency electrical stimulation enhances the effectiveness of phenobarbital on GABAergic currents in hippocampal slices of kindled rats.

    PubMed

    Asgari, Azam; Semnanian, Saeed; Atapour, Nafiseh; Shojaei, Amir; Moradi-Chameh, Homeira; Ghafouri, Samireh; Sheibani, Vahid; Mirnajafi-Zadeh, Javad

    2016-08-25

    Low frequency stimulation (LFS) has been proposed as a new approach in the treatment of epilepsy. The anticonvulsant mechanism of LFS may be through its effect on GABAA receptors, which are the main target of phenobarbital anticonvulsant action. We supposed that co-application of LFS and phenobarbital may increase the efficacy of phenobarbital. Therefore, the interaction of LFS and phenobarbital on GABAergic inhibitory post-synaptic currents (IPSCs) in kindled and control rats was investigated. Animals were kindled by electrical stimulation of basolateral amygdala in a semi rapid manner (12 stimulations/day). The effect of phenobarbital, LFS and phenobarbital+LFS was investigated on GABAA-mediated evoked and miniature IPSCs in the hippocampal brain slices in control and fully kindled animals. Phenobarbital and LFS had positive interaction on GABAergic currents. In vitro co-application of an ineffective pattern of LFS (100 pulses at afterdischarge threshold intensity) and a sub-threshold dose of phenobarbital (100μM) which had no significant effect on GABAergic currents alone, increased the amplitude and area under curve of GABAergic currents in CA1 pyramidal neurons of hippocampal slices significantly. Interestingly, the sub-threshold dose of phenobarbital potentiated the GABAergic currents when applied on the hippocampal slices of kindled animals which received LFS in vivo. Post-synaptic mechanisms may be involved in observed interactions. Obtained results implied a positive interaction between LFS and phenobarbital through GABAA currents. It may be suggested that a combined therapy of phenobarbital and LFS may be a useful manner for reinforcing the anticonvulsant action of phenobarbital. PMID:27235746

  18. Chronic 17β-estradiol or cholesterol prevents stress-induced hippocampal CA3 dendritic retraction in ovariectomized female rats: Possible correspondence between CA1 spine properties and spatial acquisition

    PubMed Central

    McLaughlin, Katie J.; Wilson, Jessica O.; Harman, James; Wright, Ryan L.; Wieczorek, Lindsay A.; Gomez, Juan; Korol, Donna L.; Conrad, Cheryl D.

    2009-01-01

    Chronic stress may have different effects on hippocampal CA3 and CA1 neuronal morphology and function depending upon hormonal status, but rarely are manipulations of stress and gonadal steroids combined. Experiment 1 investigated the effects of chronic restraint and 17β-estradiol replacement on CA3 and CA1 dendritic morphology and spatial learning in ovariectomized female Sprague-Dawley rats. Ovariectomized rats were implanted with 25% 17β-estradiol, 100% cholesterol or blank silastic capsules, and then chronically restrained (6h/d/21d) or kept in home cages. 17β-estradiol or cholesterol prevented stress-induced CA3 dendritic retraction, increased CA1 apical spine density, and altered CA1 spine shape. The combination of chronic stress and 17β-estradiol facilitated water maze acquisition compared to chronic stress + blank implants and nonstressed controls + 17β-estradiol. To further investigate the interaction between 17β-estradiol and stress on hippocampal morphology, Experiment 2 was conducted on gonadally intact, cycling female rats that were chronically restrained (6h/d/21d) and then euthanized at proestrus (high ovarian hormones) or estrus (low ovarian hormones). Cycling female rats failed to show chronic stress-induced CA3 dendritic retraction at either estrous phase. Chronic stress enhanced the ratio of CA1 basal spine heads to headless spines as found in Experiment 1. In addition, proestrous rats displayed increased CA1 spine density regardless of stress history. These results show that 17β-estradiol or cholesterol protect against chronic stress-induced CA3 dendritic retraction in females. These stress- and 17β-estradiol-induced morphological changes may provide insight into how dendritic complexity and spine properties contribute to spatial ability. PMID:19650122

  19. Ultrastructural investigation of microcalcification and the role of oxygen-glucose deprivation in cultured rat hippocampal slices.

    PubMed

    Riew, Tae-Ryong; Kim, Hong Lim; Shin, Yoo-Jin; Park, Joo-Hee; Pak, Ha-Jin; Lee, Mun-Yong

    2015-10-01

    Intracellular calcium accumulation is associated with cell death in several neuropathological disorders including brain ischemia, but the exact mechanisms of calcification need to be clarified. We used organotypic hippocampal slice culture - cultures subjected to oxygen-glucose deprivation (OGD) mimicking the in vivo situation to investigate the events underlying ectopic calcification. Alizarin red staining indicating calcium deposition was observed in the cornu ammonis (CA)1 and dentate gyrus regions in control hippocampal slices despite no specific labeling for cell death markers. Electron microscopy using the osmium/potassium dichromate method revealed scattered degenerated cells throughout the normally appearing CA1 region. They contained electron-dense precipitates within mitochondria, and electron probe microanalysis confirmed that they were calcifying mitochondria. Selective calcium deposition was noted within, but not beyond, mitochondria in these mineralized cells. They showed ultrastructural features of non-necrotic, non-apoptotic cell death and retained their compact ultrastructure, even after the majority of mitochondria were calcified. Unexpectedly, no intracellular calcification was noted in necrotic CA1 pyramidal cells after OGD, and there was no progression of calcification in OGD-lesioned slices. In addition, mineralized cells in both control and OGD-lesioned slices were closely associated with or completely engulfed by astrocytes but not microglia. These astrocytes were laden with heterogeneous cytoplasmic inclusions that appeared to be related with their phagocytic activity. These data demonstrate that microcalcification specifically associated with mitochondria might lead to a novel type of cell death and suggest that astrocytes may be involved in the phagocytosis of these mineralized cells and possibly in the regulation of ectopic calcification. PMID:26188662

  20. Selective inhibition of KCC2 leads to hyperexcitability and epileptiform discharges in hippocampal slices and in vivo.

    PubMed

    Sivakumaran, Sudhir; Cardarelli, Ross A; Maguire, Jamie; Kelley, Matt R; Silayeva, Liliya; Morrow, Danielle H; Mukherjee, Jayanta; Moore, Yvonne E; Mather, Robert J; Duggan, Mark E; Brandon, Nicholas J; Dunlop, John; Zicha, Stephen; Moss, Stephen J; Deeb, Tarek Z

    2015-05-27

    GABA(A) receptors form Cl(-) permeable channels that mediate the majority of fast synaptic inhibition in the brain. The K(+)/Cl(-) cotransporter KCC2 is the main mechanism by which neurons establish low intracellular Cl(-) levels, which is thought to enable GABAergic inhibitory control of neuronal activity. However, the widely used KCC2 inhibitor furosemide is nonselective with antiseizure efficacy in slices and in vivo, leading to a conflicting scheme of how KCC2 influences GABAergic control of neuronal synchronization. Here we used the selective KCC2 inhibitor VU0463271 [N-cyclopropyl-N-(4-methyl-2-thiazolyl)-2-[(6-phenyl-3-pyridazinyl)thio]acetamide] to investigate the influence of KCC2 function. Application of VU0463271 caused a reversible depolarizing shift in E(GABA) values and increased spiking of cultured hippocampal neurons. Application of VU0463271 to mouse hippocampal slices under low-Mg(2+) conditions induced unremitting recurrent epileptiform discharges. Finally, microinfusion of VU0463271 alone directly into the mouse dorsal hippocampus rapidly caused epileptiform discharges. Our findings indicated that KCC2 function was a critical inhibitory factor ex vivo and in vivo. PMID:26019342

  1. Platelet-activating factor attenuation of long-term potentiation in rat hippocampal slices via protein tyrosine kinase signaling.

    PubMed

    Reiner, Benjamin; Wang, Wenwei; Liu, Jianuo; Xiong, Huangui

    2016-02-26

    It is well established that HIV-1-infected mononuclear phagocytes release platelet activating factor (PAF) and elevated levels of PAF have been detected in blood and in the cerebrospinal fluid (CSF) of acquired immunodeficiency syndrome (AIDS) patients with HIV-associated neurocognitive disorders (HAND). It is our hypothesis that the elevated levels of PAF alter long-term potentiation (LTP) in the hippocampus, leading to neurocognitive dysfunction. To test this hypothesis, we studied the effects of PAF on LTP in the CA1 region of rat hippocampal slices. Our results showed incubation of hippocampal slices with PAF attenuated LTP. The PAF-mediated attenuation was blocked by ginkgolide B, a PAF receptor antagonist, suggesting PAF attenuation of LTP via PAF receptors. Application of lyso-PAF, an inactive PAF analog, had no apparent effect on LTP. Further investigation revealed an involvement of tyrosine kinase in PAF attenuation of LTP, which was demonstrated by lavendustin A (a specific protein tyrosine kinase inhibitor) blockage of PAF attenuation of LTP. As LTP is widely considered as the cellular and synaptic basis for learning and memory, the attenuation of LTP by PAF may contribute at least in part to the HAND pathogenesis. PMID:26808643

  2. Selective Inhibition of KCC2 Leads to Hyperexcitability and Epileptiform Discharges in Hippocampal Slices and In Vivo

    PubMed Central

    Sivakumaran, Sudhir; Cardarelli, Ross A.; Maguire, Jamie; Kelley, Matt R.; Silayeva, Liliya; Morrow, Danielle H.; Mukherjee, Jayanta; Moore, Yvonne E.; Mather, Robert J.; Duggan, Mark E.; Brandon, Nicholas J.; Dunlop, John; Zicha, Stephen

    2015-01-01

    GABAA receptors form Cl− permeable channels that mediate the majority of fast synaptic inhibition in the brain. The K+/Cl− cotransporter KCC2 is the main mechanism by which neurons establish low intracellular Cl− levels, which is thought to enable GABAergic inhibitory control of neuronal activity. However, the widely used KCC2 inhibitor furosemide is nonselective with antiseizure efficacy in slices and in vivo, leading to a conflicting scheme of how KCC2 influences GABAergic control of neuronal synchronization. Here we used the selective KCC2 inhibitor VU0463271 [N-cyclopropyl-N-(4-methyl-2-thiazolyl)-2-[(6-phenyl-3-pyridazinyl)thio]acetamide] to investigate the influence of KCC2 function. Application of VU0463271 caused a reversible depolarizing shift in EGABA values and increased spiking of cultured hippocampal neurons. Application of VU0463271 to mouse hippocampal slices under low-Mg2+ conditions induced unremitting recurrent epileptiform discharges. Finally, microinfusion of VU0463271 alone directly into the mouse dorsal hippocampus rapidly caused epileptiform discharges. Our findings indicated that KCC2 function was a critical inhibitory factor ex vivo and in vivo. PMID:26019342

  3. The L-type voltage-dependent calcium channel long-term potentiation is higher in the dorsal compared with the ventral associational/commissural CA3 hippocampal synapses.

    PubMed

    Moschovos, Christos; Papatheodoropoulos, Costas

    2016-05-01

    The diversification between dorsal (DH) and ventral (VH) hippocampus includes the different ability to support NMDA receptor-dependent long-term synaptic potentiation (LTP). In this study, we assessed the ability of associational/commissural connections in the CA3 hippocampal field to show NMDA receptor-independent LTP. We found that high-frequency stimulation under blockade of NMDA receptors induced greater LTP in DH (40.7±8.5%) than in VH (17.1±4.6%). The blocker of L-type voltage-dependent calcium channels (VDCC) nifedipine prevented the induction of LTP. We hypothesize that the different ability for VDCC-LTP between DH and VH might have important implications in the memory-related information processing performed by the circuits of the two hippocampal segments. PMID:26541214

  4. Spatial Memory Impairment is Associated with Intraneural Amyloid-β Immunoreactivity and Dysfunctional Arc Expression in the Hippocampal-CA3 Region of a Transgenic Mouse Model of Alzheimer's Disease.

    PubMed

    Morin, Jean-Pascal; Cerón-Solano, Giovanni; Velázquez-Campos, Giovanna; Pacheco-López, Gustavo; Bermúdez-Rattoni, Federico; Díaz-Cintra, Sofía

    2016-01-01

    Dysfunction of synaptic communication in cortical and hippocampal networks has been suggested as one of the neuropathological hallmarks of the early stages of Alzheimer's disease (AD). Also, several lines of evidence have linked disrupted levels of activity-regulated cytoskeletal associated protein (Arc), an immediate early gene product that plays a central role in synaptic plasticity, with AD "synaptopathy". The mapping of Arc expression patterns in brain networks has been extensively used as a marker of memory-relevant neuronal activity history. Here we evaluated basal and behavior-induced Arc expression in hippocampal networks of the 3xTg-AD mouse model of AD. The basal percentage of Arc-expressing cells in 10-month-old 3xTg-AD mice was higher than wild type in CA3 (4.88% versus 1.77% , respectively) but similar in CA1 (1.75% versus 2.75% ). Noteworthy, this difference was not observed at 3 months of age. Furthermore, although a Morris water maze test probe induced a steep (∼4-fold) increment in the percentage of Arc+ cells in the CA3 region of the 10-month-old wild-type group, no such increment was observed in age-matched 3xTg-AD, whereas the amount of Arc+ cells in CA1 increased in both groups. Further, we detected that CA3 neurons with amyloid-β were much more likely to express Arc protein under basal conditions. We propose that in 3xTg-AD mice, intraneuronal amyloid-β expression in CA3 could increase unspecific neuronal activation and subsequent Arc protein expression, which might impair further memory-stabilizing processes. PMID:26836189

  5. PROPYLTHIOURACIL (PTU)-INDUCED HYPOTHYROIDISM: EFFECTS ON SYNAPTIC TRANSMISSION AND LONG TERM POTENTIATION IN HIPPOCAMPAL SLICES.

    EPA Science Inventory

    Concern has been raised over endocrine effects of some classes of environmental chemicals. Severe hypothyroidism during critical periods of brain developmental leads to alterations in hippocampal structure, learning deficits, yet neurophysiological properties of the hippocampus...

  6. Changes in intrinsic inhibition in isolated hippocampal slices during ethanol withdrawal; lack of correlation with withdrawal hyperexcitability.

    PubMed Central

    Whittington, M. A.; Little, H. J.; Lambert, J. D.

    1992-01-01

    1. Intracellular recordings were made from pyramidal cells in area CA1 in mouse isolated hippocampal slices, after chronic ethanol treatment in vivo. 2. Fast i.p.s.ps were isolated by injection of the impaled neurones with QX314 (to block fast sodium currents and the slow i.p.s.p.) and stimulating the interneurones in the presence of the glutamatergic blockers, CNQX and APV. 3. The isolated fast-inhibitory postsynaptic potential (f.-i.p.s.p.) was measured at intervals during the 7 h withdrawal period. The reversal potential and sensitivity to bicuculline suggested that the isolated f.-i.p.s.p. was mediated by activation of the GABAA receptor-chloride ionophore complex. 4. Measurement of stimulus-response relationships for the f.-i.p.s.ps revealed an initial increase in the maximum size of the i.p.s.p., evoked from a membrane potential of -50 mV, seen at 2 h into ethanol withdrawal. This was attributed to a negative shift in the reversal potential, Ei.p.s.p., with no observed change in conductance, Gi.p.s.p. 5. No differences in f.-i.p.s.ps evoked during ethanol withdrawal or in control slices were seen at 4 h or 6 h. At these times, epileptiform activity was seen in previous field potential recordings. 6. Paired pulse depression of the f.-i.p.s.p. was significantly increased at 2 h into withdrawal, when a 150 ms pulse interval was used. No differences were seen at later times in the ethanol withdrawal period. 7. The results suggest that ethanol withdrawal hyperexcitability in isolated hippocampal slices is not caused by primary decreases in inhibition mediated by the GABAA receptor-chloride ionophore complex.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:1330182

  7. Effects of monomethylarsonic and monomethylarsonous acid on evoked synaptic potentials in hippocampal slices of adult and young rats

    SciTech Connect

    Krueger, Katharina Straub, Heidrun; Hirner, Alfred V.; Hippler, Joerg; Binding, Norbert; Musshoff, Ulrich

    2009-04-01

    Arsenite and its metabolites, dimethylarsinic or dimethylarsinous acid, have previously been shown to disturb synaptic transmission in hippocampal slices of rats (Krueger, K., Gruner, J., Madeja, M., Hartmann, L.M., Hirner, A.V., Binding, N., Mu{beta}hoff, U., 2006a. Blockade and enhancement of glutamate receptor responses in Xenopus oocytes by methylated arsenicals. Arch. Toxicol. 80, 492-501, Krueger, K., Straub, H., Binding, N., Mu{beta}hoff, U., 2006b. Effects of arsenite on long-term potentiation in hippocampal slices from adult and young rats. Toxicol. Lett. 165, 167-173, Krueger, K., Repges, H., Hippler, J., Hartmann, L.M., Hirner, A.V., Straub, H., Binding, N., Mu{beta}hoff, U., 2007. Effects of dimethylarsinic and dimethylarsinous acid on evoked synaptic potentials in hippocampal slices of young and adult rats. Toxicol. Appl. Pharmacol. 225, 40-46). The present experiments investigate, whether the important arsenic metabolites monomethylarsonic acid (MMA{sup V}) and monomethylarsonous acid (MMA{sup III}) also influence the synaptic functions of the hippocampus. In hippocampal slices of young (14-21 days-old) and adult (2-4 months-old) rats, evoked synaptic field potentials from the Schaffer collateral-CA1 synapse were measured under control conditions and during and after 30 and 60 min of application of the arsenic compounds. MMA{sup V} had no effect on the synapse functions neither in slices of adult nor in those from young rats. However, MMA{sup III} strongly influenced the synaptic transmission: it totally depressed the amplitudes of fEPSPs at concentrations of 50 {mu}mol/l (adult rats) and 25 {mu}mol/l (young rats) and LTP amplitudes at concentrations of 25 {mu}mol/l (adult rats) and 10 {mu}mol/l (young rats), respectively. In contrast, application of 1 {mu}mol/l MMA{sup III} led to an enhancement of the LTP amplitude in young rats, which is interpretable by an enhancing effect on NMDA receptors and a lack of the blocking effect on AMPA receptors at

  8. Simulation and experimental study of DC electric field distribution characteristics of rat hippocampal slices in vitro

    NASA Astrophysics Data System (ADS)

    Zheng, Yu; Dong, Lei; Gao, Yang; Qiu, Qian; Li, Ze-yan; Zhao, Zhe; Chen, Rui-juan; Wang, Hui-quan

    2016-06-01

    Direct current (DC) electric field is a noninvasive neuromodulation tool that can inhibit or facilitate excitability of neurons. Despite its efficacy, the dielectric constant of artificial cerebrospinal fluid and the position and direction of brain slices and other factors can affect the field intensity and distribution acting on the surface of rat hippocampus slices, thus causing errors. In this study, we describe a new analytical method optimized for DC electric fields acting on brain slices, and the design of an external DC electric field stimulator to allow scientific evaluation of brain slices. We investigated parameters regarding the uniformity of electric field distribution and identified the maximal parameters using the finite element method. Then, we selected and simplified slice images using magnetic resonance imaging data and calculated the electric field intensity of the original and simplified models. The electric field simulator induced action potential and excitatory postsynaptic current with intensities of 1, 5, and 10 V/m. This study describes the development of a new electric field stimulator and successfully demonstrates its practicability for scientific evaluation of tissue slices.

  9. Evidence for a Specific Integrative Mechanism for Episodic Memory Mediated by AMPA/kainate Receptors in a Circuit Involving Medial Prefrontal Cortex and Hippocampal CA3 Region.

    PubMed

    de Souza Silva, Maria A; Huston, Joseph P; Wang, An-Li; Petri, David; Chao, Owen Yuan-Hsin

    2016-07-01

    We asked whether episodic-like memory requires neural mechanisms independent of those that mediate its component memories for "what," "when," and "where," and if neuronal connectivity between the medial prefrontal cortex (mPFC) and the hippocampus (HPC) CA3 subregion is essential for episodic-like memory. Unilateral lesion of the mPFC was combined with unilateral lesion of the CA3 in the ipsi- or contralateral hemispheres in rats. Episodic-like memory was tested using a task, which assesses the integration of memories for "what, where, and when" concomitantly. Tests for novel object recognition (what), object place (where), and temporal order memory (when) were also applied. Bilateral disconnection of the mPFC-CA3 circuit by N-methyl-d-aspartate (NMDA) lesions disrupted episodic-like memory, but left the component memories for object, place, and temporal order, per se, intact. Furthermore, unilateral NMDA lesion of the CA3 plus injection of (6-cyano-7-nitroquinoxaline-2,3-dione) (CNQX) (AMPA/kainate receptor antagonist), but not AP-5 (NMDA receptor antagonist), into the contralateral mPFC also disrupted episodic-like memory, indicating the mPFC AMPA/kainate receptors as critical for this circuit. These results argue for a selective neural system that specifically subserves episodic memory, as it is not critically involved in the control of its component memories for object, place, and time. PMID:26048953

  10. Properties of Taurine Release in Glucose-Free Media in Hippocampal Slices from Developing and Adult Mice

    PubMed Central

    Oja, Simo S.; Saransaari, Pirjo

    2015-01-01

    The release of preloaded [3H]taurine from hippocampal slices from developing 7-day-old and young adult 3-month-old mice was studied in a superfusion system in the absence of glucose. These hypoglycemic conditions enhanced the release at both ages, the effect being markedly greater in developing mice. A depolarizing K+ concentration accentuated the release, which indicates that it was partially mediated by exocytosis. The anion channel blockers were inhibitory, witnessing the contribution of ion channels. NO-generating agents fomented the release as a sign of the participation of excitatory amino acid receptors. The other second messenger systems were apparently less efficient. The much greater taurine release could be a reason for the well-known greater tolerance of developing nervous tissue to lack of glucose. PMID:26347028

  11. Dopamine Modulates Spike Timing-Dependent Plasticity and Action Potential Properties in CA1 Pyramidal Neurons of Acute Rat Hippocampal Slices

    PubMed Central

    Edelmann, Elke; Lessmann, Volkmar

    2011-01-01

    Spike timing-dependent plasticity (STDP) is a cellular model of Hebbian synaptic plasticity which is believed to underlie memory formation. In an attempt to establish a STDP paradigm in CA1 of acute hippocampal slices from juvenile rats (P15–20), we found that changes in excitability resulting from different slice preparation protocols correlate with the success of STDP induction. Slice preparation with sucrose containing ACSF prolonged rise time, reduced frequency adaptation, and decreased latency of action potentials in CA1 pyramidal neurons compared to preparation in conventional ASCF, while other basal electrophysiological parameters remained unaffected. Whereas we observed prominent timing-dependent long-term potentiation (t-LTP) to 171 ± 10% of controls in conventional ACSF, STDP was absent in sucrose prepared slices. This sucrose-induced STDP deficit could not be rescued by stronger STDP paradigms, applying either more pre- and/or postsynaptic stimuli, or by a higher stimulation frequency. Importantly, slice preparation with sucrose containing ACSF did not eliminate theta-burst stimulation induced LTP in CA1 in field potential recordings in our rat hippocampal slices. Application of dopamine (for 10–20 min) to sucrose prepared slices completely rescued t-LTP and recovered action potential properties back to levels observed in ACSF prepared slices. Conversely, acute inhibition of D1 receptor signaling impaired t-LTP in ACSF prepared slices. No similar restoring effect for STDP as seen with dopamine was observed in response to the β-adrenergic agonist isoproterenol. ELISA measurements demonstrated a significant reduction of endogenous dopamine levels (to 61.9 ± 6.9% of ACSF values) in sucrose prepared slices. These results suggest that dopamine signaling is involved in regulating the efficiency to elicit STDP in CA1 pyramidal neurons. PMID:22065958

  12. NAAG reduces NMDA receptor current in CA1 hippocampal pyramidal neurons of acute slices and dissociated neurons.

    PubMed

    Bergeron, Richard; Coyle, Joseph T; Tsai, Guochan; Greene, Robert W

    2005-01-01

    N-acetylaspartylglutamate (NAAG) is an abundant neuropeptide in the nervous system, yet its functions are not well understood. Pyramidal neurons of the CA1 sector of acutely prepared hippocampal slices were recorded using the whole-cell patch-clamp technique. At low concentrations (20 microM), NAAG reduced isolated N-methyl-D-aspartate receptor (NMDAR)-mediated synaptic currents or NMDA-induced currents. The NAAG-induced change in the NMDA concentration/response curve suggested that the antagonism was not competitive. However, the NAAG-induced change in the concentration/response curve for the NMDAR co-agonist, glycine, indicated that glycine can overcome the NAAG antagonism. The antagonism of the NMDAR induced by NAAG was still observed in the presence of LY-341495, a potent and selective mGluR3 antagonist. Moreover, in dissociated pyramidal neurons of the CA1 region, NAAG also reduced the NMDA current and this effect was reversed by glycine. These results suggest that NAAG reduces the NMDA currents in hippocampal CA1 pyramidal neurons. PMID:15354184

  13. Excitatory and inhibitory synaptic transmission is differentially influenced by two ortho-substituted polychlorinated biphenyls in the hippocampal slice preparation

    SciTech Connect

    Kim, Kyung Ho; Inan, Salim Yalcin; Berman, Robert F.; Pessah, Isaac N.

    2009-06-01

    Exposure to polychlorinated biphenyls impairs cognition and behavior in children. Two environmental PCBs 2,2',3,3',4,4',5-heptachlorobiphenyl (PCB170) and 2,2',3,5',6-pentachlorobiphenyl (PCB95) were examined in vitro for influences on synaptic transmission in rat hippocampal slices. Field excitatory postsynaptic potentials (fEPSPs) were recorded in the CA1 region using a multi-electrode array. Perfusion with PCB170 (10 nM) had no effect on fEPSP slope relative to baseline period, whereas (100 nM) initially enhanced then depressed fEPSP slope. Perfusion of PCB95 (10 or 100 nM) persistently enhanced fEPSP slope > 200%, an effect that could be inhibited by dantrolene, a drug that attenuates ryanodine receptor signaling. Perfusion with picrotoxin (PTX) to block GABA neurotransmission resulted in a modest increase in fEPSP slope, whereas PTX + PCB170 (1-100 nM) persistently enhanced fEPSP slope in a dose dependent manner. fEPSP slope reached > 250% of baseline period in the presence of PTX + 100 nM PCB170, conditions that evoked marked epileptiform after-potential discharges. PCB95 and PCB170 were found to differentially influence the Ca{sup 2+}-dependence of [{sup 3}H]ryanodine-binding to hippocampal ryanodine receptors. Non-coplanar PCB congeners can differentially alter neurotransmission in a manner suggesting they can elicit imbalances between inhibitory and excitatory circuits within the hippocampus. Differential sensitization of ryanodine receptors by Ca{sup 2+} appears to mediate, at least in part, hippocampal excitotoxicity by non-coplanar PCBs.

  14. HIF-1α-mediated upregulation of SERCA2b: The endogenous mechanism for alleviating the ischemia-induced intracellular Ca(2+) store dysfunction in CA1 and CA3 hippocampal neurons.

    PubMed

    Kopach, Olga; Maistrenko, Anastasiia; Lushnikova, Iryna; Belan, Pavel; Skibo, Galina; Voitenko, Nana

    2016-05-01

    Pyramidal neurons of the hippocampus possess differential susceptibility to the ischemia-induced damage with the highest vulnerability of CA1 and the lower sensitivity of CA3 neurons. This damage is triggered by Ca(2+)-dependent excitotoxicity and can result in a delayed cell death that might be potentially suspended through activation of endogenous neuroprotection with the hypoxia-inducible transcription factors (HIF). However, the molecular mechanisms of this neuroprotection remain poorly understood. Here we show that prolonged (30min) oxygen and glucose deprivation (OGD) in situ impairs intracellular Ca(2+) regulation in CA1 rather than in CA3 neurons with the differently altered expression of genes coding Ca(2+)-ATPases: the mRNA level of plasmalemmal Ca(2+)-ATPases (PMCA1 and PMCA2 subtypes) was downregulated in CA1 neurons, whereas the mRNA level of the endoplasmic reticulum Ca(2+)-ATPases (SERCA2b subtype) was increased in CA3 neurons at 4h of re-oxygenation after prolonged OGD. These demonstrate distinct susceptibility of CA1 and CA3 neurons to the ischemic impairments in intracellular Ca(2+) regulation and Ca(2+)-ATPase expression. Stabilization of HIF-1α by inhibiting HIF-1α hydroxylation prevented the ischemic decrease in both PMCA1 and PMCA2 mRNAs in CA1 neurons, upregulated the SERCA2b mRNA level and eliminated the OGD-induced Ca(2+) store dysfunction in these neurons. Cumulatively, these findings reveal the previously unknown HIF-1α-driven upregulation of Ca(2+)-ATPases as a mechanism opposing the ischemic impairments in intracellular Ca(2+) regulation in hippocampal neurons. The ability of HIF-1α to modulate expression of genes coding Ca(2+)-ATPases suggests SERCA2b as a novel target for HIF-1 and may provide potential implications for HIF-1α-stabilizing strategy in activating endogenous neuroprotection. PMID:26969192

  15. Effects of dimethylarsinic and dimethylarsinous acid on evoked synaptic potentials in hippocampal slices of young and adult rats

    SciTech Connect

    Krueger, Katharina Repges, Hendrik; Hippler, Joerg; Hartmann, Louise M.; Hirner, Alfred V.; Straub, Heidrun; Binding, Norbert; Musshoff, Ulrich

    2007-11-15

    In this study, the effects of pentavalent dimethylarsinic acid ((CH{sub 3}){sub 2}AsO(OH); DMA{sup V}) and trivalent dimethylarsinous acid ((CH{sub 3}){sub 2}As(OH); DMA{sup III}) on synaptic transmission generated by the excitatory Schaffer collateral-CA1 synapse were tested in hippocampal slices of young (14-21 day-old) and adult (2-4 month-old) rats. Both compounds were applied in concentrations of 1 to 100 {mu}mol/l. DMA{sup V} had no effect on the amplitudes of evoked fEPSPs or the induction of LTP recorded from the CA1 dendritic region either in adult or in young rats. However, application of DMA{sup III} significantly reduced the amplitudes of evoked fEPSPs in a concentration-dependent manner with a total depression following application of 100 {mu}mol/l DMA{sup III} in adult and 10 {mu}mol/l DMA{sup III} in young rats. Moreover, DMA{sup III} significantly affected the LTP-induction. Application of 10 {mu}mol/l DMA{sup III} resulted in a complete failure of the postsynaptic potentiation of the fEPSP amplitudes in slices taken both from adult and young rats. The depressant effect was not reversible after a 30-min washout of the DMA{sup III}. In slices of young rats, the depressant effects of DMA{sup III} were more pronounced than in those taken from adult ones. Compared to the (absent) effect of DMA{sup V} on synaptic transmission, the trivalent compound possesses a considerably higher neurotoxic potential.

  16. Isolation of CA1 nuclear enriched fractions from hippocampal slices to study activity-dependent nuclear import of synapto-nuclear messenger proteins.

    PubMed

    Yuanxiang, Pingan; Bera, Sujoy; Karpova, Anna; Kreutz, Michael R; Mikhaylova, Marina

    2014-01-01

    Studying activity dependent protein expression, subcellular translocation, or phosphorylation is essential to understand the underlying cellular mechanisms of synaptic plasticity. Long-term potentiation (LTP) and long-term depression (LTD) induced in acute hippocampal slices are widely accepted as cellular models of learning and memory. There are numerous studies that use live cell imaging or immunohistochemistry approaches to visualize activity dependent protein dynamics. However these methods rely on the suitability of antibodies for immunocytochemistry or overexpression of fluorescence-tagged proteins in single neurons. Immunoblotting of proteins is an alternative method providing independent confirmation of the findings. The first limiting factor in preparation of subcellular fractions from individual tetanized hippocampal slices is the low amount of material. Second, the handling procedure is crucial because even very short and minor manipulations of living slices might induce activation of certain signaling cascades. Here we describe an optimized workflow in order to obtain sufficient quantity of nuclear enriched fraction of sufficient purity from the CA1 region of acute hippocampal slices from rat brain. As a representative example we show that the ERK1/2 phosphorylated form of the synapto-nuclear protein messenger Jacob actively translocates to the nucleus upon induction of LTP and can be detected in a nuclear enriched fraction from CA1 neurons. PMID:25145907

  17. Estradiol and the Relationship between Dendritic Spines, NR2B Containing NMDA Receptors, and the Magnitude of Long-Term Potentiation at Hippocampal CA3-CA1 Synapses

    PubMed Central

    Smith, Caroline C.; Vedder, Lindsey C.; McMahon, Lori L.

    2009-01-01

    Summary When circulating estrogen levels decline as a natural consequence of menopause and aging in women, there is an increased incidence of deficits in working memory. In many cases, these deficits are rescued by estrogen replacement therapy. These clinical data therefore highlight the importance of defining the biological pathways linking estrogen to the cellular substrates of learning and memory. It has been known for nearly two decades that estrogen enhances dendritic spine density on apical dendrites of CA1 pyramidal cells in hippocampus, a brain region required for learning. Interestingly, at synapses between CA3-CA1 pyramidal cells, estrogen has also been shown to enhance synaptic NMDA receptor current and the magnitude of long term potentiation, a cellular correlate of learning and memory. Given that synapse density, NMDAR function, and long term potentiation at CA3-CA1 synapses in hippocampus are associated with normal learning, it is likely that modulation of these parameters by estrogen facilitates the improvement in learning observed in rats, primates and humans following estrogen replacement. To facilitate the design of clinical strategies to potentially prevent or reverse the age-related decline in learning and memory during menopause, the relationship between the estrogen-induced morphological and functional changes in hippocampus must be defined and the role these changes play in facilitating learning must be elucidated. The aim of this report is to provide a summary of the proposed mechanisms by which this hormone increases synaptic function and in doing so, it briefly addresses potential mechanisms contributing to the estrogen-induced increase in synaptic morphology and plasticity, as well as important future directions. PMID:19596521

  18. Long-Term Potentiation at CA3–CA1 Hippocampal Synapses with Special Emphasis on Aging, Disease, and Stress

    PubMed Central

    Kumar, Ashok

    2011-01-01

    Synaptic plasticity in the mammalian central nervous system has been the subject of intense investigation for the past four decades. Long-term potentiation (LTP), a major reflection of synaptic plasticity, is an activity-driven long-lasting increase in the efficacy of excitatory synaptic transmission following the delivery of a brief, high-frequency train of electrical stimulation. LTP is regarded as a principal candidate for the cellular mechanisms involved in learning and offers an attractive hypothesis of how memories are constructed. There are a number of exceptional full-length reviews published on LTP; the current review intends to present an overview of the research findings regarding hippocampal LTP with special emphasis on aging, diseases, and psychological insults. PMID:21647396

  19. Fluoride Induces a Volume Reduction in CA1 Hippocampal Slices Via MAP Kinase Pathway Through Volume Regulated Anion Channels

    PubMed Central

    Lee, Jaekwang; Han, Young-Eun; Favorov, Oleg; Tommerdahl, Mark; Whitsel, Barry

    2016-01-01

    Regulation of cell volume is an important aspect of cellular homeostasis during neural activity. This volume regulation is thought to be mediated by activation of specific transporters, aquaporin, and volume regulated anion channels (VRAC). In cultured astrocytes, it was reported that swelling-induced mitogen-activated protein (MAP) kinase activation is required to open VRAC, which are thought to be important in regulatory volume decrease and in the response of CNS to trauma and excitotoxicity. It has been also described that sodium fluoride (NaF), a recognized G-protein activator and protein phosphatase inhibitor, leads to a significant MAP kinase activation in endothelial cells. However, NaF's effect in volume regulation in the brain is not known yet. Here, we investigated the mechanism of NaF-induced volume change in rat and mouse hippocampal slices using intrinsic optical signal (IOS) recording, in which we measured relative changes in intracellular and extracellular volume as changes in light transmittance through brain slices. We found that NaF (1~5 mM) application induced a reduction in light transmittance (decreased volume) in CA1 hippocampus, which was completely reversed by MAP kinase inhibitor U0126 (10 µM). We also observed that NaF-induced volume reduction was blocked by anion channel blockers, suggesting that NaF-induced volume reduction could be mediated by VRAC. Overall, our results propose a novel molecular mechanism of NaF-induced volume reduction via MAP kinase signaling pathway by activation of VRAC. PMID:27122993

  20. Fluoride Induces a Volume Reduction in CA1 Hippocampal Slices Via MAP Kinase Pathway Through Volume Regulated Anion Channels.

    PubMed

    Lee, Jaekwang; Han, Young-Eun; Favorov, Oleg; Tommerdahl, Mark; Whitsel, Barry; Lee, C Justin

    2016-04-01

    Regulation of cell volume is an important aspect of cellular homeostasis during neural activity. This volume regulation is thought to be mediated by activation of specific transporters, aquaporin, and volume regulated anion channels (VRAC). In cultured astrocytes, it was reported that swelling-induced mitogen-activated protein (MAP) kinase activation is required to open VRAC, which are thought to be important in regulatory volume decrease and in the response of CNS to trauma and excitotoxicity. It has been also described that sodium fluoride (NaF), a recognized G-protein activator and protein phosphatase inhibitor, leads to a significant MAP kinase activation in endothelial cells. However, NaF's effect in volume regulation in the brain is not known yet. Here, we investigated the mechanism of NaF-induced volume change in rat and mouse hippocampal slices using intrinsic optical signal (IOS) recording, in which we measured relative changes in intracellular and extracellular volume as changes in light transmittance through brain slices. We found that NaF (1~5 mM) application induced a reduction in light transmittance (decreased volume) in CA1 hippocampus, which was completely reversed by MAP kinase inhibitor U0126 (10 µM). We also observed that NaF-induced volume reduction was blocked by anion channel blockers, suggesting that NaF-induced volume reduction could be mediated by VRAC. Overall, our results propose a novel molecular mechanism of NaF-induced volume reduction via MAP kinase signaling pathway by activation of VRAC. PMID:27122993

  1. Neuroprotection Promoted by Guanosine Depends on Glutamine Synthetase and Glutamate Transporters Activity in Hippocampal Slices Subjected to Oxygen/Glucose Deprivation.

    PubMed

    Dal-Cim, Tharine; Martins, Wagner C; Thomaz, Daniel T; Coelho, Victor; Poluceno, Gabriela Godoy; Lanznaster, Débora; Vandresen-Filho, Samuel; Tasca, Carla I

    2016-05-01

    Guanosine (GUO) has been shown to act as a neuroprotective agent against glutamatergic excitotoxicity by increasing glutamate uptake and decreasing its release. In this study, a putative effect of GUO action on glutamate transporters activity modulation was assessed in hippocampal slices subjected to oxygen and glucose deprivation (OGD), an in vitro model of brain ischemia. Slices subjected to OGD showed increased excitatory amino acids release (measured by D-[(3)H]aspartate release) that was prevented in the presence of GUO (100 µM). The glutamate transporter blockers, DL-TBOA (10 µM), DHK (100 µM, selective inhibitor of GLT-1), and sulfasalazine (SAS, 250 µM, Xc(-) system inhibitor) decreased OGD-induced D-aspartate release. Interestingly, DHK or DL-TBOA blocked the decrease in glutamate release induced by GUO, whereas SAS did not modify the GUO effect. GUO protected hippocampal slices from cellular damage by modulation of glutamate transporters, however selective blockade of GLT-1 or Xc- system only did not affect this protective action of GUO. OGD decreased hippocampal glutamine synthetase (GS) activity and GUO recovered GS activity to control levels without altering the kinetic parameters of GS activity, thus suggesting GUO does not directly interact with GS. Additionally, the pharmacological inhibition of GS activity with methionine sulfoximine abolished the effect of GUO in reducing D-aspartate release and cellular damage evoked by OGD. Altogether, results in hippocampal slices subjected to OGD show that GUO counteracts the release of excitatory amino acids, stimulates the activity of GS, and decreases the cellular damage by modulation of glutamate transporters activity. PMID:26858177

  2. Assessment of Tissue Viability Following Electroosmotic Push–Pull Perfusion from Organotypic Hippocampal Slice Cultures

    PubMed Central

    2013-01-01

    We have developed a novel sampling technique that allows both introduction and removal of fluid from the extracellular space of living tissue. This method is based on the fluidics of push–pull perfusion but flow is driven by electroosmosis. We have applied this method to organotypic hippocampal cultures. A source capillary is inserted into the tissue and a collection capillary is in contact with the tissue surface through a thin layer of fluid. A voltage is applied across the proximal ends of source and collection capillary. In the applied field, fluid will move from source, into the tissue, and then be collected. In this process, damage to cells may occur. To understand better what sampling conditions influence damage most, we tested various sampling geometries and applied voltages, quantifying damage 16–24 h later using propidium iodide as a cell death marker. We found that damage correlates with both voltage drop and power dissipated in the tissue, but that voltage drop is a better indicator of damage when comparing models in which capillary arrangement and length are different. PMID:23639590

  3. How To Record a Million Synaptic Weights in a Hippocampal Slice

    PubMed Central

    Bhalla, Upinder S.

    2008-01-01

    A key step toward understanding the function of a brain circuit is to find its wiring diagram. New methods for optical stimulation and optical recording of neurons make it possible to map circuit connectivity on a very large scale. However, single synapses produce small responses that are difficult to measure on a large scale. Here I analyze how single synaptic responses may be detectable using relatively coarse readouts such as optical recording of somatic calcium. I model a network consisting of 10,000 input axons and 100 CA1 pyramidal neurons, each represented using 19 compartments with voltage-gated channels and calcium dynamics. As single synaptic inputs cannot produce a measurable somatic calcium response, I stimulate many inputs as a baseline to elicit somatic action potentials leading to a strong calcium signal. I compare statistics of responses with or without a single axonal input riding on this baseline. Through simulations I show that a single additional input shifts the distribution of the number of output action potentials. Stochastic resonance due to probabilistic synaptic release makes this shift easier to detect. With ∼80 stimulus repetitions this approach can resolve up to 35% of individual activated synapses even in the presence of 20% recording noise. While the technique is applicable using conventional electrical stimulation and extracellular recording, optical methods promise much greater scaling, since the number of synapses scales as the product of the number of inputs and outputs. I extrapolate from current high-speed optical stimulation and recording methods, and show that this approach may scale up to the order of a million synapses in a single two-hour slice-recording experiment. PMID:18566658

  4. Regulating hippocampal hyperexcitability through GABAB Receptors

    PubMed Central

    Lang, Min; Moradi‐Chameh, Homeira; Zahid, Tariq; Gane, Jonathan; Wu, Chiping; Valiante, Taufik; Zhang, Liang

    2014-01-01

    Abstract Disturbances of GABAergic inhibition are a major cause of epileptic seizures. GABA exerts its actions via ionotropic GABAA receptors and metabotropic G protein‐coupled GABAB receptors. Malfunction of GABAA inhibition has long been recognized in seizure genesis but the role of GABAB receptors in controlling seizure activity is still not well understood. Here, we examined the anticonvulsive, or inhibitory effects, of GABAB receptors in a mouse model of hippocampal kindling as well as mouse hippocampal slices through the use of GS 39783, a positive allosteric GABAB receptor modulator, and CGP 55845, a selective GABAB receptor antagonist. When administered via intraperitoneal injections in kindled mice, GS 39783 (5 mg/kg) did not attenuate hippocampal EEG discharges, but did reduce aberrant hippocampal spikes, whereas CGP 55845 (10 mg/kg) prolonged hippocampal discharges and increased spike incidences. When examined in hippocampal slices, neither GS 39783 at 5 μmol/L nor the GABAB receptor agonist baclofen at 0.1 μmol/L alone significantly altered repetitive excitatory field potentials, but GS 39783 and baclofen together reversibly abolished these field potentials. In contrast, CGP 55845 at 1 μmol/L facilitated induction and incidence of these field potentials. In addition, CGP 55845 attenuated the paired pulse depression of CA3 population spikes and increased the frequency of EPSCs in individual CA3 pyramidal neurons. Collectively, these data suggest that GABABB receptors regulate hippocampal hyperexcitability by inhibiting CA3 glutamatergic synapses. We postulate that positive allosteric modulation of GABAB receptors may be effective in reducing seizure‐related hyperexcitability. PMID:24771688

  5. Ontogeny of kainate-induced gamma oscillations in the rat CA3 hippocampus in vitro

    PubMed Central

    Tsintsadze, Vera; Minlebaev, Marat; Suchkov, Dimitry; Cunningham, Mark O.; Khazipov, Roustem

    2015-01-01

    GABAergic inhibition, which is instrumental in the generation of hippocampal gamma oscillations, undergoes significant changes during development. However, the development of hippocampal gamma oscillations remains largely unknown. Here, we explored the developmental features of kainate-induced oscillations (KA-Os) in CA3 region of rat hippocampal slices. Up to postnatal day P5, the bath application of kainate failed to evoke any detectable oscillations. KA-Os emerged by the end of the first postnatal week; these were initially weak, slow (20–25 Hz, beta range) and were poorly synchronized with CA3 units and synaptic currents. Local field potential (LFP) power, synchronization of units and frequency of KA-Os increased during the second postnatal week to attain gamma (30–40 Hz) frequency by P15–21. Both beta and gamma KA-Os are characterized by alternating sinks and sources in the pyramidal cell layer, likely generated by summation of the action potential—associated currents and GABAergic synaptic currents, respectively. Blockade of GABA(A) receptors with gabazine completely suppressed KA-Os at all ages indicating that GABAergic mechanisms are instrumental in their generation. Bumetanide, a NKCC1 chloride co-transporter antagonist which renders GABAergic responses inhibitory in the immature hippocampal neurons, failed to induce KA-Os at P2–4 indicating that the absence of KA-Os in neonates is not due to depolarizing actions of GABA. The linear developmental profile, electrographic features and pharmacological properties indicate that CA3 hippocampal beta and gamma KA-Os are fundamentally similar in their generative mechanisms and their delayed onset and developmental changes likely reflect the development of perisomatic GABAergic inhibition. PMID:26041996

  6. No evidence for role of extracellular choline-acetyltransferase in generation of gamma oscillations in rat hippocampal slices in vitro.

    PubMed

    Hollnagel, J O; ul Haq, R; Behrens, C J; Maslarova, A; Mody, I; Heinemann, U

    2015-01-22

    Acetylcholine (ACh) is well known to induce persistent γ-oscillations in the hippocampus when applied together with physostigmine, an inhibitor of the ACh degrading enzyme acetylcholinesterase (AChE). Here we report that physostigmine alone can also dose-dependently induce γ-oscillations in rat hippocampal slices. We hypothesized that this effect was due to the presence of choline in the extracellular space and that this choline is taken up into cholinergic fibers where it is converted to ACh by the enzyme choline-acetyltransferase (ChAT). Release of ACh from cholinergic fibers in turn may then induce γ-oscillations. We therefore tested the effects of the choline uptake inhibitor hemicholinium-3 (HC-3) on persistent γ-oscillations either induced by physostigmine alone or by co-application of ACh and physostigmine. We found that HC-3 itself did not induce γ-oscillations and also did not prevent physostigmine-induced γ-oscillation while washout of physostigmine and ACh-induced γ-oscillations was accelerated. It was recently reported that ChAT might also be present in the extracellular space (Vijayaraghavan et al., 2013). Here we show that the effect of physostigmine was prevented by the ChAT inhibitor (2-benzoylethyl)-trimethylammonium iodide (BETA) which could indicate extracellular synthesis of ACh. However, when we tested for effects of extracellularly applied acetyl-CoA, a substrate of ChAT for synthesis of ACh, physostigmine-induced γ-oscillations were attenuated. Together, these findings do not support the idea that ACh can be synthesized by an extracellularly located ChAT. PMID:25453770

  7. Resveratrol protects against oxidative injury induced by H2O2 in acute hippocampal slice preparations from Wistar rats.

    PubMed

    de Almeida, Lúcia Maria Vieira; Leite, Marina Concli; Thomazi, Ana Paula; Battu, Cíntia; Nardin, Patrícia; Tortorelli, Lucas Silva; Zanotto, Caroline; Posser, Thaís; Wofchuk, Susana Tchernin; Leal, Rodrigo Bainy; Gonçalves, Carlos-Alberto; Gottfried, Carmem

    2008-12-01

    There is a current interest in dietary compounds (such as trans-resveratrol) that can inhibit or reverse oxidative stress, the common pathway for a variety of brain disorders, including Alzheimer's disease and stroke. The objective of the present study was to investigate the effects of resveratrol, under conditions of oxidative stress induced by H(2)O(2), on acute hippocampal slices from Wistar rats. Here, we evaluated cell viability, extracellular lactate, glutathione content, ERK(MAPK) activity, glutamate uptake and S100B secretion. Resveratrol did not change the decrease in lactate levels and in cell viability (by MTT assay) induced by 1mM H(2)O(2), but prevented the increase in cell permeability to Trypan blue induced by H(2)O(2). Moreover, resveratrol per se increased total glutathione levels and prevented the decrease in glutathione induced by 1mM H(2)O(2). The reduction of S100B secretion induced by H(2)O(2) was not changed by resveratrol. Glutamate uptake was decreased in the presence of 1mM H(2)O(2) and this effect was not prevented by resveratrol. There was also a significant activation of ERK1/2 by 1mM H(2)O(2) and resveratrol was able to completely prevent this activation, leading to activity values lower than control levels. The impairments in astrocyte activities, induced by H(2)O(2), confirmed the importance of these cells as targets for therapeutic strategy in brain disorders involving oxidative stress. This study reinforces the protective role of resveratrol and indicates some possible molecular sites of activity of this compound on glial cells, in the acute damage of brain tissue during oxidative stress. PMID:18835240

  8. Non-specific inhibitors of aquaporin-4 stimulate S100B secretion in acute hippocampal slices of rats.

    PubMed

    Zanotto, Caroline; Abib, Renata Torres; Batassini, Cristiane; Tortorelli, Lucas Silva; Biasibetti, Regina; Rodrigues, Letícia; Nardin, Patrícia; Hansen, Fernanda; Gottfried, Carmem; Leite, Marina Concli; Gonçalves, Carlos-Alberto

    2013-01-23

    Aquaporin-4 (AQP-4) is the principal brain water channel and is predominantly expressed in astrocytes suggesting its dynamic involvement in water homeostasis in brain tissue. Due to the co-localization of AQP-4 and inward rectifier K(+) channels Kir 4.1, a functional coupling between these proteins has been proposed. AQP-4 has a putative role in the physiopathology of brain disorders including epilepsy and trauma. S100B is a calcium-binding protein expressed and secreted by astrocytes, and commonly used as a parameter of astroglial activation. Here, we investigate a possible link between AQP-4 activity (and Kir 4.1) and S100B secretion in hippocampal slices of rats of different ages using non-specific inhibitors of AQP-4 (AZA, acetazolamide and TEA, tetraethylammonium) and Kir 4.1 (barium chloride). We found that blockade of AQP-4 with TEA and AZA produced an increase in S100B secretion in young rats, compatible with an astroglial activation observed in many conditions of brain injury. On the other hand, BaCl(2) induced Kir 4.1 inhibition caused a decrease in S100B secretion. Both channels, AQP-4 and Kir 4.1, exhibited a similar ontogenetic profile, in spite of the functional uncoupling, in relation to S100B secretion. Moreover, we found a significant increase in the S100B secretion basal levels with the increasing of animal age and the incubation with high levels of potassium resulted in a decrease of S100B secretion in 30 and 90-day old rats. These data, together with previous observations from gap junctions and glutamate transport of astrocytes, contribute to characterize the operational system involving astroglial activation, particularly on S100B secretion, in brain disorders. PMID:23142267

  9. Time-dependent reversal of long-term potentiation by brief cooling shocks in rat hippocampal slices.

    PubMed

    Bittar, P; Muller, D

    1993-08-27

    Using a recording chamber built with peltier elements, we studied the effects of fast and brief reductions in temperature on synaptic transmission and plasticity in area CA1 of rat hippocampal slices. Cooling shocks consisted of a drop in temperature from 33 degrees C to 30 degrees C, 27 degrees C or 24 degrees C for 2-5 min. Equilibrium to the new temperature was reached in about 30 s. During these cooling episodes, marked modifications of the size and time course of synaptic responses were observed. Changing the temperature for 4-5 min from 33 degrees C to 24 degrees C resulted in a 75% reduction in amplitude and 158% prolongation of the rise time of excitatory postsynaptic potentials (EPSPs). These changes were followed by a complete recovery of synaptic transmission. This recovery was very fast for the EPSP rise time (about 30 s), but much slower for the amplitude or initial slope (20-30 min). This slow recovery was correlated with changes in size of the presynaptic fiber volley, thereby indicating transient modifications of cell excitability. Application of cooling episodes of 4-5 min from 33 degrees C to 24 degrees C during the first 20 min that followed induction of long-term potentiation resulted in a complete reversal of synaptic potentiation. The LTP abolished by a cooling shock could be reinstated by re-applying high frequency trains. Several sequential induction/abolition effects could thus be obtained. In contrast, cooling episodes applied later than 25 min after LTP induction did not affect synaptic potentiation.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:8396492

  10. Drug Resistance in Cortical and Hippocampal Slices from Resected Tissue of Epilepsy Patients: No Significant Impact of P-Glycoprotein and Multidrug Resistance-Associated Proteins

    PubMed Central

    Sandow, Nora; Kim, Simon; Raue, Claudia; Päsler, Dennis; Klaft, Zin-Juan; Antonio, Leandro Leite; Hollnagel, Jan Oliver; Kovacs, Richard; Kann, Oliver; Horn, Peter; Vajkoczy, Peter; Holtkamp, Martin; Meencke, Heinz-Joachim; Cavalheiro, Esper A.; Pragst, Fritz; Gabriel, Siegrun; Lehmann, Thomas-Nicolas; Heinemann, Uwe

    2015-01-01

    Drug resistant patients undergoing epilepsy surgery have a good chance to become sensitive to anticonvulsant medication, suggesting that the resected brain tissue is responsible for drug resistance. Here, we address the question whether P-glycoprotein (Pgp) and multidrug resistance-associated proteins (MRPs) expressed in the resected tissue contribute to drug resistance in vitro. Effects of anti-epileptic drugs [carbamazepine (CBZ), sodium valproate, phenytoin] and two unspecific inhibitors of Pgp and MRPs [verapamil (VPM) and probenecid (PBN)] on seizure-like events (SLEs) induced in slices from 35 hippocampal and 35 temporal cortex specimens of altogether 51 patients (161 slices) were studied. Although in slice preparations the blood brain barrier is not functional, we found that SLEs predominantly persisted in the presence of anticonvulsant drugs (90%) and also in the presence of VPM and PBN (86%). Following subsequent co-administration of anti-epileptic drugs and drug transport inhibitors, SLEs continued in 63% of 143 slices. Drug sensitivity in slices was recognized either as transition to recurrent epileptiform transients (30%) or as suppression (7%), particularly by perfusion with CBZ in PBN containing solutions (43, 9%). Summarizing responses to co-administration from more than one slice per patient revealed that suppression of seizure-like activity in all slices was only observed in 7% of patients. Patients whose tissue was completely or partially sensitive (65%) presented with higher seizure frequencies than those with resistant tissue (35%). However, corresponding subgroups of patients do not differ with respect to expression rates of drug transporters. Our results imply that parenchymal MRPs and Pgp are not responsible for drug resistance in resected tissue. PMID:25741317

  11. Paired Burst Stimulation Causes GABAA Receptor-Dependent Spike Firing Facilitation in CA1 of Rat Hippocampal Slices

    PubMed Central

    Tominaga, Takashi; Tominaga, Yoko

    2016-01-01

    The theta oscillation (4–8 Hz) is a pivotal form of oscillatory activity in the hippocampus that is intermittently concurrent with gamma (25–100 Hz) burst events. In in vitro preparation, a stimulation protocol that mimics the theta oscillation, theta burst stimulation (TBS), is used to induce long-term potentiation. Thus, TBS is thought to have a distinct role in the neural network of the hippocampal slice preparation. However, the specific mechanisms that make TBS induce such neural circuit modifications are still unknown. Using electrophysiology and voltage-sensitive dye imaging (VSDI), we have found that TBS induces augmentation of spike firing. The augmentation was apparent in the first couple of brief burst stimulation (100 Hz four pulses) on a TBS-train in a presence of NMDA receptor blocker (APV 50 μM). In this study, we focused on the characterizes of the NMDA independent augmentation caused by a pair of the brief burst stimulation (the first pair of the TBS; paired burst stimulation-PBS). We found that PBS enhanced membrane potential responses on VSDI signal and intracellular recordings while it was absent in the current recording under whole-cell clamp condition. The enhancement of the response accompanied the augmentation of excitatory postsynaptic potential (EPSP) to spike firing (E-S) coupling. The paired burst facilitation (PBF) reached a plateau when the number of the first burst stimulation (priming burst) exceeds three. The interval between the bursts of 150 ms resulted in the maximum PBF. Gabazine (a GABAA receptor antagonist) abolished PBF. The threshold for spike generation of the postsynaptic cells measured with a current injection to cells was not lowered by the priming burst of PBS. These results indicate that PBS activates the GABAergic system to cause short-term E-S augmentation without raising postsynaptic excitability. We propose that a GABAergic system of area CA1 of the hippocampus produce the short-term E-S plasticity that could

  12. The anticonvulsant actions of σ receptor ligands in the Mg2+-free model of epileptiform activity in rat hippocampal slices

    PubMed Central

    Thurgur, Claire; Church, John

    1998-01-01

    The anticonvulsant potency of a series of structurally-dissimilar compounds which possess nanomolar affinities for high-affinity σ binding sites was examined in the Mg2+-free model of epileptiform activity in rat hippocampal slices. Extracellular field potential recordings in the CA1 region were employed to examine the effects of test compounds on spontaneous epileptiform activity and multiple population spikes evoked by stimulation of the Schaffer collateral-commissural pathway.Applied at σ site-selective (i.e. nanomolar) concentrations, dextromethorphan, ditolylguanidine, caramiphen and opipramol failed to modify Mg2+-free epileptiform activity; neither pro- nor anticonvulsant effects were observed. However, applied at micromolar concentrations, these and additional test compounds reversibly inhibited orthodromically-evoked epileptiform field potentials with a rank order potency (IC50 values in μM): dextrorphan (1.5)>ifenprodil (6.3)>dextromethorphan (10)>ditolylguanidine (15)>loperamide (28)>carbetapentane (38)>caramiphen (46)>opipramol (52). Micromolar concentrations of the same compounds also inhibited spontaneous epileptiform bursts recorded during perfusion with Mg2+-free medium.Co-application of ropizine (10 μM), an allosteric modulator of dextromethorphan binding to high-affinity σ receptors, failed to endow dextromethorphan 10 nM with anticonvulsant properties and did not modify the anticonvulsant potency of 10 μM dextromethorphan.The effects of dextrorphan (10 μM), ifenprodil (20 μM), loperamide (50 μM) and caramiphen (100 μM) were examined in the presence of external Mg2+ on field potential input/output (I/O) relationships and paired-pulse facilitation (PPF) of field excitatory postsynaptic potentials. Only caramiphen elicited effects on these parameters, affecting synaptic transmission at the point of synaptic transfer and depressing PPF ratios to below baseline values. The effects of caramiphen on I/O relationships mimicked

  13. Neuroprotective effect of exercise in rat hippocampal slices submitted to in vitro ischemia is promoted by decrease of glutamate release and pro-apoptotic markers.

    PubMed

    Mourão, Flávio Afonso Gonçalves; Leite, Hércules Ribeiro; de Carvalho, Luciana Estefani Drumond; Ferreira E Vieira, Talita Hélen; Pinto, Mauro Cunha Xavier; de Castro Medeiros, Daniel; Andrade, Ian Lara Lamounier; Gonçalves, Daniela Fontes; Pereira, Grace Schenatto; Dutra Moraes, Márcio Flávio; Massensini, André Ricardo

    2014-10-01

    The role of physical exercise as a neuroprotective agent against ischemic injury has been extensively discussed. Nevertheless, the mechanisms underlying the effects of physical exercise on cerebral ischemia remain poorly understood. Here, we investigate the hypothesis that physical exercise increases ischemic tolerance by decreasing the induction of cellular apoptosis and glutamate release. Rats (n = 50) were submitted to a swimming exercise protocol for 8 weeks. Hippocampal slices were then submitted to oxygen and glucose deprivation. Cellular viability, pro-apoptotic markers (Caspase 8, Caspase 9, Caspase 3, and apoptosis-inducing factor), and glutamate release were analyzed. The percentage of cell death, the amount of glutamate release, and the expression of the apoptotic markers were all decreased in the exercise group when compared to the sedentary group after oxygen and glucose deprivation. Our results suggest that physical exercise protects hippocampal slices from the effects of oxygen and glucose deprivation, probably by a mechanism involving both the decrease of glutamatergic excitotoxicity and apoptosis induction. PMID:24903976

  14. Chemokine CCL2 enhances NMDA receptor-mediated excitatory postsynaptic current in rat hippocampal slices-a potential mechanism for HIV-1-associated neuropathy?

    PubMed

    Zhou, Yan; Tang, Hongmei; Xiong, Huangui

    2016-06-01

    Human immunodeficiency virus type 1 (HIV-1)-infected mononuclear phagocytes (brain macrophages and microglial cells) release proinflammatory cytokines and chemokines. Elevated levels of chemokine CC motif ligand 2 (CCL2, known previously as monocyte chemoattractant protein-1) have been detected in serum and cerebrospinal fluid (CSF) of HIV-1-infected individuals and the raised CCL2 in the CSF correlates with HIV-1-associated neurocognitive disorders. To understand how elevated CCL2 induces HIV-1-associated neuropathy, we studied effects of CCL2 on excitatory postsynaptic current (EPSCs) in the CA1 region of rat hippocampal brain slices using whole-cell patch recording techniques. The AMPA receptor (AMPAR)-mediated EPSC (EPSCAMPAR) and N-Methyl-D-aspartate (NMDA) receptor (NMDAR)-mediated EPSCs (EPSCNMDAR) were isolated pharmacologically. Bath application of CCL2 produced a significant enhancement of the amplitudes of EPSCs, EPSCAMPAR and EPSCNMDAR. Further studies revealed that CCL2 potentiated NMDAR subtype NR2A-mediated EPSC (EPSCNR2AR) and NR2B-mediated EPSC (EPSCNR2BR). To determine the site of action, we recorded spontaneous mini EPSCs (mEPSC) before and during bath application of CCL2. Our results showed that CCL2 decreased inter event interval (IEI) and increased the frequency of mEPSCs without change on the amplitude, suggesting a presynaptic site of CCL2 action. CCL2 was also found to injure primary rat hippocampal neuronal cultures and neuronal dendrites in the CA1 region of hippocampal slices. The CCL2-associated neuronal and dendritic injuries were blocked by a specific NMDAR antagonist or by a CCR2 receptor antagonist, indicating that CCL2-associated neural injury was mediated via NMDARs and/or CCR2 receptors. Taken together, these results suggest a potential role CCL2 may play in HIV-1-associated neuropathology. PMID:26968849

  15. Astrocyte origin of activity-dependent release of ATP and glutamate in hippocampal slices: real-time measurement utilizing microelectrode biosensors

    PubMed Central

    Sershen, Henry

    2012-01-01

    It is well known that astrocytic and neuronal transmitter release processes are important for signalling, and that activity-dependent release of adenosine nucleotides and transmitters occurs after stimulation. Neurons and astrocytes can account for the source of ATP efflux. In this issue of the BJP, Heinrich et al. characterized K+ depolarization-evoked release of ATP, adenosine and glutamate in hippocampal slices, utilizing microelectrode biosensors for simultaneous real-time recordings of multiple transmitter effluxes. They demonstrated efflux of ATP, adenosine and glutamate from hippocampus slices, in response to K+-depolarization, with distinct kinetics and mechanisms, suggesting a coordinated pattern of transmitter release. Surprisingly, it turned out that a considerable amount of the transmitter efflux measured under these conditions had a glial origin. For a long time, it was believed that the glial cell did not play a major role in neurotransmission, but the latter results somewhat change this view. The release of ATP and glutamate from glial cells under these conditions involved P2X7 receptors, and a source of adenosine accumulation independent of the metabolism of extracellular ATP was identified. This study also highlighted a novel use of multi-enzymatic microelectrode biosensors, which enabled a better characterization of transmitter release processes with higher temporal and spatial resolution than obtained previously. This technique was originally developed and used for the detection of purine release. In the present study, it was modified to identify the interplay between different transmitters, measured simultaneously in hippocampal slices. LINKED ARTICLE This article is a commentary on Heinrich et al., pp. 1003–1020 of this issue. To view this paper visit http://dx.doi.org/10.1111/j.1476-5381.2012.01932.x PMID:22703189

  16. Neuronal migration and its disorders affecting the CA3 region

    PubMed Central

    Belvindrah, Richard; Nosten-Bertrand, Marika; Francis, Fiona

    2014-01-01

    In this review, we focus on CA3 neuronal migration disorders in the rodent. We begin by introducing the main steps of hippocampal development, and we summarize characteristic hippocampal malformations in human. We then describe various mouse mutants showing structural hippocampal defects. Notably, genes identified in human cortical neuronal migration disorders consistently give rise to a CA3 phenotype when mutated in the mouse. We successively describe their molecular, physiological and behavioral phenotypes that together contribute to a better understanding of CA3-dependent functions. We finally discuss potential factors underlying the CA3 vulnerability revealed by these mouse mutants and that may also contribute to other human neurological and psychiatric disorders. PMID:24624057

  17. GABA release by hippocampal astrocytes

    PubMed Central

    Le Meur, Karim; Mendizabal-Zubiaga, Juan; Grandes, Pedro; Audinat, Etienne

    2012-01-01

    Astrocytes can directly influence neuronal activity through the release of various transmitters acting on membrane receptors expressed by neurons. However, in contrast to glutamate and ATP for instance, the release of GABA (γ-amino-butyric acid) by astrocytes is still poorly documented. Here, we used whole-cell recordings in rat acute brain slices and electron microscopy to test whether hippocampal astrocytes release the inhibitory transmitter GABA. We observed that slow transient inhibitory currents due to the activation of GABAA receptors occur spontaneously in principal neurons of the three main hippocampal fields (CA1, CA3, and dentate gyrus). These currents share characteristics with the slow NMDA receptor-mediated currents previously shown to result from astrocytic glutamate release: they occur in the absence of synaptic transmission and have variable kinetics and amplitudes as well as low frequencies. Osmotic pressure reduction, known to enhance transmitter release from astrocytes, similarly increased the frequency of non-synaptic GABA and glutamate currents. Simultaneous occurrence of slow inhibitory and excitatory currents was extremely rare. Yet, electron microscopy examination of immunostained hippocampal sections shows that about 80% of hippocampal astrocytes [positive for glial fibrillary acidic protein (GFAP)] were immunostained for GABA. Our results provide quantitative characteristics of the astrocyte-to-neuron GABAergic signaling. They also suggest that all principal neurons of the hippocampal network are under a dual, excitatory and inhibitory, influence of astrocytes. The relevance of the astrocytic release of GABA, and glutamate, on the physiopathology of the hippocampus remains to be established. PMID:22912614

  18. Nonlinear dynamical model based control of in vitro hippocampal output

    PubMed Central

    Hsiao, Min-Chi; Song, Dong; Berger, Theodore W.

    2012-01-01

    This paper describes a modeling-control paradigm to control the hippocampal output (CA1 response) for the development of hippocampal prostheses. In order to bypass a damaged hippocampal region (e.g., CA3), downstream hippocampal signal (e.g., CA1 responses) needs to be reinstated based on the upstream hippocampal signal (e.g., dentate gyrus responses) via appropriate stimulations to the downstream (CA1) region. In this approach, we optimize the stimulation signal to CA1 by using a predictive DG-CA1 nonlinear model (i.e., DG-CA1 trajectory model) and an inversion of the CA1 input–output model (i.e., inverse CA1 plant model). The desired CA1 responses are first predicted by the DG-CA1 trajectory model and then used to derive the optimal stimulation intensity through the inverse CA1 plant model. Laguerre-Volterra kernel models for random-interval, graded-input, contemporaneous-graded-output system are formulated and applied to build the DG-CA1 trajectory model and the CA1 plant model. The inverse CA1 plant model to transform desired output to input stimulation is derived from the CA1 plant model. We validate this paradigm with rat hippocampal slice preparations. Results show that the CA1 responses evoked by the optimal stimulations accurately replicate the CA1 responses recorded in the hippocampal slice with intact trisynaptic pathway. PMID:23429994

  19. S100B secretion is stimulated by IL-1beta in glial cultures and hippocampal slices of rats: Likely involvement of MAPK pathway.

    PubMed

    de Souza, Daniela F; Leite, Marina C; Quincozes-Santos, André; Nardin, Patrícia; Tortorelli, Lucas S; Rigo, Maurício M; Gottfried, Carmem; Leal, Rodrigo B; Gonçalves, Carlos-Alberto

    2009-01-01

    S100B is an astrocyte-derived cytokine implicated in the IL-1beta-triggered cytokine cycle in Alzheimer's disease. However, the secretion of S100B following stimulation by IL-1beta has not been directly demonstrated. We investigated S100B secretion in cortical primary astrocyte cultures, C6 glioma cells and acute hippocampal slices exposed to IL-1beta. S100B secretion was induced by IL-1beta in all preparations, involving MAPK pathway and, apparently, NF-small ka, CyrillicB signaling. Astrocytes and C6 cells exhibited different sensitivities to IL-1beta. These results suggest that IL-1beta-induced S100B secretion is a component of the neuroinflammatory response, which would support the involvement of S100B in the genesis of neurodegenerative diseases. PMID:19042033

  20. The tricyclic antidepressant desipramine inhibited the neurotoxic, kainate-induced [Ca(2+)]i increases in CA1 pyramidal cells in acute hippocampal slices.

    PubMed

    Koncz, István; Szász, Bernadett K; Szabó, Szilárd I; Kiss, János P; Mike, Arpád; Lendvai, Balázs; Sylvester Vizi, E; Zelles, Tibor

    2014-05-01

    Kainate (KA), used for modelling neurodegenerative diseases, evokes excitotoxicity. However, the precise mechanism of KA-evoked [Ca(2+)]i increase is unexplored, especially in acute brain slice preparations. We used [Ca(2+)]i imaging and patch clamp electrophysiology to decipher the mechanism of KA-evoked [Ca(2+)]i rise and its inhibition by the tricyclic antidepressant desipramine (DMI) in CA1 pyramidal cells in rat hippocampal slices and in cultured hippocampal cells. The effect of KA was dose-dependent and relied totally on extracellular Ca(2+). The lack of effect of dl-2-amino-5-phosphonopentanoic acid (AP-5) and abolishment of the response by 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) suggested the involvement of non-N-methyl-d-aspartate receptors (non-NMDARs). The predominant role of the Ca(2+)-impermeable α-amino-3-hydroxy-5-methyl-4-isoxazolepropionate receptors (AMPARs) in the initiation of the Ca(2+) response was supported by the inhibitory effect of the selective AMPAR antagonist GYKI 53655 and the ineffectiveness of 1-naphthyl acetylspermine (NASPM), an inhibitor of the Ca(2+)-permeable AMPARs. The voltage-gated Ca(2+) channels (VGCC), blocked by ω-Conotoxin MVIIC+nifedipine+NiCl2, contributed to the [Ca(2+)]i rise. VGCCs were also involved, similarly to AMPAR current, in the KA-evoked depolarisation. Inhibition of voltage-gated Na(+) channels (VGSCs; tetrodotoxin, TTX) did not affect the depolarisation of pyramidal cells but blocked the depolarisation-evoked action potential bursts and reduced the Ca(2+) response. The tricyclic antidepressant DMI inhibited the KA-evoked [Ca(2+)]i rise in a dose-dependent manner. It directly attenuated the AMPA-/KAR current, but its more potent inhibition on the Ca(2+) response supports additional effect on VGCCs, VGSCs and Na(+)/Ca(2+) exchangers. The multitarget action on decisive players of excitotoxicity holds out more promise in clinical therapy of neurodegenerative diseases. PMID:24742525

  1. Evidence for direct and indirect mechanisms in the potent modulatory action of interleukin-2 on the release of acetylcholine in rat hippocampal slices

    PubMed Central

    Seto, David; Kar, Satyabrata; Quirion, Rémi

    1997-01-01

    The biphasic nature of the potent modulatory action of interleukin-2 (IL-2) on hippocampal acetylcholine (ACh) release was investigated by use of brain slice superfusion.Both the potentiating (10−13 M) and inhibitory (10−9 M) effects of IL-2 on hippocampal ACh release were stimulation-dependent and were blocked by a neutralizing IL-2 receptor antibody, suggesting the activation of typical IL-2 receptors in both cases.Tetrodotoxin (TTX; 10 μM) failed to block the potentiation of ACh release induced by a very low concentration of IL-2 (10−13M) suggesting a direct effect on cholinergic nerve terminals.In contrast, the inhibitory effect seen at a higher concentration (10−9 M) was TTX-sensitive, and hence indicative of an indirect action.To establish the nature of this intermediate mediator, blockers of nitric oxide synthesis, and of opioid and γ-aminobutyric acid (GABA) receptors were used. Only GABAA and GABAB receptor antagonists altered the inhibitory action of IL-2, suggesting the participation of GABA as mediator.Taken together, these results provide further evidence for the potent role of IL-2 in the modulation of cholinergic function in the rat hippocampus. PMID:9134229

  2. Increased p38 mitogen-activated protein kinase signaling is involved in the oxidative stress associated with oxygen and glucose deprivation in neonatal hippocampal slice cultures

    PubMed Central

    Lu, Qing; Rau, Thomas F.; Harris, Valerie; Johnson, Maribeth; Poulsen, David J.; Black, Stephen M.

    2016-01-01

    The pathological basis of neonatal hypoxia–ischemia (HI) brain damage is characterized by neuronal cell loss. Oxidative stress is thought to be one of the main causes of HI-induced neuronal cell death. The p38 mitogen-activated protein kinase (MAPK) is activated under conditions of cell stress. However, its pathogenic role in regulating the oxidative stress associated with HI injury in the brain is not well understood. Thus, this study was conducted to examine the role of p38 MAPK signaling in neonatal HI brain injury using neonatal rat hippocampal slice cultures exposed to oxygen / glucose deprivation (OGD). Our results indicate that OGD led to a transient increase in p38 MAPK activation that preceded increases in superoxide generation and neuronal death. This increase in neuronal cell death correlated with an increase in the activation of caspase-3 and the appearance of apoptotic neuronal cells. Pre-treatment of slice cultures with the p38 MAPK inhibitor, SB203580, or the expression of an antisense p38 MAPK construct only in neuronal cells, through a Synapsin I-1-driven adeno-associated virus vector, inhibited p38 MAPK activity and exerted a neuroprotective effect as demonstrated by decreases in OGD-mediated oxidative stress, caspase activation and neuronal cell death. Thus, we conclude that the activation of p38 MAPK in neuronal cells plays a key role in the oxidative stress and neuronal cell death associated with OGD. PMID:21939459

  3. Electroosmotic Push–Pull Perfusion: Description and Application to Qualitative Analysis of the Hydrolysis of Exogenous Galanin in Organotypic Hippocampal Slice Cultures

    PubMed Central

    2013-01-01

    We demonstrate here a method that perfuses a small region of an organotypic hippocampal culture with a solution containing an enzyme substrate, a neuropeptide. Perfusate containing hydrolysis products is continually collected and subsequently analyzed for the products of the enzymatic degradation of the peptide substrate. The driving force for perfusion is an electric field. The fused silica capillaries used as “push” and “pull” or “source” and “collection” capillaries have a ζ-potential that is negative and greater in magnitude than the tissue’s ζ-potential. Thus, depending on the magnitudes of particular dimensions, the electroosmotic flow in the capillaries augments the fluid velocity in the tissue. The flow rate is not directly measured; however, we determine it using a finite-element approach. We have determined the collection efficiency of the system using an all d-amino acid internal standard. The flow rates are low, in the nL/min range, and adjustable by controlling the current or voltage in the system. The collection efficiency of the d-amino acid peptide internal standard is variable, increasing with increased current and thus electroosmotic flow rate. The collection efficiency can be rationalized in the context of a Peclet number. Electroosmotic push–pull perfusion of the neuropeptide galanin (gal1–29) through the extracellular space of an organotypic hippocampal culture results in its hydrolysis by ectopeptidase reactions occurring in the extracellular space. The products of hydrolysis were identified by MALDI-MS. Experiments at two levels of current (8–12 μA and 19–40 μA) show that the probability of seeing hydrolysis products (apparently from aminopeptidases) is greater in the Cornu Ammonis area 3 (CA3) than in the Cornu Ammonis area 1 (CA1) in the higher current experiments. In the lower current experiments, shorter peptide products of aminopeptidases (gal13–29 to gal20–19) are seen with greater frequency in CA3 than

  4. Pycnogenol protects CA3-CA1 synaptic function in a rat model of traumatic brain injury.

    PubMed

    Norris, Christopher M; Sompol, Pradoldej; Roberts, Kelly N; Ansari, Mubeen; Scheff, Stephen W

    2016-02-01

    Pycnogenol (PYC) is a patented mix of bioflavonoids with potent anti-oxidant and anti-inflammatory properties. Previously, we showed that PYC administration to rats within hours after a controlled cortical impact (CCI) injury significantly protects against the loss of several synaptic proteins in the hippocampus. Here, we investigated the effects of PYC on CA3-CA1 synaptic function following CCI. Adult Sprague-Dawley rats received an ipsilateral CCI injury followed 15 min later by intravenous injection of saline vehicle or PYC (10 mg/kg). Hippocampal slices from the injured (ipsilateral) and uninjured (contralateral) hemispheres were prepared at seven and fourteen days post-CCI for electrophysiological analyses of CA3-CA1 synaptic function and induction of long-term depression (LTD). Basal synaptic strength was impaired in slices from the ipsilateral, relative to the contralateral, hemisphere at seven days post-CCI and susceptibility to LTD was enhanced in the ipsilateral hemisphere at both post-injury timepoints. No interhemispheric differences in basal synaptic strength or LTD induction were observed in rats treated with PYC. The results show that PYC preserves synaptic function after CCI and provides further rationale for investigating the use of PYC as a therapeutic in humans suffering from neurotrauma. PMID:26607913

  5. Nondestructive evaluation of progressive neuronal changes in organotypic rat hippocampal slice cultures using ultrahigh-resolution optical coherence microscopy

    PubMed Central

    Li, Fengqiang; Song, Yu; Dryer, Alexandra; Cogguillo, William; Berdichevsky, Yevgeny; Zhou, Chao

    2014-01-01

    Abstract. Three-dimensional tissue cultures have been used as effective models for studying different diseases, including epilepsy. High-throughput, nondestructive techniques are essential for rapid assessment of disease-related processes, such as progressive cell death. An ultrahigh-resolution optical coherence microscopy (UHR-OCM) system with ∼1.5  μm axial resolution and ∼2.3  μm transverse resolution was developed to evaluate seizure-induced neuronal injury in organotypic rat hippocampal cultures. The capability of UHR-OCM to visualize cells in neural tissue was confirmed by comparison of UHR-OCM images with confocal immunostained images of the same cultures. In order to evaluate the progression of neuronal injury, UHR-OCM images were obtained from cultures on 7, 14, 21, and 28 days in vitro (DIVs). In comparison to DIV 7, statistically significant reductions in three-dimensional cell count and culture thickness from UHR-OCM images were observed on subsequent time points. In cultures treated with kynurenic acid, significantly less reduction in cell count and culture thickness was observed compared to the control specimens. These results demonstrate the capability of UHR-OCM to perform rapid, label-free, and nondestructive evaluation of neuronal death in organotypic hippocampal cultures. UHR-OCM, in combination with three-dimensional tissue cultures, can potentially prove to be a promising tool for high-throughput screening of drugs targeting various disorders. PMID:25750928

  6. Relationship between hippocampal atrophy and neuropathology markers: A 7T MRI validation study of the EADC-ADNI Harmonized Hippocampal Segmentation Protocol

    PubMed Central

    Apostolova, Liana G.; Zarow, Chris; Biado, Kristina; Hurtz, Sona; Boccardi, Marina; Somme, Johanne; Honarpisheh, Hedieh; Blanken, Anna E.; Brook, Jenny; Tung, Spencer; Lo, Darrick; Ng, Denise; Alger, Jeffry R.; Vinters, Harry V.; Bocchetta, Martina; Duvernoy, Henri; Jack, Clifford R.; Frisoni, Giovanni; Bartzokis, George; Csernansky, John G.; de Leon, Mony J.; deToledo-Morrell, Leyla; Killiany, Ronald J.; Lehéricy, Stéphane; Malykhin, Nikolai; Pantel, Johannes; Pruessner, Jens C.; Soininen, Hilkka; Watson, Craig

    2015-01-01

    Objective The pathologic validation of European Alzheimer's Disease Consortium Alzheimer's Disease Neuroimaging Center Harmonized Hippocampal Segmentation Protocol (HarP). Methods Temporal lobes of nine Alzheimer's disease (AD) and seven cognitively normal subjects were scanned post-mortem at 7 Tesla. Hippocampal volumes were obtained with HarP. Six-micrometer-thick hippocampal slices were stained for amyloid beta (Aβ), tau, and cresyl violet. Hippocampal subfields were manually traced. Neuronal counts, Aβ, and tau burden for each hippocampal subfield were obtained. Results We found significant correlations between hippocampal volume and Braak and Braak staging (ρ = −0.75, P = .001), tau (ρ = −0.53, P = .034), Aβ burden (ρ = −0.61, P = .012), and neuronal count (ρ = 0.77, P < .001). Exploratory subfield-wise significant associations were found for Aβ in CA1 (ρ = −0.58, P = .019) and subiculum (ρ = −0.75, P = .001), tau in CA2 (ρ = −0.59, P = .016), and CA3 (ρ = −0.5, P = .047), and neuronal count in CA1 (ρ = 0.55, P = .028), CA3 (ρ = 0.65, P = .006), and CA4 (ρ = 0.76, P = .001). Conclusions The observed associations provide the pathological confirmation of hippocampal morphometry as a valid biomarker for AD and the pathologic validation of HarP. PMID:25620800

  7. Recovery of Syrian hamster hippocampal signaling following its depression during oxygen-glucose deprivation is enhanced by cold temperatures and by hibernation.

    PubMed

    Mikhailova, Alexandra; Mack, Jacob; Vitagliano, Nicholas; Hamilton, Jock S; Horowitz, John M; Horwitz, Barbara A

    2016-05-16

    Signal transmission over a hippocampal network of CA3 and CA1 neurons in Syrian hamsters (Mesocricetus auratus), facultative hibernators, has not been fully characterized in response to oxygen-glucose deprivation (OGD). We hypothesized that during OGD, hippocampal signal transmission fails first at the synapse between CA3 and CA1 pyramidal neurons and that recovery of signal processing following OGD is more robust in hippocampal slices at cold temperature, from hamsters vs. rats, and from hibernating vs. non-hibernating hamsters. To test these hypotheses, we recorded fEPSPs and population spikes of CA1 neurons at 25°C, 30°C, and 35°C in 400μm slices over a 15min control period with the slice in oxygenated aCSF containing glucose (control solution), a 10min treatment period (OGD insult) where oxygen was replaced by nitrogen in aCSF lacking glucose, and a 30min recovery period with the slice in the control solution. The initial site of transmission failure during OGD occurred at the CA3-CA1 synapse, and recovery of signal transmission was at least, if not more (depending on temperature), complete in slices from hibernating vs. non-hibernating hamsters, and from non-hibernating hamsters vs. rats. Thus, hamster neuroprotective mechanisms supporting functional recovery were enhanced by cold temperatures and by hibernation. PMID:27068759

  8. Homeostatic and stimulus-induced coupling of the L-type Ca2+ channel to the ryanodine receptor in the hippocampal neuron in slices

    PubMed Central

    Berrout, Jonathan; Isokawa, Masako

    2009-01-01

    Activity-dependent increase in cytosolic calcium ([Ca2+]i) is a prerequisite for many neuronal functions. We previously reported a strong direct depolarization, independent of glutamate receptors, effectively caused a release of Ca2+ from ryanodine sensitive stores and induced the synthesis of endogenous cannabinoids (eCBs) and eCB-mediated responses. However, the cellular mechanism that initiated the depolarization-induced Ca2+ release is not completely understood. In the present study, we optically recorded [Ca2+]i from CA1 pyramidal neurons in the hippocampal slice and directly monitored miniature Ca2+ activities and depolarization-induced Ca2+ signals in order to determine the source(s) and properties of [Ca2+]i-dynamics that could lead to a release of Ca2+ from the ryanodine receptor. In the absence of depolarizing stimuli, spontaneously-occurring miniature Ca2+ events were detected from a group of hippocampal neurons. This miniature Ca2+ event persisted in the nominal Ca2+-containing artificial cerebrospinal fluid (ACSF), and increased in frequency in response to the bath-application of caffeine and KCl. In contrast, nimodipine, the antagonist of the L-type Ca2+ channel (LTCC), a high concentration of ryanodine, the antagonist of the ryanodine receptor (RyR), and thapsigargin (TG) reduced the occurrence of the miniature Ca2+ events. When a brief puff-application of KCl was given locally to the soma of individual neurons in the presence of glutamate receptor antagonists, these neurons generated a transient increase in the [Ca2+]i in the dendrosomal region. This [Ca2+]i-transient was sensitive to nimodipine, TG, and ryanodine suggesting that the [Ca2+]i-transient was caused primarily by the LTCC-mediated Ca2+-influx and a release of Ca2+ from RyR. We observed little contribution from N-or P/Q-type Ca2+ channels. The coupling between LTCC and RyR was direct and independent of synaptic activities. Immunohistochemical study revealed a cellular localization of LTCC

  9. Visualization of the spread of electrical activity in rat hippocampal slices by voltage-sensitive optical probes

    PubMed Central

    Grinvald, A.; Manker, A.; Segal, M.

    1982-01-01

    1. Voltage-sensitive membrane-bound dyes and a matrix of 100 photodetectors were used to detect the spread of evoked electrical activity at the CA1 region of rat hippocampus slices. A display processor was designed in order to visualize the spread of electrical activity in slow motion. 2. The stimulation of the Schaffer collateral-commissural path in the stratum radiatum evoked short latency (2-4 msec) fast optical signals, followed by longer latency (4-15 msec) slow signals which decayed within 20-50 msec. Multiple fast signals were frequently detected at the stratum pyramidale; they propagated toward the stratum oriens with an approximate conduction velocity of 0.1 m/sec. 3. The fast signals were unaltered in a low Ca2+ high Mg2+ medium but were blocked by tetrodotoxin. These signals probably represent action potentials in the Schaffer collateral axons. Their conduction velocity was about 0.2 m/sec and their refractory period about 3-4 msec. 4. The slow signals were absent in a low Ca2+ medium and probably represent excitatory post-synaptic potentials (e.p.s.p.s) generated in the apical dendrites of the pyramidal cells. They were generated in the stratum radiatum, where the presynaptic signals were seen, and spread into somata and basal dendrites (the stratum pyramidale and oriens, respectively). 5. The timing of the signals with fast rise-time, which were detected at the statum pyramidale, approximately coincided with the timing of the extracellularly recorded field potentials. These multiple discharges probably represent action potentials of the pyramidal cells. They spread back into the apical dendrites but with significant attenuation of the amplitudes of the high frequency components of the pyramidal action potentials. 6. Hyperpolarizing potentials could be detected when strong stimuli were applied to the stratum radiatum or alveus. The net hyperpolarizations were detected only in the stratum pyramidale and the border region between the stratum pyramidale

  10. Aerobic Production and Utilization of Lactate Satisfy Increased Energy Demands Upon Neuronal Activation in Hippocampal Slices and Provide Neuroprotection Against Oxidative Stress

    PubMed Central

    Schurr, Avital; Gozal, Evelyne

    2012-01-01

    Ever since it was shown for the first time that lactate can support neuronal function in vitro as a sole oxidative energy substrate, investigators in the field of neuroenergetics have been debating the role, if any, of this glycolytic product in cerebral energy metabolism. Our experiments employed the rat hippocampal slice preparation with electrophysiological and biochemical methodologies. The data generated by these experiments (a) support the hypothesis that lactate, not pyruvate, is the end-product of cerebral aerobic glycolysis; (b) indicate that lactate plays a major and crucial role in affording neural tissue to respond adequately to glutamate excitation and to recover unscathed post-excitation; (c) suggest that neural tissue activation is accompanied by aerobic lactate and NADH production, the latter being produced when the former is converted to pyruvate by mitochondrial lactate dehydrogenase (mLDH); (d) imply that NADH can be utilized as an endogenous scavenger of reactive oxygen species (ROS) to provide neuroprotection against ROS-induced neuronal damage. PMID:22275901

  11. Electroosmotic perfusion of tissue: sampling the extracellular space and quantitative assessment of membrane-bound enzyme activity in organotypic hippocampal slice cultures

    PubMed Central

    Ou, Yangguang; Wu, Juanfang; Sandberg, Mats

    2014-01-01

    This review covers recent advances in sampling fluid from the extracellular space of brain tissue by electroosmosis (EO). Two techniques, EO sampling with a single fused-silica capillary and EO push–pull perfusion, have been developed. These tools were used to investigate the function of membrane-bound enzymes with outward-facing active sites, or ectoenzymes, in modulating the activity of the neuropeptides leu-enkephalin and galanin in organotypic-hippocampal-slice cultures (OHSCs). In addition, the approach was used to determine the endogenous concentration of a thiol, cysteamine, in OHSCs. We have also investigated the degradation of coenzyme A in the extracellular space. The approach provides information on ectoenzyme activity, including Michaelis constants, in tissue, which, as far as we are aware, has not been done before. On the basis of computational evidence, EO push–pull perfusion can distinguish ectoenzyme activity with a ~100 µm spatial resolution, which is important for studies of enzyme kinetics in adjacent regions of the rat hippocampus. PMID:25168111

  12. Effect of Rubia cordifolia, Fagonia cretica linn, and Tinospora cordifolia on free radical generation and lipid peroxidation during oxygen-glucose deprivation in rat hippocampal slices.

    PubMed

    Rawal, Avinash; Muddeshwar, Manohar; Biswas, Saibal

    2004-11-12

    The major damaging factor during and after the ischemic/hypoxic insult is the generation of free radicals, which leads to apoptosis, necrosis, and ultimately cell death. Rubia cordifolia (RC), Fagonia cretica linn (FC), and Tinospora cordifolia (TC) have been reported to contain a wide variety of antioxidants and have been in use in the eastern system of medicine for various disorders. Hippocampal slices were subjected to oxygen-glucose deprivation (OGD) and divided into three groups, control, OGD, and OGD+drug treated. Cytosolic reduced glutathione (GSH), nitric oxide [NO, measured as nitrite (NO2)]. EPR was used to establish the antioxidant effect of RC, FC, and TC with respect to superoxide anion (O*2-), hydroxyl radicals (*OH), nitric oxide (NO) radical, and peroxynitrite anion (ONOO-) generated from pyrogallol, menadione, DETA-NO, and Sin-1, respectively. RT-PCR was performed for the three herbs to assess their effect on the expression of gamma-glutamylcysteine ligase (GCLC), iNOS, and GAPDH gene expression. All the three herbs were effective in elevating the GSH levels and expression of the GCLC. The herbs also exhibited strong free radical scavenging properties against reactive oxygen and nitrogen species as revealed by electron paramagnetic resonance spectroscopy, diminishing the expression of iNOS gene. RC, FC, and TC therefore attenuate oxidative stress mediated cell injury during OGD and exert the above effects at both the cytosolic as well as at gene expression levels and may be effective therapeutic tool against ischemic brain damage. PMID:15474468

  13. Photolytically released nitric oxide produces a delayed but persistent suppression of LTP in area CA1 of the rat hippocampal slice

    PubMed Central

    Murphy, K P S J; Bliss, T V P

    1999-01-01

    We have used flash photolysis of a caged form of nitric oxide (NO), potassium pentachloronitrosylruthenate (K2Ru(NO)Cl5), to apply known concentrations of NO, with a high degree of temporal resolution, to hippocampal slices prepared from juvenile male rats maintained in an interface recording chamber. Photolytically released NO (1–4.5 μM) from bath applied caged NO reduced the magnitude of long-term potentiation (LTP) in a concentration-dependent manner. This effect was abolished in the presence of the NO scavenger haemoglobin. NO had no effect on pre-established LTP. Exposure to photolytically released NO had no effect on normal fast synaptic transmission, but did result in depression of N-methyl-D-aspartate (NMDA) receptor-mediated transmission recorded using extracellular electrodes. The onset of NO-induced depression was relatively slow, taking >40 s to manifest itself, and several minutes to achieve maximum depression (t½≈ 70 s). NO-induced depression persisted for more than 2 h after photolysis. The time courses of the action of NO on NMDA receptor-mediated responses and its action on the induction of LTP were similar. These results suggest that released NO may play a role in determining the subsequent threshold for the induction of LTP at Schaffer-commissural synapses through a reduction in the efficacy of NMDA receptor function when repeated conditioning trains are used. PMID:10050012

  14. Synaptic Proteins In Schizophrenia Hippocampus Indicate Increased Neuronal Activity in CA3

    PubMed Central

    Li, Wei; Ghose, Subroto; Gleason, Kelly; Begovic’, Anita; Perez, Jessica; Bartko, John; Russo, Scott; Wagner, Anthony D.; Selemon, Lynn; Tamminga, Carol A.

    2015-01-01

    In schizophrenia, hippocampal perfusion is increased and declarative memory function is degraded. Based on a model of hippocampal dysfunction in schizophrenic psychosis, we postulated increased NMDA receptor signaling in CA3. Here we demonstrate that the GluN2B-containing NMDA receptors (GluN2B/GluN1) and its associated postsynaptic membrane protein PSD95 are both increased in human hippocampal CA3 from schizophrenia cases, but not in CA1 tissue. Quantitative analyses of Golgi-stained hippocampal neurons show an increase in spine density on CA3 pyramidal cell apical dendrites (stratum radiatum) and an increase in the number of thorny excrescences. AMPA receptor subunit proteins are not altered in CA3 or CA1 subfields, nor are several additional related signaling proteins. These hippocampal data are consistent with increased excitatory signaling in CA3 and/or with an elevation in silent synapses in CA3, a state which may contribute to development of long term potentiation with subsequent stimulation and ‘un-silencing’. These changes are plausibly associated with increased associational activity in CA3, degraded declarative memory function and with psychotic manifestations in schizophrenia. The influence of these hyperactive hippocampal projections onto targets in limbic neocortex could contribute to components of schizophrenia manifestations in other cerebral regions. PMID:25585032

  15. Slice orientation and muscarinic acetylcholine receptor activation determine the involvement of N-methyl D-aspartate receptor subunit GluN2B in hippocampal area CA1 long-term depression

    PubMed Central

    2011-01-01

    Background The contribution of different GluN2 subunits of the N-methyl D-aspartate (NMDA) receptor to the induction of bidirectional hippocampal synaptic plasticity is a controversial topic. As both supporting and refuting evidence for the hypothesis of subunit specialization in opposing directions of plasticity has accumulated since it was first proposed a few years ago, we hypothesize that differences in experimental conditions may have in part contributed to some of the inconsistent results from these studies. Here we investigate the controversial hypothesis that long-term depression (LTD) is preferentially induced by GluN2B-containing NMDA receptors in area CA1 of hippocampal slices. Results We find that brain slices from 2-3 week old rats prepared in the sagittal orientation have GluN2B-independent LTD whereas slices prepared in the coronal orientation have GluN2B-dependent LTD. There was no difference between the orientations in the fraction of the NMDAR EPSC sensitive to a GluN2B-selective antagonist, leading us to believe that the intracellular signaling properties of the NMDARs were different in the two preparations. Coronal slices had greater association of LTD-related intracellular signaling protein RasGRF1 with GluN2B relative to sagittal slices. Antagonism of muscarinic acetylcholine receptors (mAChRs) in the sagittal slices returned LTD to a GluN2B-dependent form and increased the association of GluN2B with RasGRF1. Conclusions These results suggest a novel form of NMDAR modulation by mAChRs and clarify some disagreement in the literature. PMID:22082088

  16. A comparison of distal and proximal dendritic synapses on CA1 pyramids in guinea-pig hippocampal slices in vitro

    PubMed Central

    Andersen, P.; Silfvenius, H.; Sundberg, S. H.; Sveen, O.

    1980-01-01

    1. In vitro slices of guinea-pig hippocampus have been employed to compare excitatory synapses located distally and proximally on the dendritic tree of CA1 pyramidal cells. 2. The main orientation of unmyelinated afferent fibres was found to be parallel to each other and perpendicular to the dendritic axis. 3. The density of boutons ending on dendritic spines was roughly similar throughout the greater part of the dendritic tree with an average of 42 ± 7·2 synapses per 100 μm2. Their number did, however, decrease in the distal fifth of the apical and in the distal third of the basal dendritic region in parallel with an increase of boutons on the dendritic shafts. 4. Negative synaptic field potentials (extracellular field e.p.s.p.s) had their maximum in the region where activated afferent fibres terminated and showed reversal when recorded from sufficiently displaced positions along the dendritic axis. The field e.p.s.p. was preceded by a diphasic presynaptic fibre volley. By cutting all but a narrow bundle of afferent fibres selective activation of a small group of dendritic synapses was possible. Stimulation of fibres crossing tissue bridges (35-100 μm wide) evoked field e.p.s.p.s comparable in amplitude to those seen in slices without lesions. The size of the field e.p.s.p.s evoked via distal and proximal bridges was remarkably similar and linearly related to the size of the appropriate stimulus current and presynaptic volley. 5. Selective activation of a small group of afferent fibres gave rise to large amplitude population spikes. Proximal and distal bridges were largely equipotent when they were equally wide. Above the threshold amplitude, the evoked population spikes were linearly related to both the presynaptic volley and the stimulus current. Constant current stimulation of fibres at all apical dendritic levels was equally effective in evoking population spikes, with the exception of the outer fifth of the tree where stimulation was unsuccessful. Input

  17. CA1 Long-Term Potentiation Is Diminished but Present in Hippocampal Slices from α-CaMKII Mutant Mice

    PubMed Central

    Hinds, Heather L.; Tonegawa, Susumu; Malinow, Roberto

    1998-01-01

    Previous work has shown that mice missing the α-isoform of calcium–calmodulin-dependent protein kinase II (α-CaMKII) have a deficiency in CA1 hippocampal long-term potentiation (LTP). Follow-up studies on subsequent generations of these mutant mice in a novel inbred background by our laboratories have shown that whereas a deficiency in CA1 LTP is still present in α-CaMKII mutant mice, it is different both quantitatively and qualitatively from the deficiency first described. Mice of a mixed 129SvOla/SvJ;BALB/c;C57Bl/6 background derived from brother/sister mating of the α-CaMKII mutant line through multiple generations (>10) were produced by use of in vitro fertilization. Although LTP at 60 min post-tetanus was clearly deficient in these (−/−) α-CaMKII mice (42.6%, n = 33) compared with (+/+) α-CaMKII control animals (81.7%, n = 17), α-CaMKII mutant mice did show a significant level of LTP. The amount of LTP observed in α-CaMKII mutants was normally distributed, blocked by APV (2.7%, n = 8), and did not correlate with age. Although this supports a role for α-CaMKII in CA1 LTP, it also suggests that a form of α-CaMKII-independent LTP is present in mice that could be dependent on another kinase, such as the β-isoform of CaMKII. A significant difference in input/output curves was also observed between (−/−) α-CaMKII and (+/+) α-CaMKII animals, suggesting that differences in synaptic transmission may be contributing to the LTP deficit in mutant mice. However, tetani of increasing frequency (50, 100, and 200 Hz) did not reveal a higher threshold for potentiation in (−/−) α-CaMKII mice compared with (+/+) α-CaMKII controls. PMID:10454359

  18. An in situ Measurement of Extracellular Cysteamine, Homocysteine and Cysteine Concentrations in Organotypic Hippocampal Slice Cultures by Integration of Electroosmotic Sampling and Microfluidic Analysis

    PubMed Central

    Wu, Juanfang; Xu, Kerui; Landers, James P.; Weber, Stephen G.

    2013-01-01

    We demonstrate an all-electric sampling/derivatization/separation/detection system for the quantitation of thiols in tissue cultures. Extracellular fluid collected from rat organotypic hippocampal slice cultures (OHSCs) by electroosmotic flow through an11 cm (length) × 50 μm (ID) sampling capillary is introduced to a simple microfluidic chip for derivatization, continuous flow-gated injection, separation and detection.With the help of a fluorogenic, thiol-specific reagent, ThioGlo-1, we have successfully separated and detected the extracellular levels of free reduced cysteamine, homocysteineand cysteinefrom OHSCs within 25 s in a 23 mm separation channel with a confocal laser induced fluorescence (LIF) detector. Attention to the conductivities of the fluids being transported is required for successful flow-gated injections.When the sample conductivity is much higher than the run buffer conductivities, the electroosmotic velocities are such that there is less fluid coming by electroosmosis into the cross from the sample/reagent channel than is leaving by electroosmosis into the separation and waste channels. The resulting decrease in the internal fluid pressure in the injection cross pulls flow from the gated channel. This process may completely shut down the gated injection. Using a glycylglycine buffer with physiological osmolarity but only 62% of physiological conductivity and augmenting the conductivity of the run buffers solved this problem. Quantitation is by standard additions. Concentrations of cysteamine, homocysteine and cysteine in the extracellular space of OHSCs are10.6±1.0 nM (n=70), 0.18±0.01 μM (n=53) and 11.1±1.2 μM (n=70), respectively. This is the first in situquantitative estimation of endogenous cysteamine in brain. Extracellular levels of homocysteine and cysteine are comparable with other reported values. PMID:23330713

  19. Neuroprotection by JM-20 against oxygen-glucose deprivation in rat hippocampal slices: Involvement of the Akt/GSK-3β pathway.

    PubMed

    Ramírez-Sánchez, Jeney; Simões Pires, Elisa Nicoloso; Nuñez-Figueredo, Yanier; Pardo-Andreu, Gilberto L; Fonseca-Fonseca, Luis Arturo; Ruiz-Reyes, Alberto; Ochoa-Rodríguez, Estael; Verdecia-Reyes, Yamila; Delgado-Hernández, René; Souza, Diogo O; Salbego, Christianne

    2015-11-01

    Cerebral ischemia is the third most common cause of death and a major cause of disability worldwide. Beyond a shortage of essential metabolites, ischemia triggers many interconnected pathophysiological events, including excitotoxicity, oxidative stress, inflammation and apoptosis. Here, we investigated the neuroprotective mechanisms of JM-20, a novel synthetic molecule, focusing on the phosphoinositide-3-kinase (PI3K)/Akt survival pathway and glial cell response as potential targets of JM-20. For this purpose, we used organotypic hippocampal slice cultures exposed to oxygen-glucose deprivation (OGD) to achieve ischemic/reperfusion damage in vitro. Treatment with JM-20 at 0.1 and 10 μM reduced PI incorporation (indicative of cell death) after OGD. OGD decreased the phosphorylation of Akt (pro-survival) and GSK 3β (pro-apoptotic), resulting in respective inhibition and activation of these proteins. Treatment with JM20 prevented the reduced phosphorylation of these proteins after OGD, representing a shift from pro-apoptotic to pro-survival signaling. The OGD-induced activation of caspase-3 was also attenuated by JM-20 treatment at 10 μM. Moreover, in cultures treated with JM-20 and exposed to OGD conditioning, we observed a decrease in activated microglia, as well as a decrease in interleukin (IL)-1β, IL-6 and tumor necrosis factor (TNF)-α release into the culture medium, while the level of the anti-inflammatory IL-10 increased. GFAP immunostaining and IB4 labeling showed that JM-20 treatment significantly augmented GFAP immunoreactivity after OGD, when compared with cultures exposed to OGD only, suggesting the activation of astroglial cells. Our results confirm that JM-20 has a strong neuroprotective effect against ischemic injury and suggest that the mechanisms involved in this effect may include the modulation of reactive astrogliosis, as well as neuroinflammation and the anti-apoptotic cell signaling pathway. PMID:26361722

  20. Effects of enoxacin and its combination with 4-biphenylacetate, an active metabolite of fenbufen, on population spikes in rat hippocampal slices.

    PubMed

    Ito, T; Miura, Y; Kadokawa, T; Hori, S; Shimada, J; Miyahara, T

    1991-03-01

    The effects of enoxacin, a new quinolone antibacterial agent, and its combination with 4-biphenylacetate (BPA), an active metabolite of the non-steroidal antiinflammatory agent fenbufen, were examined on population spikes induced by electrical stimulation of the stratum radiatum in the CA1 pyramidal cell layer in rat hippocampal slices. Enoxacin (10(-4) M) and bicuculline (10(-6) M) increased the amplitude of the population spikes and anew elicited the second spikes (latency: 10 msec.), while BPA (10(-5) M) decreased the amplitude of the population spikes. However, the combination of enoxacin (10(-6), 10(-5) M) with BPA (10(-5) M) elicited the second spikes or epileptiform bursts with an increase of the population spike amplitude. The dose-response relationships showed that the effect of enoxacin was 100 times potentiated in the presence of BPA (10(-5) M). The second spikes induced by enoxacin (10(-4) M) were suppressed by muscimol (10(-6) M) and baclofen (10(-6) M), but not by clorazepate (5 x 10(-5) M) and pentobarbital (5 x 10(-5) M). The second spikes induced by bicuculline (10(-6) M) were suppressed by these four drugs. The second spikes by the combination of enoxacin (10(-6) M) with BPA (10(-5) M) were suppressed by muscimol (5 x 10(-6) M), but not by clorazepate (5 x 10(-5) M). These results suggest that the combination of enoxacin with BPA exerts a drug interaction to elicit the second spikes or epileptiform bursts with its mode of action different from that of bicuculline. PMID:2057453

  1. Cannabinoids and neuronal damage: differential effects of THC, AEA and 2-AG on activated microglial cells and degenerating neurons in excitotoxically lesioned rat organotypic hippocampal slice cultures.

    PubMed

    Kreutz, Susanne; Koch, Marco; Ghadban, Chalid; Korf, Horst-Werner; Dehghani, Faramarz

    2007-01-01

    Cannabinoids (CBs) are attributed neuroprotective effects in vivo. Here, we determined the neuroprotective potential of CBs during neuronal damage in excitotoxically lesioned organotypic hippocampal slice cultures (OHSCs). OHSCs are the best characterized in vitro model to investigate the function of microglial cells in neuronal damage since blood-borne monocytes and T-lymphocytes are absent and microglial cells represent the only immunocompetent cell type. Excitotoxic neuronal damage was induced by NMDA (50 microM) application for 4 h. Neuroprotective properties of 9-carboxy-11-nor-delta-9-tetrahydrocannabinol (THC), N-arachidonoylethanolamide (AEA) or 2-arachidonoylglycerol (2-AG) in different concentrations were determined after co-application with NMDA by counting degenerating neurons identified by propidium iodide labeling (PI(+)) and microglial cells labeled by isolectin B(4) (IB(4)(+)). All three CBs used significantly decreased the number of IB(4)(+) microglial cells in the dentate gyrus but the number of PI(+) neurons was reduced only after 2-AG treatment. Application of AM630, antagonizing CB2 receptors highly expressed by activated microglial cells, did not counteract neuroprotective effects of 2-AG, but affected THC-mediated reduction of IB(4)(+) microglial cells. Our results indicate that (1) only 2-AG exerts neuroprotective effects in OHSCs; (2) reduction of IB(4)(+) microglial cells is not a neuroprotective event per se and involves other CB receptors than the CB2 receptor; (3) the discrepancy in the neuroprotective effects of CBs observed in vivo and in our in vitro model system may underline the functional relevance of invading monocytes and T-lymphocytes that are absent in OHSCs. PMID:17010339

  2. Evaluation of Mitochondrial Function in the CNS of Rodent Models of Alzheimer's Disease - High Resolution Respirometry Applied to Acute Hippocampal Slices.

    PubMed

    Dias, Candida; Barbosa, Rui M; Laranjinha, Joao; Ledo, Ana

    2014-10-01

    Alzheimer's disease (AD) is a multifactorial disease characterized by extracellular deposits of amyloid plaques and intracellular neurofibrillary tangles. These hallmark alterations are preceded by synaptic deterioration, changes in neuromolecular plasticity phenomena, mitochondrial dysfunction, increase in oxidative damage to cellular constituents and decreased energy metabolism. The hippocampus is a structure of the temporal medial lobe implicated in specific forms of memory processes. It is also one of the first and most affected regions of the CNS in AD. Here we present a novel approach to the study if mitochondrial function/disfunction in 2 rodent models of AD: an acute rat model obtained by intracerebroventricular injection of the toxin streptozotocin (STZ) and a progressive triple transgenic mouse model (3TgAD) harboring PS1M146V, APPSwe, and tauP301L transgenes. Mitochondrial dysfunction has classically been assessed in such models by isolating mitochondria, synaptossoms or working with cell cultures. Anyone of these approaches destroys the intricate intercellular connectivity and cytoarchitecture of neuronal tissue. We used acute hippocampal slices obtained from the 2 models of AD and evaluated changes in mitochondrial function as a function of disease and/or age. Mitochondrial stress test were performed on the high resolution respirometry (Oroboros 2K Oxymeter). Upon analysis of oxygen consumption rates (OCR) we observed significant decreases in basal OCR, maximal respiratory capacity, ATP turnover and a tendency for decrease in sparing capacity in the STZ rat model compared to shame injected animals. Regarding the 3TgAD model we observed an age-dependent decrease in all parameters evaluated in the mitochondrial stress test, in both 3TgAD and NTg animals. However, although a tendency towards decreased OCR was observed when comparing 3TgAD and age-matched NTg animals, no statistically significant difference was observed. PMID:26461355

  3. Effects of sex steroid hormones and their metabolites on neuronal injury caused by oxygen-glucose deprivation/reoxygenation in organotypic hippocampal slice cultures.

    PubMed

    Ishihara, Yasuhiro; Fujitani, Noriko; Sakurai, Hikaru; Takemoto, Takuya; Ikeda-Ishihara, Nami; Mori-Yasumoto, Kanami; Nehira, Tatsuo; Ishida, Atsuhiko; Yamazaki, Takeshi

    2016-09-01

    In this study, protective actions of the sex steroid hormones, progesterone, testosterone, and 17β-estradiol, against oxygen-glucose deprivation (OGD)/reoxygenation-induced neuronal cell death were examined using rat organotypic hippocampal slice cultures. Progesterone, testosterone, and 17β-estradiol significantly attenuated neuronal cell death elicited by OGD/reoxygenation. While the neuroprotection conferred by progesterone was not affected by SU-10603, an inhibitor of cytochrome P45017α, finasteride, a 5α-reductase inhibitor that blocks the conversion of progesterone to allopregnanolone, partially reversed the neuroprotection induced by progesterone. The progesterone metabolite, allopregnanolone attenuated neuronal injury induced by OGD/reoxygenation. Pretreatment with letrozole, a cytochrome P450 aromatase inhibitor or 4-hydroxyphenyl-1-naphthol, a 17β-hydroxysteroid dehydrogenase 2 inhibitor showed no effect on testosterone-mediated neuroprotection, while finasteride completely abolished the protective action of testosterone. Treatment with 5α-dihydrotestosterone significantly suppressed neuronal injury. Pretreatment with mifepristone, a progesterone receptor antagonist and hydroxyflutamid, an androgen receptor antagonist significantly diminished the neuroprotective effects of progesterone and testosterone, respectively. ICI182,780, an estrogen receptor antagonist, showed no effect on neuroprotection mediated by 17β-estradiol. Pretreatment with actinomycin D or cycloheximide clearly abolished the neuroprotective effects of progesterone and testosterone, while actinomycin D and cycloheximide did not show any effect on neuroprotection mediated by 17β-estradiol. Taken together, progesterone protects neurons via progesterone receptor-dependent genomic pathway, and allopregnanolone is involved in progesterone-mediated neuroprotection. Testosterone and its metabolite 5α-dihydrotestosterone protect neurons via the genomic pathway of the androgen receptor

  4. Methylxanthine-evoked perturbation of spontaneous and evoked activities in isolated newborn rat hippocampal networks.

    PubMed

    Ruangkittisakul, A; Sharopov, S; Kantor, C; Kuribayashi, J; Mildenberger, E; Luhmann, H J; Kilb, W; Ballanyi, K

    2015-08-20

    Treatment of apnea of prematurity with methylxanthines like caffeine, aminophylline or theophylline can evoke hippocampal seizures. However, it is unknown at which interstitial brain concentrations methylxanthines promote such neonatal seizures or interfere with physiological 'early network oscillations' (ENOs) that are considered as pivotal for maturation of hippocampal neural networks. We studied theophylline and caffeine effects on ENOs in CA3 neurons (CA3-ENOs) and CA3 electrical stimulation-evoked monosynaptic CA1 field potentials (CA1-FPs) in sliced and intact hippocampi, respectively, from 8 to 10-days-old rats. Submillimolar doses of theophylline and caffeine, blocking adenosine receptors and phosphodiesterase-4 (PDE4), did not affect CA3-ENOs, ENO-associated cytosolic Ca(2+) transients or CA1-FPs nor did they provoke seizure-like discharges. Low millimolar doses of theophylline (⩾1mM) or caffeine (⩾5mM), blocking GABAA and glycine receptors plus sarcoplasmic-endoplasmic reticulum Ca(2+) ATPase (SERCA)-type Ca(2+) ATPases, evoked seizure-like discharges with no indication of cytosolic Ca(2+) dysregulation. Inhibiting PDE4 with rolipram or glycine receptors with strychnine had no effect on CA3-ENOs and did not occlude seizure-like events as tested with theophylline. GABAA receptor blockade induced seizure-like discharges and occluded theophylline-evoked seizure-like discharges in the slices, but not in the intact hippocampi. In summary, submillimolar methylxanthine concentrations do not acutely affect spontaneous CA3-ENOs or electrically evoked synaptic activities and low millimolar doses are needed to evoke seizure-like discharges in isolated developing hippocampal neural networks. We conclude that mechanisms of methylxanthine-related seizure-like discharges do not involve SERCA inhibition-related neuronal Ca(2+) dysregulation, PDE4 blockade or adenosine and glycine receptor inhibition, whereas GABA(A) receptor blockade may contribute partially. PMID

  5. Distinct Roles for Dorsal CA3 and CA1 in Memory for Sequential Nonspatial Events

    ERIC Educational Resources Information Center

    Farovik, Anja; Dupont, Laura M.; Eichenbaum, Howard

    2010-01-01

    Previous studies have suggested that dorsal hippocampal areas CA3 and CA1 are both involved in representing sequences of events that compose unique episodes. However, it is uncertain whether the contribution of CA3 is restricted to spatial information, and it is unclear whether CA1 encodes order per se or contributes by an active maintenance of…

  6. Pattern Separation, Pattern Completion, and New Neuronal Codes within a Continuous CA3 Map

    ERIC Educational Resources Information Center

    Leutgeb, Stefan; Leutgeb, Jill K.

    2007-01-01

    The hippocampal CA3 subregion is critical for rapidly encoding new memories, which suggests that neuronal computations are implemented in its circuitry that cannot be performed elsewhere in the hippocampus or in the neocortex. Recording studies show that CA3 cells are bound to a large degree to a spatial coordinate system, while CA1 cells can…

  7. TRPV1 receptors augment basal synaptic transmission in CA1 and CA3 pyramidal neurons in epilepsy.

    PubMed

    Saffarzadeh, F; Eslamizade, M J; Mousavi, S M M; Abraki, S B; Hadjighassem, M R; Gorji, A

    2016-02-01

    Temporal lobe epilepsy in human and animals is attributed to alterations in brain function especially hippocampus formation. Changes in synaptic activity might be causally related to the alterations during epileptogenesis. Transient receptor potential vanilloid 1 (TRPV1) as one of the non-selective ion channels has been shown to be involved in synaptic transmission. However, the potential role of TRPV1 receptors in synaptic function in the epileptic brain needs to be elucidated. In the present study, we used quantitative real-time PCR (qRT-PCR), western blotting, and immunohistochemistry to assess hippocampal TRPV1 mRNA expression, protein content, and distribution. Moreover, the effects of pharmacologic activation and inhibition of TRPV1 receptors on the slope of evoked field excitatory postsynaptic potentials (fEPSPs) were analyzed in CA1 and CA3 pyramidal neurons, after 3months of pilocarpine-induced status epilepticus (SE). SE induced an upregulation of TRPV1 mRNA and protein content in the whole hippocampal extract, as well as its distribution in both CA1 and CA3 regions. Activation and inhibition of TRPV1 receptors (via capsaicin 1μM and capsazepine 10μM, respectively) did not influence basal synaptic transmission in CA1 and CA3 regions of control slices, however, capsaicin increased and capsazepine decreased synaptic transmission in both regions in tissues from epileptic animals. Taken together, these findings suggest that a higher expression of TRPV1 in the epileptic condition is accompanied by alterations in basal synaptic transmission. PMID:26621124

  8. Relative contributions of CA3 and medial entorhinal cortex to memory in rats

    PubMed Central

    O'Reilly, Kally C.; Alarcon, Juan M.; Ferbinteanu, Janina

    2014-01-01

    The hippocampal CA1 field processes spatial information, but the relative importance of intra- vs. extra-hippocampal sources of input into CA1 for spatial behavior is unclear. To characterize the relative roles of these two sources of input, originating in the hippocampal field CA3 and in the medial entorhinal cortex (MEC), we studied effects of discrete neurotoxic lesions of CA3 or MEC on concurrent spatial and nonspatial navigation tasks, and on synaptic transmission in afferents to CA1. Lesions in CA3 or MEC regions that abolished CA3-CA1, or reduced MEC-CA1 synaptic transmission, respectively, impaired spatial navigation and unexpectedly interfered with cue response, suggesting that in certain conditions of training regimen, hippocampal activity may influence behavior otherwise supported by nonhippocampal neural networks. MEC lesions had milder and temporary behavioral effects, but also markedly amplified transmission in the CA3-CA1 pathway. Extensive behavioral training had a similar, but more modest effect on CA3-CA1 transmission. Thus, cortical input to the hippocampus modulates CA1 activity both directly and indirectly, through heterosynaptic interaction, to control information flow in the hippocampal loop. Following damage to hippocampal cortical input, the functional coupling of separate intra- and extra-hippocampal inputs to CA1 involved in normal learning may initiate processes that support recovery of behavioral function. Such a process may explain how CA3 lesions, which do not significantly modify the basic features of CA1 neural activity, nonetheless impair spatial recall, whereas lesions of EC input to CA1, which reduce the spatial selectivity of CA1 firing in foraging rats, have only mild effects on spatial navigation. PMID:25221487

  9. Symmetric spike timing-dependent plasticity at CA3-CA3 synapses optimizes storage and recall in autoassociative networks.

    PubMed

    Mishra, Rajiv K; Kim, Sooyun; Guzman, Segundo J; Jonas, Peter

    2016-01-01

    CA3-CA3 recurrent excitatory synapses are thought to play a key role in memory storage and pattern completion. Whether the plasticity properties of these synapses are consistent with their proposed network functions remains unclear. Here, we examine the properties of spike timing-dependent plasticity (STDP) at CA3-CA3 synapses. Low-frequency pairing of excitatory postsynaptic potentials (EPSPs) and action potentials (APs) induces long-term potentiation (LTP), independent of temporal order. The STDP curve is symmetric and broad (half-width ∼150 ms). Consistent with these STDP induction properties, AP-EPSP sequences lead to supralinear summation of spine [Ca(2+)] transients. Furthermore, afterdepolarizations (ADPs) following APs efficiently propagate into dendrites of CA3 pyramidal neurons, and EPSPs summate with dendritic ADPs. In autoassociative network models, storage and recall are more robust with symmetric than with asymmetric STDP rules. Thus, a specialized STDP induction rule allows reliable storage and recall of information in the hippocampal CA3 network. PMID:27174042

  10. Pharmacological antagonism of the actions of group II and III mGluR agonists in the lateral perforant path of rat hippocampal slices.

    PubMed

    Bushell, T J; Jane, D E; Tse, H W; Watkins, J C; Garthwaite, J; Collingridge, G L

    1996-04-01

    1. An understanding of the physiological and pathological roles of metabotropic glutamate receptors (mGluRs) is currently hampered by the lack of selective antagonists. Standard extracellular recording techniques were used to investigate the activity of recently reported mGluR antagonists on agonist-induced depressions of synaptic transmission in the lateral perforant path of hippocampal slices obtained from 12-16 day-old rats. 2. The group III specific mGluR agonist, (S)-2-amino-4-phosphonobutanoate (L-AP4) depressed basal synaptic transmission in a reversible and dose-dependent manner. The mean (+/-s.e. mean) depression obtained with 100 microM L-AP4 (the maximum concentration tested) was 74 +/- 3% and the IC50 value was 3 +/- 1 microM (n = 5). 3. The selective group II mGluR agonists, (1S,3S)-1-aminocyclopentane-1, 3-dicarboxylate ((1S,3s)-ACPD) and (2S, 1'R, 2'R, 3'R)-2-(2',3'-dicarboxycyclopropyl)glycine (DCG-IV) also depressed basal synaptic transmission in a reversible and dose-dependent manner. The mean depression obtained with 200 microM (1S,3S)-ACPD was 83 +/- 8% and the IC50 value was 12 +/- 3 microM (n = 5). The mean depression obtained with 1 microM DCG-IV was 73 +/- 7% and the IC50 value was 88 +/- 15 nM (n = 4). 4. Synaptic depressions induced by the actions of 20 microM (1S,3S)-ACPD and 10 microM L-AP4 were antagonized by the mGluR antagonists (+)-alpha-methyl-4-carboxyphenylglycine ((+)-MCPG), (S)-2-methyl-2-amino-4-phosphonobutanoate (MAP4), (2S,1'S,2'S)-2-methyl-2(2'-carboxycyclopropyl)glycine (MCCG), (RS)-alpha-methyl-4-tetrazolylphenylglycine (MTPG), (RS)-alpha-methyl-4-sulphonophenylglycine (MSPG) and (RS)-alpha-methyl-4-phosphonophenylglycine (MPPG) (all tested at 500 microM). 5. (+)-MCPG was a weak antagonist of both L-AP4 and (1S,3S)-ACPD-induced depressions. MCCG was selective towards (1S,3S)-ACPD, but analysis of its effects were complicated by apparent partial agonist activity. MAP4 showed good selectivity for L-AP4-induced effects. 6

  11. Pharmacological antagonism of the actions of group II and III mGluR agonists in the lateral perforant path of rat hippocampal slices.

    PubMed Central

    Bushell, T. J.; Jane, D. E.; Tse, H. W.; Watkins, J. C.; Garthwaite, J.; Collingridge, G. L.

    1996-01-01

    1. An understanding of the physiological and pathological roles of metabotropic glutamate receptors (mGluRs) is currently hampered by the lack of selective antagonists. Standard extracellular recording techniques were used to investigate the activity of recently reported mGluR antagonists on agonist-induced depressions of synaptic transmission in the lateral perforant path of hippocampal slices obtained from 12-16 day-old rats. 2. The group III specific mGluR agonist, (S)-2-amino-4-phosphonobutanoate (L-AP4) depressed basal synaptic transmission in a reversible and dose-dependent manner. The mean (+/-s.e. mean) depression obtained with 100 microM L-AP4 (the maximum concentration tested) was 74 +/- 3% and the IC50 value was 3 +/- 1 microM (n = 5). 3. The selective group II mGluR agonists, (1S,3S)-1-aminocyclopentane-1, 3-dicarboxylate ((1S,3s)-ACPD) and (2S, 1'R, 2'R, 3'R)-2-(2',3'-dicarboxycyclopropyl)glycine (DCG-IV) also depressed basal synaptic transmission in a reversible and dose-dependent manner. The mean depression obtained with 200 microM (1S,3S)-ACPD was 83 +/- 8% and the IC50 value was 12 +/- 3 microM (n = 5). The mean depression obtained with 1 microM DCG-IV was 73 +/- 7% and the IC50 value was 88 +/- 15 nM (n = 4). 4. Synaptic depressions induced by the actions of 20 microM (1S,3S)-ACPD and 10 microM L-AP4 were antagonized by the mGluR antagonists (+)-alpha-methyl-4-carboxyphenylglycine ((+)-MCPG), (S)-2-methyl-2-amino-4-phosphonobutanoate (MAP4), (2S,1'S,2'S)-2-methyl-2(2'-carboxycyclopropyl)glycine (MCCG), (RS)-alpha-methyl-4-tetrazolylphenylglycine (MTPG), (RS)-alpha-methyl-4-sulphonophenylglycine (MSPG) and (RS)-alpha-methyl-4-phosphonophenylglycine (MPPG) (all tested at 500 microM). 5. (+)-MCPG was a weak antagonist of both L-AP4 and (1S,3S)-ACPD-induced depressions. MCCG was selective towards (1S,3S)-ACPD, but analysis of its effects were complicated by apparent partial agonist activity. MAP4 showed good selectivity for L-AP4-induced effects. 6

  12. Differentiation of sigma ligand-activated receptor subtypes that modulate NMDA-evoked [3H]-noradrenaline release in rat hippocampal slices.

    PubMed Central

    Monnet, F. P.; de Costa, B. R.; Bowen, W. D.

    1996-01-01

    1. It is now widely accepted that there are two classes of sigma (sigma) binding sites, denoted sigma(1) and sigma(2), and recently sigma(3) subtype has been proposed. Selective sigma(1) and sigma(2) receptor agonists are known to modulate the neuronal response to N-methyl-D-aspartate (NMDA) in vivo and in vitro. To identify the site of action of a series of recently synthesised high affinity sigma ligands, the present in vitro series of experiments was carried out on NMDA-evoked [3H]-noradrenaline ([3H]-NA) overflow from preloaded hippocampal slices of the rat. 2. The ligands (+)-cis-N-methyl-N-[2,(3,4-dichlorophenyl) ethyl]-2-(1-pyrrolidinyl) cyclohexylamine (BD-737) and (+)-pentazocine, considered as the prototypic sigma(1) agonists, potentiated the NMDA response from 10 nM to 100 nM. This potentiation faded between 100 nM and 1 microM ligand concentrations. On the other hand, 1,3-di(2-tolyl)guanidine (DTG), a mixed sigma(1)/sigma(2) agonist, at concentrations greater than 100 nM inhibited the NMDA-evoked [3H]-NA release. Spiperone, considered as active on putative sigma(3) receptors, was without effect on the NMDA response, or on the potentiating effect of BD-737. 3. The high affinity sigma antagonists haloperidol and 1[2-(3,4-dichlorophenyl)ethyl]-4-methylpiperazine (BD-1063), inactive by themselves on the NMDA-induced response, at concentrations above 30 nM totally prevented the potentiating effect of (+)-pentazocine (100 nM) as well as the inhibitory effect of DTG (300 nM) on NMDA-evoked [3H]-NA release. Whereas haloperidol and BD-1063, at concentrations < 1 microM, were inactive on the potentiating effect of BD-737 (100 nM). 4. 4-(4-Chlorophenyl)-alpha-4-fluorophenyl-4-hydroxy-1-piperidinebutanol (reduced haloperidol), N-[2-(3,4-dichlorophenyl)ethyl]-N-methyl-2-(1-pyrrolidinyl)ethylamine (BD-1008), inactive by themselves on the NMDA-evoked [3H]-NA release, failed to reverse the effects of (+)-pentazocine and DTG, but at concentrations of 30 nM to 1 micro

  13. Differential Needs of Zinc in the CA3 Area of Dorsal Hippocampus for the Consolidation of Contextual Fear and Spatial Memories

    ERIC Educational Resources Information Center

    Ceccom, Johnatan; Bouhsira, Emilie; Halley, Helene; Daumas, Stephanie; Lassalle, Jean Michel

    2013-01-01

    One peculiarity of the hippocampal CA3 mossy fiber terminals is the co-release of zinc and glutamate upon synaptic transmission. How these two players act on hippocampal-dependent memories is still unclear. To decipher their respective involvement in memory consolidation, a pharmacological approach was chosen. Using two hippocampal-dependent…

  14. Stress-induced remodeling of hippocampal CA3 pyramidal neurons.

    PubMed

    McEwen, Bruce S

    2016-08-15

    The discovery of steroid hormone receptors in brain regions that mediate virtually every aspect of brain function has broadened the definition of 'neuroendocrinology' to include the reciprocal communication between the brain and the body via hormonal and neural pathways. The brain is the central organ of stress and adaptation to stress because it perceives and determines what is threatening, as well as determining the behavioral and physiological responses to the stressor. The adult and developing brain possess remarkable structural and functional plasticity in response to stress, including neurogenesis leading to neuronal replacement, dendritic remodeling, and synapse turnover. Stress causes an imbalance of neural circuitry subserving cognition, decision-making, anxiety and mood that can alter expression of those behaviors and behavioral states. The two Brain Research papers noted in this review played an important role in triggering these advances. This article is part of a Special Issue entitled SI:50th Anniversary Issue. PMID:26740399

  15. The functional nature of synaptic circuitry is altered in area CA3 of the hippocampus in a mouse model of Down's syndrome

    PubMed Central

    Hanson, Jesse E; Blank, Martina; Valenzuela, Ricardo A; Garner, Craig C; Madison, Daniel V

    2007-01-01

    Down's syndrome (DS) is the most common cause of mental retardation, and memory impairments are more severe in DS than in most if not all other causes of mental retardation. The Ts65Dn mouse, a genetic model of DS, exhibits phenotypes of DS, including memory impairments indicative of hippocampal dysfunction. We examined functional synaptic connectivity in area CA3 of the hippocampus of Ts65Dn mice using organotypic slice cultures as a model. We found reductions in multiple measures of synaptic function in both excitatory and inhibitory inputs to pyramidal neurons in CA3 of the Ts65Dn hippocampus. However, associational synaptic connections between pyramidal neurons were more abundant and more likely to be active rather than silent in the Ts65Dn hippocampus. Synaptic potentiation was normal in these associational connections. Decreased overall functional synaptic input onto pyramidal neurons expressed along with the specific hyperconnectivity of associational connections between pyramidal neurons will result in predictable alterations of CA3 network function, which may contribute to the memory impairments seen in DS. PMID:17158177

  16. Nearly Automatic Segmentation of Hippocampal Subfields in In Vivo Focal T2-Weighted MRI

    PubMed Central

    Yushkevich, Paul A.; Wang, Hongzhi; Pluta, John; Das, Sandhitsu R.; Craige, Caryne; Avants, Brian B.; Weiner, Michael W.; Mueller, Susanne

    2010-01-01

    We present and evaluate a new method for automatically labeling the subfields of the hippocampal formation in focal 0.4×0.5×2.0mm3 resolution T2-weighted magnetic resonance images that can be acquired in the routine clinical setting with under 5 min scan time. The method combines multi-atlas segmentation, similarity-weighted voting, and a novel learning-based bias correction technique to achieve excellent agreement with manual segmentation. Initial partitioning of MRI slices into hippocampal ‘head’, ‘body’ and ‘tail’ slices is the only input required from the user, necessitated by the nature of the underlying segmentation protocol. Dice overlap between manual and automatic segmentation is above 0.87 for the larger subfields, CA1 and dentate gyrus, and is competitive with the best results for whole-hippocampus segmentation in the literature. Intraclass correlation of volume measurements in CA1 and dentate gyrus is above 0.89. Overlap in smaller hippocampal subfields is lower in magnitude (0.54 for CA2, 0.62 for CA3, 0.77 for subiculum and 0.79 for entorhinal cortex) but comparable to overlap between manual segmentations by trained human raters. These results support the feasibility of subfield-specific hippocampal morphometry in clinical studies of memory and neurodegenerative disease. PMID:20600984

  17. BID Mediates Oxygen-Glucose Deprivation-Induced Neuronal Injury in Organotypic Hippocampal Slice Cultures and Modulates Tissue Inflammation in a Transient Focal Cerebral Ischemia Model without Changing Lesion Volume

    PubMed Central

    Martin, Nellie Anne; Bonner, Helena; Elkjær, Maria Louise; D’Orsi, Beatrice; Chen, Gang; König, Hans Georg; Svensson, Martina; Deierborg, Tomas; Pfeiffer, Shona; Prehn, Jochen H.; Lambertsen, Kate Lykke

    2016-01-01

    The BH3 interacting-domain death agonist (BID) is a pro-apoptotic protein involved in death receptor-induced and mitochondria-mediated apoptosis. Recently, it has also been suggested that BID is involved in the regulation of inflammatory responses in the central nervous system. We found that BID deficiency protected organotypic hippocampal slice cultures in vitro from neuronal injury induced by oxygen-glucose deprivation. In vivo, BID-knockout (KO) mice and wild type (WT) mice were subjected to 60 min of transient middle cerebral artery occlusion (tMCAO) to induce focal cerebral ischemia, and allowed to recover for 24 h. Infarct volumes and functional outcome were assessed and the inflammatory response was evaluated using immunofluorescence, Western blotting, quantitative PCR (qPCR) and Mesoscale multiplex analysis. We observed no difference in the infarct volume or neurological outcome between BID-KO and WT mice. The inflammatory response was reduced by BID deficiency as indicated by a change in microglial/leukocyte response. In conclusion, our data suggest that BID deficiency is neuroprotective in an in vitro model and modulates the inflammatory response to focal cerebral ischemia in vivo. However, this is not translated into a robust neuroprotection in vivo. PMID:26869884

  18. Oscillatory dynamics in the hippocampus support dentate gyrus–CA3 coupling

    PubMed Central

    Akam, Thomas; Oren, Iris; Mantoan, Laura; Ferenczi, Emily; Kullmann, Dimitri M

    2012-01-01

    Gamma oscillations in the dentate gyrus and hippocampal CA3 show variable coherence in vivo, but the mechanisms and relevance for information flow are unknown. We found that carbachol-induced oscillations in rat CA3 have biphasic phase-response curves, consistent with the ability to couple with oscillations in afferent projections. Differences in response to stimulation of either the intrinsic feedback circuit or the dentate gyrus were well described by varying an impulse vector in a two-dimensional dynamical system, representing the relative input to excitatory and inhibitory neurons. Responses to sinusoidally modulated optogenetic stimulation confirmed that the CA3 network oscillation can entrain to periodic inputs, with a steep dependence of entrainment phase on input frequency. CA3 oscillations are therefore suited to coupling with oscillations in the dentate gyrus over a broad range of frequencies. PMID:22466505

  19. Oscillatory dynamics in the hippocampus support dentate gyrus–CA3 coupling.

    PubMed

    Akam, Thomas; Oren, Iris; Mantoan, Laura; Ferenczi, Emily; Kullmann, Dimitri M

    2012-05-01

    Gamma oscillations in the dentate gyrus and hippocampal CA3 show variable coherence in vivo, but the mechanisms and relevance for information flow are unknown. We found that carbachol-induced oscillations in rat CA3 have biphasic phase-response curves, consistent with the ability to couple with oscillations in afferent projections. Differences in response to stimulation of either the intrinsic feedback circuit or the dentate gyrus were well described by varying an impulse vector in a two-dimensional dynamical system, representing the relative input to excitatory and inhibitory neurons. Responses to sinusoidally modulated optogenetic stimulation confirmed that the CA3 network oscillation can entrain to periodic inputs, with a steep dependence of entrainment phase on input frequency. CA3 oscillations are therefore suited to coupling with oscillations in the dentate gyrus over a broad range of frequencies. PMID:22466505

  20. Symmetric spike timing-dependent plasticity at CA3CA3 synapses optimizes storage and recall in autoassociative networks

    PubMed Central

    Mishra, Rajiv K.; Kim, Sooyun; Guzman, Segundo J.; Jonas, Peter

    2016-01-01

    CA3CA3 recurrent excitatory synapses are thought to play a key role in memory storage and pattern completion. Whether the plasticity properties of these synapses are consistent with their proposed network functions remains unclear. Here, we examine the properties of spike timing-dependent plasticity (STDP) at CA3CA3 synapses. Low-frequency pairing of excitatory postsynaptic potentials (EPSPs) and action potentials (APs) induces long-term potentiation (LTP), independent of temporal order. The STDP curve is symmetric and broad (half-width ∼150 ms). Consistent with these STDP induction properties, AP–EPSP sequences lead to supralinear summation of spine [Ca2+] transients. Furthermore, afterdepolarizations (ADPs) following APs efficiently propagate into dendrites of CA3 pyramidal neurons, and EPSPs summate with dendritic ADPs. In autoassociative network models, storage and recall are more robust with symmetric than with asymmetric STDP rules. Thus, a specialized STDP induction rule allows reliable storage and recall of information in the hippocampal CA3 network. PMID:27174042

  1. Coincidence detection of convergent perforant path and mossy fibre inputs by CA3 interneurons.

    PubMed

    Calixto, Eduardo; Galván, Emilio J; Card, J Patrick; Barrionuevo, Germán

    2008-06-01

    We performed whole-cell recordings from CA3 s. radiatum (R) and s. lacunosum-moleculare (L-M) interneurons in hippocampal slices to examine the temporal aspects of summation of converging perforant path (PP) and mossy fibre (MF) inputs. PP EPSPs were evoked from the s. lacunosum-moleculare in area CA1. MF EPSPs were evoked from the medial extent of the suprapyramidal blade of the dentate gyrus. Summation was strongly supralinear when examining PP EPSP with MF EPSP in a heterosynaptic pair at the 10 ms ISI, and linear to sublinear at longer ISIs. This pattern of nonlinearities suggests that R and L-M interneurons act as coincidence detectors for input from PP and MF. Summation at all ISIs was linear in voltage clamp mode demonstrating that nonlinearities were generated by postsynaptic voltage-dependent conductances. Supralinearity was not detected when the first EPSP in the pair was replaced by a simulated EPSP injected into the soma, suggesting that the conductances underlying the EPSP boosting were located in distal dendrites. Supralinearity was selectively eliminated with either Ni2+ (30 microm), mibefradil (10 microm) or nimodipine (15 microm), but was unaffected by QX-314. This pharmacological profile indicates that supralinearity is due to recruitment of dendritic T-type Ca2+channels by the first subthreshold EPSP in the pair. Results with the hyperpolarization-activated (Ih) channel blocker ZD 7288 (50 microm) revealed that Ih restricted the time course of supralinearity for coincidently summed EPSPs, and promoted linear to sublinear summation for asynchronous EPSPs. We conclude that coincidence detection results from the counterbalanced activation of T-type Ca2+ channels and inactivation of Ih. PMID:18388134

  2. CAPS1 stabilizes the state of readily releasable synaptic vesicles to fusion competence at CA3–CA1 synapses in adult hippocampus

    PubMed Central

    Shinoda, Yo; Ishii, Chiaki; Fukazawa, Yugo; Sadakata, Tetsushi; Ishii, Yuki; Sano, Yoshitake; Iwasato, Takuji; Itohara, Shigeyoshi; Furuichi, Teiichi

    2016-01-01

    Calcium-dependent activator protein for secretion 1 (CAPS1) regulates exocytosis of dense-core vesicles in neuroendocrine cells and of synaptic vesicles in neurons. However, the synaptic function of CAPS1 in the mature brain is unclear because Caps1 knockout (KO) results in neonatal death. Here, using forebrain-specific Caps1 conditional KO (cKO) mice, we demonstrate, for the first time, a critical role of CAPS1 in adult synapses. The amplitude of synaptic transmission at CA3–CA1 synapses was strongly reduced, and paired-pulse facilitation was significantly increased, in acute hippocampal slices from cKO mice compared with control mice, suggesting a perturbation in presynaptic function. Morphological analysis revealed an accumulation of synaptic vesicles in the presynapse without any overall morphological change. Interestingly, however, the percentage of docked vesicles was markedly decreased in the Caps1 cKO. Taken together, our findings suggest that CAPS1 stabilizes the state of readily releasable synaptic vesicles, thereby enhancing neurotransmitter release at hippocampal synapses. PMID:27545744

  3. Topography of Place Maps along the CA3-to-CA2 Axis of the Hippocampus.

    PubMed

    Lu, Li; Igarashi, Kei M; Witter, Menno P; Moser, Edvard I; Moser, May-Britt

    2015-09-01

    We asked whether the structural heterogeneity of the hippocampal CA3-CA2 axis is reflected in how space is mapped onto place cells in CA3-CA2. Place fields were smaller and sharper in proximal CA3 than in distal CA3 and CA2. The proximodistal shift was accompanied by a progressive loss in the ability of place cells to distinguish configurations of the same spatial environment, as well as a reduction in the extent to which place cells formed uncorrelated representations for different environments. The transition to similar representations was nonlinear, with the sharpest drop in distal CA3. These functional changes along the CA3-CA2 axis mirror gradients in gene expression and connectivity that partly override cytoarchitectonic boundaries between the subfields of the hippocampus. The results point to the CA3-CA2 axis as a functionally graded system with powerful pattern separation at the proximal end, near the dentate gyrus, and stronger pattern completion at the CA2 end. PMID:26298277

  4. Gonadal Steroids: Effects on Excitability of Hippocampal Pyramidal Cells

    NASA Astrophysics Data System (ADS)

    Teyler, Timothy J.; Vardaris, Richard M.; Lewis, Deborah; Rawitch, Allen B.

    1980-08-01

    Electrophysiological field potentials from hippocampal slices of rat brain show sex-linked differences in response to 1 × 10-10M concentrations of estradiol and testosterone added to the incubation medium. Slices from male rats show increased excitability to estradiol and not to testosterone. Slices from female rats are not affected by estradiol, but slices from female rats in diestrus show increased excitability in response to testosterone whereas slices from females in proestrus show decreased excitability.

  5. The Role of Gastrodin on Hippocampal Neurons after N-Methyl-D-Aspartate Excitotoxicity and Experimental Temporal Lobe Seizures.

    PubMed

    Wong, Shi-Bing; Hung, Wei-Chen; Min, Ming-Yuan

    2016-06-30

    Tian ma (Gastrodia elata, GE) is an ancient Chinese herbal medicine that has been suggested to be effective as an anticonvulsant and analgesic, and to have sedative effects against vertigo, general paralysis, epilepsy and tetanus. The primary active ingredient isolated from GE is termed gastrodin, which is the glucoside of 4-hydroxybenzyl alcohol (4-HBA). Gastrodin can abolish hypoxia-, glutamate- and N-methyl-D-aspartate (NMDA) receptor-induced toxicity in primary culture of rat cortical neurons, and reduces seizure severity in seizure-sensitive gerbils. We evaluated the effect of gastrodin on NMDA excitotoxicity in hippocampal slice cultures (HSCs) with propidium iodide (PI) fluorescence measurement. We also evaluated the effects of gastrodin for treating active in vivo temporal lobe seizures induced by lithium/pilocarpine. Seizure severity, time span to seizure onset, mortality rate and hippocampal histology for survivors were compared. The effect of gastrodin was evaluated for treating in vitro seizures induced by Mg²⁺-free medium in hippocampal slices. Frequencies and amplitudes of epileptiform discharges were compared. The effect of gastrodin on synaptic transmission was evaluated on hippocampal CA1 Schaffer collaterals. Application of 25 μM gastrodin significantly suppressed NMDA excitotoxicity in CA3 but not in CA1 hippocampus and dentate gyrus. Intraventricular gastrodin accelerated seizure onset for 12 min after intraperitoneal pilocarpine injection (P = 0.051). Three of five rats (60%) in the gastrodin group, and three of four (75%) in the dimethyl sulfoxide (DMSO) group died within 3 days after status epilepticus (SE). Gastrodin also failed to inhibit epileptiform discharges in hippocampal slices induced by Mg²⁺-free medium, believed to be NMDA receptor-mediated spontaneous activity. The frequencies of the spontaneous epileptiform discharges were similar under treatments with 25 μM gastrodin, 200 μM gastrodin and DMSO. For the evaluation of

  6. Dissociated Signals in Human Dentate Gyrus and CA3 Predict Different Facets of Recognition Memory

    PubMed Central

    Reagh, Zachariah M.; Watabe, Joseph; Ly, Maria; Murray, Elizabeth

    2014-01-01

    A wealth of evidence has implicated the hippocampus and surrounding medial temporal lobe cortices in support of recognition memory. However, the roles of the various subfields of the hippocampus are poorly understood. In this study, we concurrently varied stimulus familiarization and repetition to engage different facets of recognition memory. Using high-resolution fMRI (1.5 mm isotropic), we observed distinct familiarity and repetition-related recognition signal profiles in the dentate gyrus (DG)/CA3 subfield in human subjects. The DG/CA3 demonstrated robust response suppression with repetition and familiarity-related facilitation. Both of these discrete responses were predictive of different aspects of behavioral performance. Consistent with previous work, we observed novelty responses in CA1 consistent with “match/mismatch detection,” as well as mixed recognition signaling distributed across medial temporal lobe cortices. Additional analyses indicated that the repetition and familiarity-related signals in the DG/CA3 were strikingly dissociated along the hippocampal longitudinal axis and that activity in the posterior hippocampus was strongly correlated with the retrosplenial cortex. These data provide novel insight into the roles of hippocampal subfields in support of recognition memory and further provide evidence of a functional heterogeneity in the human DG/CA3, particularly along the longitudinal axis. PMID:25274810

  7. Activity-dependent plasticity of mouse hippocampal assemblies in vitro

    PubMed Central

    Keller, Martin K.; Draguhn, Andreas; Both, Martin; Reichinnek, Susanne

    2015-01-01

    Memory formation is associated with the generation of transiently stable neuronal assemblies. In hippocampal networks, such groups of functionally coupled neurons express highly ordered spatiotemporal activity patterns which are coordinated by local network oscillations. One of these patterns, sharp wave-ripple complexes (SPW-R), repetitively activates previously established groups of memory-encoding neurons, thereby supporting memory consolidation. This function implies that repetition of specific SPW-R induces plastic changes which render the underlying neuronal assemblies more stable. We modeled this repetitive activation in an in vitro model of SPW-R in mouse hippocampal slices. Weak electrical stimulation upstream of the CA3-CA1 networks reliably induced SPW-R of stereotypic waveform, thus representing re-activation of similar neuronal activity patterns. Frequent repetition of these patterns (100 times) reduced the variance of both, evoked and spontaneous SPW-R waveforms, indicating stabilization of pre-existing assemblies. These effects were most pronounced in the CA1 subfield and depended on the timing of stimulation relative to spontaneous SPW-R. Additionally, plasticity of SPW-R was blocked by application of a NMDA receptor antagonist, suggesting a role for associative synaptic plasticity in this process. Thus, repetitive activation of specific patterns of SPW-R causes stabilization of memory-related networks. PMID:26041998

  8. Neuronal MHC Class I Molecules are Involved in Excitatory Synaptic Transmission at the Hippocampal Mossy Fiber Synapses of Marmoset Monkeys

    PubMed Central

    Zhang, Mingyue; Schlumbohm, Christina; Mätz-Rensing, Kerstin; Uchanska-Ziegler, Barbara; Flügge, Gabriele; Zhang, Weiqi; Walter, Lutz; Fuchs, Eberhard

    2010-01-01

    Several recent studies suggested a role for neuronal major histocompatibility complex class I (MHCI) molecules in certain forms of synaptic plasticity in the hippocampus of rodents. Here, we report for the first time on the expression pattern and functional properties of MHCI molecules in the hippocampus of a nonhuman primate, the common marmoset monkey (Callithrix jacchus). We detected a presynaptic, mossy fiber-specific localization of MHCI proteins within the marmoset hippocampus. MHCI molecules were present in the large, VGlut1-positive, mossy fiber terminals, which provide input to CA3 pyramidal neurons. Furthermore, whole-cell recordings of CA3 pyramidal neurons in acute hippocampal slices of the common marmoset demonstrated that application of antibodies which specifically block MHCI proteins caused a significant decrease in the frequency, and a transient increase in the amplitude, of spontaneous excitatory postsynaptic currents (sEPSCs) in CA3 pyramidal neurons. These findings add to previous studies on neuronal MHCI molecules by describing their expression and localization in the primate hippocampus and by implicating them in plasticity-related processes at the mossy fiber–CA3 synapses. In addition, our results suggest significant interspecies differences in the localization of neuronal MHCI molecules in the hippocampus of mice and marmosets, as well as in their potential function in these species. Electronic supplementary material The online version of this article (doi:10.1007/s10571-010-9510-3) contains supplementary material, which is available to authorized users. PMID:20232136

  9. Simvastatin enhances hippocampal long-term potentiation in C57BL/6 mice

    PubMed Central

    Mans, Robert A.; Chowdhury, Nazma; Cao, Dongfeng; McMahon, Lori L.; Li, Ling

    2010-01-01

    Statins inhibit 3-hydroxy-3-methylglutaryl CoA reductase (HMG-CoA), the rate-limiting enzyme in the cholesterol biosynthetic pathway, and they are widely used to control plasma cholesterol levels and prevent cardiovascular disease. However, emerging evidence indicates that the beneficial effects of statins extend to the central nervous system. Statins have been shown to improve the outcome of stroke and traumatic brain injury, and statin use has been associated with a reduced prevalence of Alzheimer’s disease (AD) and dementia. However, prospective studies with statins in AD have produced mixed results. Recently, we reported that simvastatin, a widely used statin in humans, enhances learning and memory in non-transgenic mice as well as in transgenic mice with AD-like pathology on a mixed genetic background. However, the cellular and molecular mechanisms underlying the beneficial effects of simvastatin on learning and memory remain elusive. The present study was undertaken to investigate the effect of acute simvastatin treatment on hippocampal long-term potentiation (LTP), a cellular model of learning and memory, in brain slices from C57BL/6 mice. Our results demonstrate that a prolonged in vitro simvastatin treatment for 2-4 hrs, but not a short-term 20-min exposure, significantly increases the magnitude of LTP at CA3-CA1 synapses without altering basal synaptic transmission or the paired-pulse facilitation ratio in hippocampal slices. Furthermore, we show that phosphorylation of Akt (protein kinase B) is increased significantly in the CA1 region following 2-hour treatment with simvastatin, and that inhibition of Akt phosphorylation suppresses the simvastatin-induced enhancement of LTP. These findings suggest activation of Akt as a molecular pathway for augmented hippocampal LTP by simvastatin treatment, and implicate enhancement of hippocampal LTP as a potential cellular mechanism underlying the beneficial effects of simvastatin on cognitive function. PMID

  10. O-GlcNAcylation of AMPA Receptor GluA2 Is Associated with a Novel Form of Long-Term Depression at Hippocampal Synapses

    PubMed Central

    Taylor, Erica W.; Wang, Kai; Nelson, Amy R.; Bredemann, Teruko M.; Fraser, Kyle B.; Clinton, Sarah M.; Puckett, Rosemary; Marchase, Richard B.; Chatham, John C.

    2014-01-01

    Serine phosphorylation of AMPA receptor (AMPAR) subunits GluA1 and GluA2 modulates AMPAR trafficking during long-term changes in strength of hippocampal excitatory transmission required for normal learning and memory. The post-translational addition and removal of O-linked β-N-acetylglucosamine (O-GlcNAc) also occurs on serine residues. This, together with the high expression of the enzymes O-GlcNAc transferase (OGT) and β-N-acetylglucosamindase (O-GlcNAcase), suggests a potential role for O-GlcNAcylation in modifying synaptic efficacy and cognition. Furthermore, because key synaptic proteins are O-GlcNAcylated, this modification may be as important to brain function as phosphorylation, yet its physiological significance remains unknown. We report that acutely increasing O-GlcNAcylation in Sprague Dawley rat hippocampal slices induces an NMDA receptor and protein kinase C-independent long-term depression (LTD) at hippocampal CA3–CA1 synapses (O-GcNAc LTD). This LTD requires AMPAR GluA2 subunits, which we demonstrate are O-GlcNAcylated. Increasing O-GlcNAcylation interferes with long-term potentiation, and in hippocampal behavioral assays, it prevents novel object recognition and placement without affecting contextual fear conditioning. Our findings provide evidence that O-GlcNAcylation dynamically modulates hippocampal synaptic function and learning and memory, and suggest that altered O-GlcNAc levels could underlie cognitive dysfunction in neurological diseases. PMID:24381264

  11. [A simple vibratome for brain slice].

    PubMed

    Xia, J H; Xing, B R; Gu, Q; Hua, S Y

    1989-12-01

    A simple vibratome was fabricated using double-function electric shaver and microscopic platform. Spontaneous discharge of neurons in hippocampal and hypothalamic brain slices (in 300-400 microns thick) prepared by the vibratome could kept above 12 hours in artificial cerebro-spinal fluid. PMID:2697084

  12. The TNFα-Transgenic Rat: Hippocampal Synaptic Integrity, Cognition, Function, and Post-Ischemic Cell Loss

    PubMed Central

    Pettigrew, L. Creed; Kryscio, Richard J.; Norris, Christopher M.

    2016-01-01

    The cytokine, tumor necrosis factor α (TNFα), is a key regulator of neuroinflammation linked to numerous neurodegenerative conditions and diseases. The present study used transgenic rats that overexpress a murine TNFα gene, under the control of its own promoter, to investigate the impact of chronically elevated TNFα on hippocampal synaptic function. Neuronal viability and cognitive recovery in TNFα Tg rats were also determined following an ischemic insult arising from reversible middle cerebral artery occlusion (MCAO). Basal CA3-CA1 synaptic strength, recorded in acute brain slices, was not significantly different between eight-week-old TNFα Tg rats and non-Tg rats. In contrast, slices from TNFα Tg rats showed significantly greater levels of long-term potentiation (LTP) in response to 100 Hz stimulation, suggesting that synaptic networks may be hyperexcitable in the context of elevated TNFα. Cognitive and motor deficits (assessed on the Morris Water Maze and Rotarod task, respectively) were present in TNFα Tg rats in the absence of significant differences in the loss of cortical and hippocampal neurons. TNF overexpression exacerbated MCAO-dependent deficits on the rotarod, but ameliorated cortical neuron loss in response to MCAO. PMID:27144978

  13. Compartmental distribution of GABAB receptor-mediated currents along the somatodendritic axis of hippocampal principal cells

    PubMed Central

    Degro, Claudius E.; Kulik, Akos; Booker, Sam A.; Vida, Imre

    2015-01-01

    Activity of cortical principal cells is controlled by the GABAergic system providing inhibition in a compartmentalized manner along their somatodendritic axis. While GABAAR-mediated inhibitory synaptic transmission has been extensively characterized in hippocampal principal cells, little is known about the distribution of postsynaptic effects of GABABRs. In the present study, we have investigated the functional localization of GABABRs and their effector inwardly rectifying potassium (Kir3) channels by combining electrophysiological recordings in acute rat hippocampal slices, high-resolution immunoelectron microscopic analysis and single cell simulations. Pharmacologically isolated slow inhibitory postsynaptic currents were elicited in the three major hippocampal principal cell types by endogenous GABA released by electrical stimulation, photolysis of caged-GABA, as well as the canonical agonist baclofen, with the highest amplitudes observed in the CA3. Spatially restricted currents were assessed along the axis of principal cells by uncaging GABA in the different hippocampal layers. GABABR-mediated currents were present along the entire somatodendritic axis of principal cells, but non-uniformly distributed: largest currents and the highest conductance densities determined in the simulations were consistently found on the distal apical dendrites. Finally, immunocytochemical localization of GABABRs and Kir3 channels showed that distributions overlap but their densities diverge, particularly on the basal dendrites of pyramidal cells. GABABRs current amplitudes and the conductance densities correlated better with Kir3 density, suggesting a bottlenecking effect defined by the effector channel. These data demonstrate a compartmentalized distribution of the GABABR-Kir3 signaling cascade and suggest differential control of synaptic transmission, dendritic integration and synaptic plasticity at afferent pathways onto hippocampal principal cells. PMID:25852540

  14. Hippocampal MR volumetry

    NASA Astrophysics Data System (ADS)

    Haller, John W.; Botteron, K.; Brunsden, Barry S.; Sheline, Yvette I.; Walkup, Ronald K.; Black, Kevin J.; Gado, Mokhtar; Vannier, Michael W.

    1994-09-01

    Goal: To estimate hippocampal volumes from in vivo 3D magnetic resonance (MR) brain images and determine inter-rater and intra- rater repeatability. Objective: The precision and repeatability of hippocampal volume estimates using stereologic measurement methods is sought. Design: Five normal control and five schizophrenic subjects were MR scanned using a MPRAGE protocol. Fixed grid stereologic methods were used to estimate hippocampal volumes on a graphics workstation. The images were preprocessed using histogram analysis to standardize 3D MR image scaling from 16 to 8 bits and image volumes were interpolated to 0.5 mm3 isotropic voxels. The following variables were constant for the repeated stereologic measures: grid size, inter-slice distance (1.5 mm), voxel dimensions (0.5 mm3), number of hippocampi measured (10), total number of measurements per rater (40), and number of raters (5). Two grid sizes were tested to determine the coefficient of error associated with the number of sampled 'hits' (approximately 140 and 280) on the hippocampus. Starting slice and grid position were randomly varied to assure unbiased volume estimates. Raters were blind to subject identity, diagnosis, and side of the brain from which the image volumes were extracted and the order of subject presentation was randomized for each of the raters. Inter- and intra-rater intraclass correlation coefficients (ICC) were determined. Results: The data indicate excellent repeatability of fixed grid stereologic hippocampal volume measures when using an inter-slice distance of 1.5 mm and a 6.25 mm2 grid (inter-rater ICCs equals 0.86 - 0.97, intra- rater ICCs equals 0.85 - 0.97). One major advantage of the current study was the use of 3D MR data which significantly improved visualization of hippocampal boundaries by providing the ability to access simultaneous orthogonal views while counting stereological marks within the hippocampus. Conclusion: Stereological estimates of 3D volumes from 2D MR

  15. Model-Based Assessment of an In-Vivo Predictive Relationship from CA1 to CA3 in the Rodent Hippocampus

    PubMed Central

    Sandler, Roman A.; Song, Dong; Hampson, Robert E.; Deadwyler, Sam A.; Berger, Theodore W.; Marmarelis, Vasilis Z.

    2014-01-01

    Although an anatomical connection from CA1 to CA3 via the Entorhinal Cortex (EC) and through backprojecting interneurons has long been known it exist, it has never been examined quantitatively on the single neuron level, in the in-vivo nonpatholgical, nonperturbed brain. Here, single spike activity was recorded using a multi-electrode array from the CA3 and CA1 areas of the rodent hippocampus (N=7) during a behavioral task. The predictive power from CA3→CA1 and CA1→CA3 was examined by constructing Multivariate Autoregressive (MVAR) models from recorded neurons in both directions. All nonsignificant inputs and models were identified and removed by means of Monte Carlo simulation methods. It was found that 121/166 (73%) CA3→CA1 models and 96/145 (66%) CA1→CA3 models had significant predictive power, thus confirming a predictive ‘Granger’ causal relationship from CA1 to CA3. This relationship is thought to be caused by a combination of truly causal connections such as the CA1→EC→CA3 pathway and common inputs such as those from the Septum. All MVAR models were then examined in the frequency domain and it was found that CA3 kernels had significantly more power in the theta and beta range than those of CA1, confirming CA3’s role as an endogenous hippocampal pacemaker. PMID:25260381

  16. Dentate gyrus–CA3 glutamate release/NMDA transmission mediates behavioral despair and antidepressant-like responses to leptin

    PubMed Central

    Wang, Xuezhen; Zhang, Di; Lu, Xin-Yun

    2014-01-01

    Compelling evidence supports the important role of the glutamatergic system in the pathophysiology of major depression and also as a target for rapid-acting antidepressants. However, the functional role of glutamate release/transmission in behavioral processes related to depression and antidepressant efficacy remains to be elucidated. In this study, glutamate release and behavioral responses to tail suspension, a procedure commonly used for inducing behavioral despair, were simultaneously monitored in real time. The onset of tail suspension stress evoked a rapid increase in glutamate release in hippocampal field CA3, which declined gradually after its offset. Blockade of NMDA receptors by intra-CA3 infusion of MK-801, a non-competitive NMDA receptor antagonist, reversed behavioral despair. The CA3 was innervated by granule neurons expressing the leptin receptor (LepRb) in the dentate gyrus (DG), representing a subpopulation of granule neurons that were devoid of stress-induced activation. Leptin treatment dampened tail suspension-evoked glutamate release in CA3. On the other hand, intra-CA3 infusion of NMDA blocked the antidepressant-like effect of leptin in reversing behavioral despair in both the tail suspension and forced swim tests, which involved activation of Akt signaling in DG. Together, these results suggest that the DG-CA3 glutamatergic pathway is critical for mediating behavioral despair and antidepressant-like responses to leptin. PMID:25092243

  17. Mnemonic Functions for Nonlinear Dendritic Integration in Hippocampal Pyramidal Circuits.

    PubMed

    Kaifosh, Patrick; Losonczy, Attila

    2016-05-01

    We present a model for neural circuit mechanisms underlying hippocampal memory. Central to this model are nonlinear interactions between anatomically and functionally segregated inputs onto dendrites of pyramidal cells in hippocampal areas CA3 and CA1. We study the consequences of such interactions using model neurons in which somatic burst-firing and synaptic plasticity are controlled by conjunctive processing of these separately integrated input pathways. We find that nonlinear dendritic input processing enhances the model's capacity to store and retrieve large numbers of similar memories. During memory encoding, CA3 stores heavily decorrelated engrams to prevent interference between similar memories, while CA1 pairs these engrams with information-rich memory representations that will later provide meaningful output signals during memory recall. While maintaining mathematical tractability, this model brings theoretical study of memory operations closer to the hippocampal circuit's anatomical and physiological properties, thus providing a framework for future experimental and theoretical study of hippocampal function. PMID:27146266

  18. High-Speed imaging reveals opposing effects of chronic stress and antidepressants on neuronal activity propagation through the hippocampal trisynaptic circuit.

    PubMed

    Stepan, Jens; Hladky, Florian; Uribe, Andrés; Holsboer, Florian; Schmidt, Mathias V; Eder, Matthias

    2015-01-01

    Antidepressants (ADs) are used as first-line treatment for most stress-related psychiatric disorders. The alterations in brain circuit dynamics that can arise from stress exposure and underlie therapeutic actions of ADs remain, however, poorly understood. Here, enabled by a recently developed voltage-sensitive dye imaging (VSDI) assay in mouse brain slices, we examined the impact of chronic stress and concentration-dependent effects of eight clinically used ADs (belonging to different chemical/functional classes) on evoked neuronal activity propagations through the hippocampal trisynaptic circuitry (HTC: perforant path → dentate gyrus (DG) → area CA3 → area CA1). Exposure of mice to chronic social defeat stress led to markedly weakened activity propagations ("HTC-Waves"). In contrast, at concentrations in the low micromolar range, all ADs, which were bath applied to slices, caused an amplification of HTC-Waves in CA regions (invariably in area CA1). The fast-acting "antidepressant" ketamine, the mood stabilizer lithium, and brain-derived neurotrophic factor (BDNF) exerted comparable enhancing effects, whereas the antipsychotic haloperidol and the anxiolytic diazepam attenuated HTC-Waves. Collectively, we provide direct experimental evidence that chronic stress can depress neuronal signal flow through the HTC and demonstrate shared opposing effects of ADs. Thus, our study points to a circuit-level mechanism of ADs to counteract stress-induced impairment of hippocampal network function. However, the observed effects of ADs are impossible to depend on enhanced neurogenesis. PMID:26594153

  19. High-Speed imaging reveals opposing effects of chronic stress and antidepressants on neuronal activity propagation through the hippocampal trisynaptic circuit

    PubMed Central

    Stepan, Jens; Hladky, Florian; Uribe, Andrés; Holsboer, Florian; Schmidt, Mathias V.; Eder, Matthias

    2015-01-01

    Antidepressants (ADs) are used as first-line treatment for most stress-related psychiatric disorders. The alterations in brain circuit dynamics that can arise from stress exposure and underlie therapeutic actions of ADs remain, however, poorly understood. Here, enabled by a recently developed voltage-sensitive dye imaging (VSDI) assay in mouse brain slices, we examined the impact of chronic stress and concentration-dependent effects of eight clinically used ADs (belonging to different chemical/functional classes) on evoked neuronal activity propagations through the hippocampal trisynaptic circuitry (HTC: perforant path → dentate gyrus (DG) → area CA3 → area CA1). Exposure of mice to chronic social defeat stress led to markedly weakened activity propagations (“HTC-Waves”). In contrast, at concentrations in the low micromolar range, all ADs, which were bath applied to slices, caused an amplification of HTC-Waves in CA regions (invariably in area CA1). The fast-acting “antidepressant” ketamine, the mood stabilizer lithium, and brain-derived neurotrophic factor (BDNF) exerted comparable enhancing effects, whereas the antipsychotic haloperidol and the anxiolytic diazepam attenuated HTC-Waves. Collectively, we provide direct experimental evidence that chronic stress can depress neuronal signal flow through the HTC and demonstrate shared opposing effects of ADs. Thus, our study points to a circuit-level mechanism of ADs to counteract stress-induced impairment of hippocampal network function. However, the observed effects of ADs are impossible to depend on enhanced neurogenesis. PMID:26594153

  20. Persistent Receptor Activity Underlies Group I mGluR-Mediated Cellular Plasticity in CA3 Neuron

    PubMed Central

    Young, Steven R.; Chuang, Shih-Chieh; Zhao, Wangfa; Wong, Robert K.S.; Bianchi, Riccardo

    2013-01-01

    Plastic changes in cortical activities induced by group I metabotropic glutamate receptor (mGluR) stimulation include epileptogenesis, expressed in vitro as the conversion of normal neuronal activity to persistent, prolonged synchronized (ictal) discharges. At present, the mechanism that maintains group I mGluR-induced plasticity is not known. We examined this issue using hippocampal slices from guinea pigs and mice. Agonist [(S)-3,5-dihydroxyphenylglycine; DHPG; 30– 50 μM)] stimulation of group I mGluRs induces persistent prolonged synchronized (ictal-like) discharges in CA3 that are associated with three identified excitatory cellular responses – suppression of spike afterhyperpolarizations, activation of a voltage-dependent cationic current, and increase in neuronal input resistance. Persistent prolonged synchronized discharges and the underlying excitatory cellular responses maintained following induction were reversibly blocked by mGluR1 antagonists [LY 367385; (S)-+-α-amino-4-carboxy-2-methylbenzeneacetic acid; 50, 100 μM; CPCCOEt (hydroxyimino)cyclopropa[b]chromen-1a-carboxylate ethyl ester; 100 μM], and to a lesser extent by the mGluR5 antagonist MPEP [2-methyl-6-(phenylethynyl)pyridine hydrochloride; 50 μM]. Activation of persistent cellular responses to DHPG were unaffected by tetrodotoxin (0.5–1 μM) or perfusion with low Ca2+(0.2 mM)-Mn2+(0.5 mM) media – conditions that suppress endogenous glutamate release. The pharmacological profile of the blocking action of the group I mGluR antagonist MCPG [(RS)-α-methyl-4-carboxyphenylglycine; 50–500 μM] on persistent cellular responses was different from that on cellular responses directly activated by DHPG. These data indicate that transient stimulation of group I mGluRs alters receptor properties rendering them persistently active in the absence of applied agonist or endogenous glutamate activation. Persistent receptor activities, primarily involving mGluR1, maintain excitatory cellular

  1. Thick Slice and Thin Slice Teaching Evaluations

    ERIC Educational Resources Information Center

    Tom, Gail; Tong, Stephanie Tom; Hesse, Charles

    2010-01-01

    Student-based teaching evaluations are an integral component to institutions of higher education. Previous work on student-based teaching evaluations suggest that evaluations of instructors based upon "thin slice" 30-s video clips of them in the classroom correlate strongly with their end of the term "thick slice" student evaluations. This study's…

  2. Immature hippocampal neuronal networks do not develop tolerance to the excitatory actions of ethanol.

    PubMed

    Galindo, Rafael; Valenzuela, C Fernando

    2006-10-01

    Ethanol (EtOH) damages the hippocampus, a brain region that is involved in learning and memory processes. The mechanisms responsible for this effect of EtOH are not fully understood. We recently demonstrated that acute EtOH exposure potently stimulates oscillatory activity driven by the excitatory actions of GABA in the CA3 region of the neonatal rat hippocampus. This activity can be recorded during the growth spurt period as giant depolarizing potentials (GDPs). Here, we characterized the effects of prolonged EtOH exposure on GDPs. In the first study, we prepared hippocampal coronal slices from neonatal rats and exposed these to control artificial cerebrospinal fluid (ACSF) or ACSF plus 50 mM EtOH for 3-4 h. We then performed whole-cell patch-clamp electrophysiological recordings from CA3 pyramidal neurons, which revealed that tolerance to the GDP stimulating effects of EtOH did not occur after continuous exposure. In the second study, we exposed neonatal rats to air or air plus 1.9 g/dl EtOH in vapor chambers for 4h/day for 1 or 3 days (neonatal peak blood EtOH concentration = 40-45 mM). We then performed slice electrophysiological studies 24 h after the end of EtOH exposure and found that there was no statistically significant difference in the acute effect of 50 mM EtOH on GDP frequency in samples from neonates exposed to air or air plus EtOH. These findings indicate that EtOH persistently stimulates network-driven oscillatory activity in the developing hippocampus. We propose that the lack of adaptive response to continuous EtOH exposure could make immature neuronal networks particularly vulnerable to the actions of this agent. PMID:17307647

  3. Effect of chronic stress on synaptic currents in rat hippocampal dentate gyrus neurons.

    PubMed

    Karst, Henk; Joëls, Marian

    2003-01-01

    We investigated the effect of chronic stress on synaptic responses of rat dentate granule cells to perforant path stimulation. Rats were subjected for 3 wk to unpredictable stressors twice daily or to control handling. One day after the last stressor, hippocampal slices were prepared and synaptic responses were determined with whole-cell recording. At that time, adrenal weight was found to be increased and thymus weight as well as gain in body weight were decreased in the stressed versus control animals, indicative of corticosterone hypersecretion during the stress period. In slices from rats with basal corticosteroid levels (at the circadian trough, under rest), no effect of prior stress exposure was observed on synaptic responses. However, synaptic responses of dentate granule cells from chronically stressed and control rats were differently affected by in vitro activation of glucocorticoid receptors, i.e., 1-4 h after administration of 100 nM corticosterone for 20 min. Thus the maximal response to synaptic activation of dentate cells at holding potential of -70 mV [when N-methyl-D-aspartate (NMDA) receptors are blocked by magnesium] was significantly enhanced after corticosterone administration in chronically stressed but not in control animals. In accordance, the amplitude of alpha-amino-3-hydroxy-5-methylisolazole-4-propionic acid (AMPA) but not of NMDA receptor-mediated currents was increased by corticosterone in stressed rats, over the entire voltage range. Corticosterone treatment also decreased the time to peak of AMPA currents, but this effect did not depend on prior stress exposure. The data indicate that following chronic stress exposure synaptic excitation of dentate granule cells may be enhanced when corticosterone levels rise. This enhanced synaptic flow could contribute to enhanced excitation of projection areas of the dentate gyrus, most notably the CA3 hippocampal region. PMID:12522207

  4. Diabetic hyperglycemia aggravates seizures and status epilepticus-induced hippocampal damage.

    PubMed

    Huang, Chin-Wei; Cheng, Juei-Tang; Tsai, Jing-Jane; Wu, Sheng-Nan; Huang, Chao-Ching

    2009-01-01

    Epileptic seizures in diabetic hyperglycemia (DH) are not uncommon. This study aimed to determine the acute behavioral, pathological, and electrophysiological effects of status epilepticus (SE) on diabetic animals. Adult male Sprague-Dawley rats were first divided into groups with and without streptozotocin (STZ)-induced diabetes, and then into treatment groups given a normal saline (NS) (STZ-only and NS-only) or a lithium-pilocarpine injection to induce status epilepticus (STZ + SE and NS + SE). Seizure susceptibility, severity, and mortality were evaluated. Serial Morris water maze test and hippocampal histopathology results were examined before and 24 h after SE. Tetanic stimulation-induced long-term potentiation (LTP) in a hippocampal slice was recorded in a multi-electrode dish system. We also used a simulation model to evaluate intracellular adenosine triphosphate (ATP) and neuroexcitability. The STZ + SE group had a significantly higher percentage of severe seizures and SE-related death and worse learning and memory performances than the other three groups 24 h after SE. The STZ + SE group, and then the NS + SE group, showed the most severe neuronal loss and mossy fiber sprouting in the hippocampal CA3 area. In addition, LTP was markedly attenuated in the STZ + SE group, and then the NS + SE group. In the simulation, increased intracellular ATP concentration promoted action potential firing. This finding that rats with DH had more brain damage after SE than rats without diabetes suggests the importance of intensively treating hyperglycemia and seizures in diabetic patients with epilepsy. PMID:19384590

  5. Adolescent mice show anxiety- and aggressive-like behavior and the reduction of long-term potentiation in mossy fiber-CA3 synapses after neonatal maternal separation.

    PubMed

    Shin, S Y; Han, S H; Woo, R-S; Jang, S H; Min, S S

    2016-03-01

    Exposure to maternal separation (MS) during early life is an identified risk factor for emotional disorders such as anxiety and depression later in life. This study investigated the effects of neonatal MS on the behavior and long-term potentiation (LTP) as well as basic synaptic transmission at hippocampal CA3-CA1 and mossy fiber (MF)-CA3 synapses in adolescent mice for 19days. When mice were adolescents, we measured depression, learning, memory, anxious and aggressive behavior using the forced swimming test (FST), Y-maze, Morris water maze (MWM), elevated plus maze (EPM), three consecutive days of the open field test, the social interaction test, the tube-dominance test and the resident-intruder test. The results showed that there was no difference in FST, Y-maze, and MWM performance. However, MS mice showed more anxiety-like behavior in the EPM test and aggressive-like behavior in the tube-dominance and resident-intruder tests. In addition, the magnitude of LTP and release probability in the MF-CA3 synapses was reduced in the MS group but not in the CA3-CA1 synapse. Our results indicate that early life stress due to MS may induce anxiety- and aggressive-like behavior during adolescence, and these effects are associated with synaptic plasticity at the hippocampal MF-CA3 synapses. PMID:26733385

  6. Left–right dissociation of hippocampal memory processes in mice

    PubMed Central

    Shipton, Olivia A.; El-Gaby, Mohamady; Apergis-Schoute, John; Deisseroth, Karl; Bannerman, David M.; Paulsen, Ole; Kohl, Michael M.

    2014-01-01

    Left–right asymmetries have likely evolved to make optimal use of bilaterian nervous systems; however, little is known about the synaptic and circuit mechanisms that support divergence of function between equivalent structures in each hemisphere. Here we examined whether lateralized hippocampal memory processing is present in mice, where hemispheric asymmetry at the CA3–CA1 pyramidal neuron synapse has recently been demonstrated, with different spine morphology, glutamate receptor content, and synaptic plasticity, depending on whether afferents originate in the left or right CA3. To address this question, we used optogenetics to acutely silence CA3 pyramidal neurons in either the left or right dorsal hippocampus while mice performed hippocampus-dependent memory tasks. We found that unilateral silencing of either the left or right CA3 was sufficient to impair short-term memory. However, a striking asymmetry emerged in long-term memory, wherein only left CA3 silencing impaired performance on an associative spatial long-term memory task, whereas right CA3 silencing had no effect. To explore whether synaptic properties intrinsic to the hippocampus might contribute to this left–right behavioral asymmetry, we investigated the expression of hippocampal long-term potentiation. Following the induction of long-term potentiation by high-frequency electrical stimulation, synapses between CA3 and CA1 pyramidal neurons were strengthened only when presynaptic input originated in the left CA3, confirming an asymmetry in synaptic properties. The dissociation of hippocampal long-term memory function between hemispheres suggests that memory is routed via distinct left–right pathways within the mouse hippocampus, and provides a promising approach to help elucidate the synaptic basis of long-term memory. PMID:25246561

  7. Comparative NMR studies on Ca3LiRuO6 and Ca3NaRuO6

    NASA Astrophysics Data System (ADS)

    Chakrabarty, T.; Paulose, P. L.

    2016-06-01

    We report a comparative study of two ruthanate compounds, Ca3LiRuO6 and Ca3NaRuO6 by magnetic measurements, heat capacity and NMR. Ca3LiRuO6 is a weak ferromagnet with a magnetic ordering temperature of 115 K. The 7Li NMR linewidth of Ca3LiRuO6 displays a broad shoulder above the magnetic ordering temperature. Anomalous shoulder of this type is observed in the susceptibility data also. The origin of these phenomena is not clear but could possibly be attributed to low dimensional magnetism. A contrasting magnetic behavior is seen in Ca3NaRuO6, an antiferromagnet with a transition temperature at 87 K. The NMR study shows that the Knight shift is proportional to the magnetic susceptibility. Also, in Ca3NaRuO6, the Knight shift and the linewidth of the spectra change differently compared to Ca3LiRuO6. The heat capacity of both compounds show a λ-type anomaly at respective magnetic transition temperatures. However, in both the systems the entropy change (Δ S) is much less than that of an ordered S  =  3/2 system.

  8. Comparative NMR studies on Ca3LiRuO6 and Ca3NaRuO6.

    PubMed

    Chakrabarty, T; Paulose, P L

    2016-06-15

    We report a comparative study of two ruthanate compounds, Ca3LiRuO6 and Ca3NaRuO6 by magnetic measurements, heat capacity and NMR. Ca3LiRuO6 is a weak ferromagnet with a magnetic ordering temperature of 115 K. The (7)Li NMR linewidth of Ca3LiRuO6 displays a broad shoulder above the magnetic ordering temperature. Anomalous shoulder of this type is observed in the susceptibility data also. The origin of these phenomena is not clear but could possibly be attributed to low dimensional magnetism. A contrasting magnetic behavior is seen in Ca3NaRuO6, an antiferromagnet with a transition temperature at 87 K. The NMR study shows that the Knight shift is proportional to the magnetic susceptibility. Also, in Ca3NaRuO6, the Knight shift and the linewidth of the spectra change differently compared to Ca3LiRuO6. The heat capacity of both compounds show a λ-type anomaly at respective magnetic transition temperatures. However, in both the systems the entropy change ([Formula: see text]S) is much less than that of an ordered S  =  3/2 system. PMID:27157888

  9. Thermoelectric properties of antiperovskite calcium oxides Ca3PbO and Ca3SnO

    NASA Astrophysics Data System (ADS)

    Okamoto, Y.; Sakamaki, A.; Takenaka, K.

    2016-05-01

    We report the thermoelectric properties of polycrystalline samples of Ca3Pb1-xBixO (x = 0, 0.1, 0.2) and Ca3SnO, both crystallizing in a cubic antiperovskite-type structure. The Ca3SnO sample shows metallic resistivity and its thermoelectric power approaches 100 μV K-1 at room temperature, resulting in the thermoelectric power factor of Ca3SnO being larger than that of Ca3Pb1-xBixO. On the basis of Hall and Sommerfeld coefficients, the Ca3SnO sample is found to be a p-type metal with a carrier density of ˜1019 cm-3, a mobility of ˜80 cm2 V-1 s-1, both comparable to those in degenerated semiconductors, and a moderately large hole carrier effective mass. The coexistence of moderately high mobility and large effective mass observed in Ca3SnO, as well as possible emergence of a multivalley electronic structure with a small band gap at low-symmetry points in k-space, suggests that the antiperovskite Ca oxides have strong potential as a thermoelectric material.

  10. Melamine Alters Glutamatergic Synaptic Transmission of CA3-CA1 Synapses Presynaptically Through Autophagy Activation in the Rat Hippocampus.

    PubMed

    Zhang, Hui; Wang, Hui; Xiao, Xi; Zhang, Tao

    2016-01-01

    Melamine is an industrial chemical that can cause central nervous system disorders including excitotoxicity and cognitive impairment. Its illegal use in powdered baby formula was the focus of a milk scandal in China in 2008. One of our previous studies showed that melamine impaired glutamatergic transmission in rat hippocampal CA1 pyramidal cells. However, the underlying mechanism of action of melamine is unclear, and it is unknown if the CA3-CA1 pathway is directly involved. In the present study, a whole-cell patch-clamp technique was employed to investigate the effect of melamine on the hippocampal CA3-CA1 pathway in vitro. Both the evoked excitatory postsynaptic current (eEPSC) and the paired-pulse ratio (PPR) were recorded. Furthermore, we examined whether autophagy was involved in glutamatergic transmission alterations induced by melamine. Our data showed that melamine significantly increased the amplitude of eEPSCs in a dose-dependent manner. Inhibition of the N-methyl-D-aspartic acid receptor did not prevent the increase in eEPSC amplitude. In addition, the PPR was remarkably decreased by a melamine concentration of 5 × 10(-5) g/mL. It was found that autophagy could be activated by melamine and an autophagy inhibitor, 3-MA, prevented the melamine-induced increase in eEPSC amplitude. Overall, our results show that melamine presynaptically alters glutamatergic synaptic transmission of hippocampal CA3-CA1 synapses in vitro and this is likely associated with autophagy alteration. PMID:26530910

  11. Ih Tunes Theta/Gamma Oscillations and Cross-Frequency Coupling In an In Silico CA3 Model

    PubMed Central

    Neymotin, Samuel A.; Hilscher, Markus M.; Moulin, Thiago C.; Skolnick, Yosef; Lazarewicz, Maciej T.; Lytton, William W.

    2013-01-01

    channels are uniquely positioned to act as neuromodulatory control points for tuning hippocampal theta (4–12 Hz) and gamma (25 Hz) oscillations, oscillations which are thought to have importance for organization of information flow. contributes to neuronal membrane resonance and resting membrane potential, and is modulated by second messengers. We investigated oscillatory control using a multiscale computer model of hippocampal CA3, where each cell class (pyramidal, basket, and oriens-lacunosum moleculare cells), contained type-appropriate isoforms of . Our model demonstrated that modulation of pyramidal and basket allows tuning theta and gamma oscillation frequency and amplitude. Pyramidal also controlled cross-frequency coupling (CFC) and allowed shifting gamma generation towards particular phases of the theta cycle, effected via 's ability to set pyramidal excitability. Our model predicts that in vivo neuromodulatory control of allows flexibly controlling CFC and the timing of gamma discharges at particular theta phases. PMID:24204609

  12. Quantitative Morphometry of Electrophysiologically Identified CA3b Interneurons Reveals Robust Local Geometry and Distinct Cell Classes

    PubMed Central

    Ascoli, Giorgio A.; Brown, Kerry M.; Calixto, Eduardo; Card, J. Patrick; Galvan, E. J.; Perez-Rosello, T.; Barrionuevo, Germán

    2010-01-01

    The morphological and electrophysiological diversity of inhibitory cells in hippocampal area CA3 may underlie specific computational roles and is not yet fully elucidated. In particular, interneurons with somata in strata radiatum (R) and lacunosum-moleculare (L-M) receive converging stimulation from the dentate gyrus and entorhinal cortex as well as within CA3. Although these cells express different forms of synaptic plasticity, their axonal trees and connectivity are still largely unknown. We investigated the branching and spatial patterns, plus the membrane and synaptic properties, of rat CA3b R and L-M interneurons digitally reconstructed after intracellular labeling. We found considerable variability within but no difference between the two layers, and no correlation between morphological and biophysical properties. Nevertheless, two cell types were identified based on the number of dendritic bifurcations, with significantly different anatomical and electrophysiological features. Axons generally branched an order of magnitude more than dendrites. However, interneurons on both sides of the R/L-M boundary revealed surprisingly modular axo-dendritic arborizations with consistently uniform local branch geometry. Both axons and dendrites followed a lamellar organization, and axons displayed a spatial preference towards the fissure. Moreover, only a small fraction of the axonal arbor extended to the outer portion of the invaded volume, and tended to return towards the proximal region. In contrast, dendritic trees demonstrated more limited but isotropic volume occupancy. These results suggest a role of predominantly local feedforward and lateral inhibitory control for both R and L-M interneurons. Such role may be essential to balance the extensive recurrent excitation of area CA3 underlying hippocampal autoassociative memory function. PMID:19496174

  13. Main determinants of presynaptic Ca2+ dynamics at individual mossy fiber - CA3 pyramidal cell synapses

    PubMed Central

    Scott, Ricardo; Rusakov, Dmitri A.

    2009-01-01

    Synaptic transmission between hippocampal mossy fibers (MFs) and CA3 pyramidal cells exhibits remarkable use-dependent plasticity. The underlying presynaptic mechanisms, however, remain poorly understood. Here we have used fluorescent Ca2+ indicators Fluo-4, Fluo-5F and Oregon Green BAPTA-1 to investigate Ca2+ dynamics in individual giant MF boutons (MFBs) in area CA3 traced from the somata of granule cells held in whole-cell mode. In an individual MFB, a single action potential induces a brief peak of free Ca2+ (estimated in the range of 8-9 μM) followed by an elevation to ~320 nM which slowly decays to its resting level of ~110 nM. Changes in the somatic membrane potential influence presynaptic Ca2+ entry at proximal MFBs in the hilus. This influence decays with distance along the axon, with a length constant of approximately 200 μm. In giant MFBs in CA3, progressive saturation of endogenous Ca2+ buffers during repetitive spiking amplifies rapid Ca2+ peaks and the residual Ca2+ several-fold, suggesting a causal link to synaptic facilitation. We find that internal Ca2+ stores contribute to maintaining the low resting Ca2+ providing ~22% of the buffering/extrusion capacity of giant MFBs. Rapid Ca2+ release from stores represents up to 20% of the presynaptic Ca2+ transient evoked by a brief train of action potentials. The results identify the main components of presynaptic Ca2+ dynamics at this important cortical synapse. PMID:16807336

  14. Parametric Trace Slicing

    NASA Technical Reports Server (NTRS)

    Rosu, Grigore (Inventor); Chen, Feng (Inventor); Chen, Guo-fang; Wu, Yamei; Meredith, Patrick O. (Inventor)

    2014-01-01

    A program trace is obtained and events of the program trace are traversed. For each event identified in traversing the program trace, a trace slice of which the identified event is a part is identified based on the parameter instance of the identified event. For each trace slice of which the identified event is a part, the identified event is added to an end of a record of the trace slice. These parametric trace slices can be used in a variety of different manners, such as for monitoring, mining, and predicting.

  15. Preparation of Gene Gun Bullets and Biolistic Transfection of Neurons in Slice Culture

    PubMed Central

    Woods, Georgia; Zito, Karen

    2008-01-01

    Biolistic transfection is a physical means of transfecting cells by bombarding tissue with high velocity DNA coated particles. We provide a detailed protocol for biolistic transfection of rat hippocampal slices, from the initial preparation of DNA coated bullets to the final shooting of the organotypic slice cultures using a gene gun. Gene gun transfection is an efficient and easy means of transfecting neurons and is especially useful for fluorescently labeling a small subset of cells in tissue slice. In this video, we first outline the steps required to coat gold particles with DNA. We next demonstrate how to line the inside of plastic tubing with the gold/DNA bullets, and how to cut this tubing to obtain the plastic cartridges for loading into the gene gun. Finally, we perform biolistic transfection of rat hippocampal slice cultures, demonstrating handling of the Bio-Rad Helios gene gun, and offering trouble shooting advice to obtain healthy and optimally transfected tissue slices. PMID:19066564

  16. Diurnal inhibition of NMDA-EPSCs at rat hippocampal mossy fibre synapses through orexin-2 receptors

    PubMed Central

    Perin, Martina; Longordo, Fabio; Massonnet, Christine; Welker, Egbert; Lüthi, Anita

    2014-01-01

    Diurnal release of the orexin neuropeptides orexin-A (Ox-A, hypocretin-1) and orexin-B (Ox-B, hypocretin-2) stabilises arousal, regulates energy homeostasis and contributes to cognition and learning. However, whether cellular correlates of brain plasticity are regulated through orexins, and whether they do so in a time-of-day-dependent manner, has never been assessed. Immunohistochemically we found sparse but widespread innervation of hippocampal subfields through Ox-A- and Ox-B-containing fibres in young adult rats. The actions of Ox-A were studied on NMDA receptor (NMDAR)-mediated excitatory synaptic transmission in acute hippocampal slices prepared around the trough (Zeitgeber time (ZT) 4–8, corresponding to 4–8 h into the resting phase) and peak (ZT 23) of intracerebroventricular orexin levels. At ZT 4–8, exogenous Ox-A (100 nm in bath) inhibited NMDA receptor-mediated excitatory postsynaptic currents (NMDA-EPSCs) at mossy fibre (MF)–CA3 (to 55.6 ± 6.8% of control, P = 0.0003) and at Schaffer collateral–CA1 synapses (70.8 ± 6.3%, P = 0.013), whereas it remained ineffective at non-MF excitatory synapses in CA3. Ox-A actions were mediated postsynaptically and blocked by the orexin-2 receptor (OX2R) antagonist JNJ10397049 (1 μm), but not by orexin-1 receptor inhibition (SB334867, 1 μm) or by adrenergic and cholinergic antagonists. At ZT 23, inhibitory effects of exogenous Ox-A were absent (97.6 ± 2.9%, P = 0.42), but reinstated (87.2 ± 3.3%, P = 0.002) when endogenous orexin signalling was attenuated for 5 h through i.p. injections of almorexant (100 mg kg−1), a dual orexin receptor antagonist. In conclusion, endogenous orexins modulate hippocampal NMDAR function in a time-of-day-dependent manner, suggesting that they may influence cellular plasticity and consequent variations in memory performance across the sleep–wake cycle. PMID:25085886

  17. Associative Retrieval Processes in the Human Medial Temporal Lobe: Hippocampal Retrieval Success and CA1 Mismatch Detection

    ERIC Educational Resources Information Center

    Chen, Janice; Olsen, Rosanna K.; Preston, Alison R.; Glover, Gary H.; Wagner, Anthony D.

    2011-01-01

    Hippocampal subfields CA3 and CA1 are hypothesized to differentially support the generation of associative predictions and the detection of associative mismatches, respectively. Using high-resolution functional MRI, we examined hippocampal subfield activation during associative retrieval and during subsequent comparisons of memory to matching or…

  18. Aging-Related Hyperexcitability in CA3 Pyramidal Neurons Is Mediated by Enhanced A-Type K+ Channel Function and Expression.

    PubMed

    Simkin, Dina; Hattori, Shoai; Ybarra, Natividad; Musial, Timothy F; Buss, Eric W; Richter, Hannah; Oh, M Matthew; Nicholson, Daniel A; Disterhoft, John F

    2015-09-23

    Aging-related impairments in hippocampus-dependent cognition have been attributed to maladaptive changes in the functional properties of pyramidal neurons within the hippocampal subregions. Much evidence has come from work on CA1 pyramidal neurons, with CA3 pyramidal neurons receiving comparatively less attention despite its age-related hyperactivation being postulated to interfere with spatial processing in the hippocampal circuit. Here, we use whole-cell current-clamp to demonstrate that aged rat (29-32 months) CA3 pyramidal neurons fire significantly more action potentials (APs) during theta-burst frequency stimulation and that this is associated with faster AP repolarization (i.e., narrower AP half-widths and enlarged fast afterhyperpolarization). Using a combination of patch-clamp physiology, pharmacology, Western blot analyses, immunohistochemistry, and array tomography, we demonstrate that these faster AP kinetics are mediated by enhanced function and expression of Kv4.2/Kv4.3 A-type K(+) channels, particularly within the perisomatic compartment, of CA3 pyramidal neurons. Thus, our study indicates that inhibition of these A-type K(+) channels can restore the intrinsic excitability properties of aged CA3 pyramidal neurons to a young-like state. Significance statement: Age-related learning deficits have been attributed, in part, to altered hippocampal pyramidal neuronal function with normal aging. Much evidence has come from work on CA1 neurons, with CA3 neurons receiving comparatively less attention despite its age-related hyperactivation being postulated to interfere with spatial processing. Hence, we conducted a series of experiments to identify the cellular mechanisms that underlie the hyperexcitability reported in the CA3 region. Contrary to CA1 neurons, we demonstrate that postburst afterhyperpolarization is not altered with aging and that aged CA3 pyramidal neurons are able to fire significantly more action potentials and that this is associated with

  19. Aging-Related Hyperexcitability in CA3 Pyramidal Neurons Is Mediated by Enhanced A-Type K+ Channel Function and Expression

    PubMed Central

    Simkin, Dina; Hattori, Shoai; Ybarra, Natividad; Musial, Timothy F.; Buss, Eric W.; Richter, Hannah; Oh, M. Matthew

    2015-01-01

    Aging-related impairments in hippocampus-dependent cognition have been attributed to maladaptive changes in the functional properties of pyramidal neurons within the hippocampal subregions. Much evidence has come from work on CA1 pyramidal neurons, with CA3 pyramidal neurons receiving comparatively less attention despite its age-related hyperactivation being postulated to interfere with spatial processing in the hippocampal circuit. Here, we use whole-cell current-clamp to demonstrate that aged rat (29–32 months) CA3 pyramidal neurons fire significantly more action potentials (APs) during theta-burst frequency stimulation and that this is associated with faster AP repolarization (i.e., narrower AP half-widths and enlarged fast afterhyperpolarization). Using a combination of patch-clamp physiology, pharmacology, Western blot analyses, immunohistochemistry, and array tomography, we demonstrate that these faster AP kinetics are mediated by enhanced function and expression of Kv4.2/Kv4.3 A-type K+ channels, particularly within the perisomatic compartment, of CA3 pyramidal neurons. Thus, our study indicates that inhibition of these A-type K+ channels can restore the intrinsic excitability properties of aged CA3 pyramidal neurons to a young-like state. SIGNIFICANCE STATEMENT Age-related learning deficits have been attributed, in part, to altered hippocampal pyramidal neuronal function with normal aging. Much evidence has come from work on CA1 neurons, with CA3 neurons receiving comparatively less attention despite its age-related hyperactivation being postulated to interfere with spatial processing. Hence, we conducted a series of experiments to identify the cellular mechanisms that underlie the hyperexcitability reported in the CA3 region. Contrary to CA1 neurons, we demonstrate that postburst afterhyperpolarization is not altered with aging and that aged CA3 pyramidal neurons are able to fire significantly more action potentials and that this is associated with

  20. Pannexin-1-mediated ATP release from area CA3 drives mGlu5-dependent neuronal oscillations.

    PubMed

    Lopatář, Jan; Dale, Nicholas; Frenguelli, Bruno G

    2015-06-01

    The activation of Group I metabotropic glutamate receptors (GI mGluRs) in the hippocampus results in the appearance of persistent bursts of synchronised neuronal activity. In response to other stimuli, such activity is known to cause the release of the purines ATP and its neuroactive metabolite, adenosine. We have thus investigated the potential release and role of the purines during GI mGluR-induced oscillations in rat hippocampal areas CA3 and CA1 using pharmacological techniques and microelectrode biosensors for ATP and adenosine. The GI mGluR agonist DHPG induced both persistent oscillations in neuronal activity and the release of adenosine in areas CA1 and CA3. In contrast, the DHPG-induced release of ATP was only observed in area CA3. Whilst adenosine acting at adenosine A1 receptors suppressed DHPG-induced burst activity, the activation of mGlu5 and P2Y1 ATP receptors were necessary for the induction of DHPG-induced oscillations. Selective inhibition of pannexin-1 hemichannels with a low concentration of carbenoxolone (10 μM) or probenecid (1 mM) did not affect adenosine release in area CA3, but prevented both ATP release in area CA3 and DHPG-induced bursting. These data reveal key aspects of GI mGluR-dependent neuronal activity that are subject to bidirectional regulation by ATP and adenosine in the initiation and pacing of burst firing, respectively, and which have implications for the role of GI mGluRs in seizure activity and neurodevelopmental disorders. PMID:25645390

  1. Automated Factor Slice Sampling.

    PubMed

    Tibbits, Matthew M; Groendyke, Chris; Haran, Murali; Liechty, John C

    2014-01-01

    Markov chain Monte Carlo (MCMC) algorithms offer a very general approach for sampling from arbitrary distributions. However, designing and tuning MCMC algorithms for each new distribution, can be challenging and time consuming. It is particularly difficult to create an efficient sampler when there is strong dependence among the variables in a multivariate distribution. We describe a two-pronged approach for constructing efficient, automated MCMC algorithms: (1) we propose the "factor slice sampler", a generalization of the univariate slice sampler where we treat the selection of a coordinate basis (factors) as an additional tuning parameter, and (2) we develop an approach for automatically selecting tuning parameters in order to construct an efficient factor slice sampler. In addition to automating the factor slice sampler, our tuning approach also applies to the standard univariate slice samplers. We demonstrate the efficiency and general applicability of our automated MCMC algorithm with a number of illustrative examples. PMID:24955002

  2. Automated Factor Slice Sampling

    PubMed Central

    Tibbits, Matthew M.; Groendyke, Chris; Haran, Murali; Liechty, John C.

    2013-01-01

    Markov chain Monte Carlo (MCMC) algorithms offer a very general approach for sampling from arbitrary distributions. However, designing and tuning MCMC algorithms for each new distribution, can be challenging and time consuming. It is particularly difficult to create an efficient sampler when there is strong dependence among the variables in a multivariate distribution. We describe a two-pronged approach for constructing efficient, automated MCMC algorithms: (1) we propose the “factor slice sampler”, a generalization of the univariate slice sampler where we treat the selection of a coordinate basis (factors) as an additional tuning parameter, and (2) we develop an approach for automatically selecting tuning parameters in order to construct an efficient factor slice sampler. In addition to automating the factor slice sampler, our tuning approach also applies to the standard univariate slice samplers. We demonstrate the efficiency and general applicability of our automated MCMC algorithm with a number of illustrative examples. PMID:24955002

  3. Active Sulforhodamine 101 Uptake into Hippocampal Astrocytes

    PubMed Central

    Schnell, Christian; Hagos, Yohannes; Hülsmann, Swen

    2012-01-01

    Sulforhodamine 101 (SR101) is widely used as a marker of astrocytes. In this study we investigated labeling of astrocytes by SR101 in acute slices from the ventrolateral medulla and the hippocampus of transgenic mice expressing EGFP under the control of the astrocyte-specific human GFAP promoter. While SR101 efficiently and specifically labeled EGFP-expressing astrocytes in hippocampus, we found that the same staining procedure failed to label astrocytes efficiently in the ventrolateral medulla. Although carbenoxolone is able to decrease the SR101-labeling of astrocytes in the hippocampus, it is unlikely that SR101 is taken up via gap-junction hemichannels because mefloquine, a blocker for pannexin and connexin hemichannels, was unable to prevent SR101-labeling of hippocampal astrocytes. However, SR101-labeling of the hippocampal astrocytes was significantly reduced by substrates of organic anion transport polypeptides, including estron-3-sulfate and dehydroepiandrosterone sulfate, suggesting that SR101 is actively transported into hippocampal astrocytes. PMID:23189143

  4. Identification of Potentially Neuroprotective Genes Upregulated by Neurotrophin Treatment of CA3 Neurons in the Injured Brain

    PubMed Central

    Malik, Saafan Z.; Motamedi, Shahab; Royo, Nicolas C.; LeBold, David

    2011-01-01

    Abstract Specific neurotrophic factors mediate histological and/or functional improvement in animal models of traumatic brain injury (TBI). In previous work, several lines of evidence indicated that the mammalian neurotrophin NT-4/5 is neuroprotective for hippocampal CA3 pyramidal neurons after experimental TBI. We hypothesized that NT-4/5 neuroprotection is mediated by changes in the expression of specific sets of genes, and that NT-4/5-regulated genes are potential therapeutic targets for blocking delayed neuronal death after TBI. In this study, we performed transcription profiling analysis of CA3 neurons to identify genes regulated by lateral fluid percussion injury, or by treatment with the trkB ligands NT-4/5 or brain-derived neurotrophic factor (BDNF). The results indicate extensive overlap between genes upregulated by neurotrophins and genes upregulated by injury, suggesting that the mechanism behind neurotrophin neuroprotection may mimic the brain's endogenous protective response. A subset of genes selected for further study in vitro exhibited neuroprotection against glutamate excitotoxicity. The neuroprotective genes identified in this study were upregulated at 30 h post-injury, and are thus expected to act during a clinically useful time frame of hours to days after injury. Modulation of these factors and pathways by genetic manipulation or small molecules may confer hippocampal neuroprotection in vivo in preclinical models of TBI. PMID:21083427

  5. Behavioral Functions of the CA3 Subregion of the Hippocampus

    ERIC Educational Resources Information Center

    Kesner, Raymond P.

    2007-01-01

    From a behavioral perspective, the CA3a,b subregion of the hippocampus plays an important role in the encoding of new spatial information within short-term memory with a duration of seconds and minutes. This can easily be observed in tasks that require rapid encoding, novelty detection, one-trial short-term or working memory, and one-trial cued…

  6. Prenatal Hypoxia-Ischemia Induces Abnormalities in CA3 Microstructure, Potassium Chloride Co-Transporter 2 Expression and Inhibitory Tone.

    PubMed

    Jantzie, Lauren L; Getsy, Paulina M; Denson, Jesse L; Firl, Daniel J; Maxwell, Jessie R; Rogers, Danny A; Wilson, Christopher G; Robinson, Shenandoah

    2015-01-01

    Infants who suffer perinatal brain injury, including those with encephalopathy of prematurity, are prone to chronic neurological deficits, including epilepsy, cognitive impairment, and behavioral problems, such as anxiety, inattention, and poor social interaction. These deficits, especially in combination, pose the greatest hindrance to these children becoming independent adults. Cerebral function depends on adequate development of essential inhibitory neural circuits and the appropriate amount of excitation and inhibition at specific stages of maturation. Early neuronal synaptic responses to γ-amino butyric acid (GABA) are initially excitatory. During the early postnatal period, GABAAR responses switch to inhibitory with the upregulation of potassium-chloride co-transporter KCC2. With extrusion of chloride by KCC2, the Cl(-) reversal potential shifts and GABA and glycine responses become inhibitory. We hypothesized that prenatal hypoxic-ischemic brain injury chronically impairs the developmental upregulation of KCC2 that is essential for cerebral circuit formation. Following late gestation hypoxia-ischemia (HI), diffusion tensor imaging in juvenile rats shows poor microstructural integrity in the hippocampal CA3 subfield, with reduced fractional anisotropy and elevated radial diffusivity. The loss of microstructure correlates with early reduced KCC2 expression on NeuN-positive pyramidal neurons, and decreased monomeric and oligomeric KCC2 protein expression in the CA3 subfield. Together with decreased inhibitory post-synaptic currents during a critical window of development, we document for the first time that prenatal transient systemic HI in rats impairs hippocampal CA3 inhibitory tone. Failure of timely development of inhibitory tone likely contributes to a lower seizure threshold and impaired cognitive function in children who suffer perinatal brain injury. PMID:26388734

  7. Prenatal Hypoxia–Ischemia Induces Abnormalities in CA3 Microstructure, Potassium Chloride Co-Transporter 2 Expression and Inhibitory Tone

    PubMed Central

    Jantzie, Lauren L.; Getsy, Paulina M.; Denson, Jesse L.; Firl, Daniel J.; Maxwell, Jessie R.; Rogers, Danny A.; Wilson, Christopher G.; Robinson, Shenandoah

    2015-01-01

    Infants who suffer perinatal brain injury, including those with encephalopathy of prematurity, are prone to chronic neurological deficits, including epilepsy, cognitive impairment, and behavioral problems, such as anxiety, inattention, and poor social interaction. These deficits, especially in combination, pose the greatest hindrance to these children becoming independent adults. Cerebral function depends on adequate development of essential inhibitory neural circuits and the appropriate amount of excitation and inhibition at specific stages of maturation. Early neuronal synaptic responses to γ-amino butyric acid (GABA) are initially excitatory. During the early postnatal period, GABAAR responses switch to inhibitory with the upregulation of potassium-chloride co-transporter KCC2. With extrusion of chloride by KCC2, the Cl− reversal potential shifts and GABA and glycine responses become inhibitory. We hypothesized that prenatal hypoxic–ischemic brain injury chronically impairs the developmental upregulation of KCC2 that is essential for cerebral circuit formation. Following late gestation hypoxia–ischemia (HI), diffusion tensor imaging in juvenile rats shows poor microstructural integrity in the hippocampal CA3 subfield, with reduced fractional anisotropy and elevated radial diffusivity. The loss of microstructure correlates with early reduced KCC2 expression on NeuN-positive pyramidal neurons, and decreased monomeric and oligomeric KCC2 protein expression in the CA3 subfield. Together with decreased inhibitory post-synaptic currents during a critical window of development, we document for the first time that prenatal transient systemic HI in rats impairs hippocampal CA3 inhibitory tone. Failure of timely development of inhibitory tone likely contributes to a lower seizure threshold and impaired cognitive function in children who suffer perinatal brain injury. PMID:26388734

  8. Place Cell Rate Remapping by CA3 Recurrent Collaterals

    PubMed Central

    Solstad, Trygve; Yousif, Hosam N.; Sejnowski, Terrence J.

    2014-01-01

    Episodic-like memory is thought to be supported by attractor dynamics in the hippocampus. A possible neural substrate for this memory mechanism is rate remapping, in which the spatial map of place cells encodes contextual information through firing rate variability. To test whether memories are stored as multimodal attractors in populations of place cells, recent experiments morphed one familiar context into another while observing the responses of CA3 cell ensembles. Average population activity in CA3 was reported to transition gradually rather than abruptly from one familiar context to the next, suggesting a lack of attractive forces associated with the two stored representations. On the other hand, individual CA3 cells showed a mix of gradual and abrupt transitions at different points along the morph sequence, and some displayed hysteresis which is a signature of attractor dynamics. To understand whether these seemingly conflicting results are commensurate with attractor network theory, we developed a neural network model of the CA3 with attractors for both position and discrete contexts. We found that for memories stored in overlapping neural ensembles within a single spatial map, position-dependent context attractors made transitions at different points along the morph sequence. Smooth transition curves arose from averaging across the population, while a heterogeneous set of responses was observed on the single unit level. In contrast, orthogonal memories led to abrupt and coherent transitions on both population and single unit levels as experimentally observed when remapping between two independent spatial maps. Strong recurrent feedback entailed a hysteretic effect on the network which diminished with the amount of overlap in the stored memories. These results suggest that context-dependent memory can be supported by overlapping local attractors within a spatial map of CA3 place cells. Similar mechanisms for context-dependent memory may also be found in

  9. Hippocampal subfield and medial temporal cortical persistent activity during working memory reflects ongoing encoding

    PubMed Central

    Nauer, Rachel K.; Whiteman, Andrew S.; Dunne, Matthew F.; Stern, Chantal E.; Schon, Karin

    2015-01-01

    Previous neuroimaging studies support a role for the medial temporal lobes in maintaining novel stimuli over brief working memory (WM) delays, and suggest delay period activity predicts subsequent memory. Additionally, slice recording studies have demonstrated neuronal persistent spiking in entorhinal cortex, perirhinal cortex (PrC), and hippocampus (CA1, CA3, subiculum). These data have led to computational models that suggest persistent spiking in parahippocampal regions could sustain neuronal representations of sensory information over many seconds. This mechanism may support both WM maintenance and encoding of information into long term episodic memory. The goal of the current study was to use high-resolution fMRI to elucidate the contributions of the MTL cortices and hippocampal subfields to WM maintenance as it relates to later episodic recognition memory. We scanned participants while they performed a delayed match to sample task with novel scene stimuli, and assessed their memory for these scenes post-scan. We hypothesized stimulus-driven activation that persists into the delay period—a putative correlate of persistent spiking—would predict later recognition memory. Our results suggest sample and delay period activation in the parahippocampal cortex (PHC), PrC, and subiculum (extending into DG/CA3 and CA1) was linearly related to increases in subsequent memory strength. These data extend previous neuroimaging studies that have constrained their analysis to either the sample or delay period by modeling these together as one continuous ongoing encoding process, and support computational frameworks that predict persistent activity underlies both WM and episodic encoding. PMID:25859188

  10. Slicing black hole spacetimes

    NASA Astrophysics Data System (ADS)

    Bini, Donato; Bittencourt, Eduardo; Geralico, Andrea; Jantzen, Robert T.

    2015-04-01

    A general framework is developed to investigate the properties of useful choices of stationary spacelike slicings of stationary spacetimes whose congruences of timelike orthogonal trajectories are interpreted as the world lines of an associated family of observers, the kinematical properties of which in turn may be used to geometrically characterize the original slicings. On the other hand, properties of the slicings themselves can directly characterize their utility motivated instead by other considerations like the initial value and evolution problems in the 3-plus-1 approach to general relativity. An attempt is made to categorize the various slicing conditions or "time gauges" used in the literature for the most familiar stationary spacetimes: black holes and their flat spacetime limit.