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Eberhard H. Buhl - One of the best experts on this subject based on the ideXlab platform.

  • Unitary IPSPs evoked by interneurons at the Stratum radiatum-Stratum Lacunosum-Moleculare border in the CA1 area of the rat hippocampus in vitro.
    The Journal of physiology, 1998
    Co-Authors: Imre Vida, K. Halasy, Csaba Szinyei, P Somogyi, Eberhard H. Buhl
    Abstract:

    1. Hippocampal non-principal neurons at the Stratum radiatum-Stratum Lacunosum-Moleculare border (R-LM interneurons) of the CA1 area may constitute several cell classes and have been implicated in the generation of GABAergic unitary IPSPs. Using biocytin-filled electrodes we recorded R-LM interneurons intracellularly in vitro and determined their postsynaptic effects in concomitantly recorded pyramidal cells. 2. Light microscopic analysis revealed four populations of R-LM interneurons with distinct axons: (1) basket cells (n = 4) with axons predominantly ramifying in the pyramidal cell layer; (2) Schaffer collateral/commissural pathway-associated interneurons (n = 10) stratifying in Stratum radiatum and, to a lesser extent, Stratum oriens; (3) perforant pathway-associated interneurons (n = 6) innervating the perforant path termination zone in Stratum Lacunosum-Moleculare of the CA1 area as well as equivalent portions of the dentate gyrus and subiculum; and (4) neurogliaform interneurons (n = 2) characterized by their dense, compact axonal and dendritic arbour. 3. Random electron microscopic sampling of synaptic targets revealed a preponderance of pyramidal neurons as postsynaptic elements. Basket cells had a synaptic target preference for somata and proximal dendrites, whereas the remainder of R-LM interneurons innervated dendritic shafts and spines. The axon of dendrite-targeting cells formed up to six putative contacts with individual postsynatpic pyramidal cells. 4. Anatomically recovered R-LM interneurons (n = 22) had a mean resting membrane potential of -56.7 +/- 3.6 mV, a membrane time constant of 12.9 +/- 7.7 ms and an input resistance of 86.4 +/- 29.2 M omega. Depolarizing current pulses generally elicited overshooting action potentials (70.8 +/- 6.9 mV) which had a mean duration, when measured at half-amplitude, of 0.7 +/- 0.1 ms. In response to prolonged (> 200 ms) depolarizing current pulses all R-LM interneurons displayed (a varying degree of) spike frequency adaptation. 5. Basket cells, Schaffer-associated and neurogliaform interneurons elicited small-amplitude (< 2 mV), short-latency IPSPs in postsynaptic pyramids (n = 5, 13 and 1, respectively). Those interactions in which an effect was elicited with the repetitive activation of the presynaptic neuron (n = 13) showed a substantial degree of postsynaptic response summation. Unitary IPSPs had fast kinetics and, whenever tested (n = 5; 1 basket cell and 4 Schaffer-associated interneurons), were abolished by the GABAA receptor antagonist bicuculline. 6. Thus, R-LM interneurons comprise several distinct populations which evoke fast GABAA receptor mediated IPSPs. The domain-specific innervation of postsynaptic pyramidal cells suggests functionally diverse effects on the integration of afferent information in functionally non-equivalent compartments of pyramidal cells.

  • Unitary IPSPs evoked by interneurons at the Stratum radiatum‐Stratum Lacunosum‐Moleculare border in the CA1 area of the rat hippocampus in vitro
    The Journal of Physiology, 1998
    Co-Authors: Imre Vida, Peter Somogyi, K. Halasy, Csaba Szinyei, Eberhard H. Buhl
    Abstract:

    1. Hippocampal non-principal neurons at the Stratum radiatum-Stratum Lacunosum-Moleculare border (R-LM interneurons) of the CA1 area may constitute several cell classes and have been implicated in the generation of GABAergic unitary IPSPs. Using biocytin-filled electrodes we recorded R-LM interneurons intracellularly in vitro and determined their postsynaptic effects in concomitantly recorded pyramidal cells. 2. Light microscopic analysis revealed four populations of R-LM interneurons with distinct axons: (1) basket cells (n = 4) with axons predominantly ramifying in the pyramidal cell layer; (2) Schaffer collateral/commissural pathway-associated interneurons (n = 10) stratifying in Stratum radiatum and, to a lesser extent, Stratum oriens; (3) perforant pathway-associated interneurons (n = 6) innervating the perforant path termination zone in Stratum Lacunosum-Moleculare of the CA1 area as well as equivalent portions of the dentate gyrus and subiculum; and (4) neurogliaform interneurons (n = 2) characterized by their dense, compact axonal and dendritic arbour. 3. Random electron microscopic sampling of synaptic targets revealed a preponderance of pyramidal neurons as postsynaptic elements. Basket cells had a synaptic target preference for somata and proximal dendrites, whereas the remainder of R-LM interneurons innervated dendritic shafts and spines. The axon of dendrite-targeting cells formed up to six putative contacts with individual postsynatpic pyramidal cells. 4. Anatomically recovered R-LM interneurons (n = 22) had a mean resting membrane potential of -56.7 +/- 3.6 mV, a membrane time constant of 12.9 +/- 7.7 ms and an input resistance of 86.4 +/- 29.2 M omega. Depolarizing current pulses generally elicited overshooting action potentials (70.8 +/- 6.9 mV) which had a mean duration, when measured at half-amplitude, of 0.7 +/- 0.1 ms. In response to prolonged (> 200 ms) depolarizing current pulses all R-LM interneurons displayed (a varying degree of) spike frequency adaptation. 5. Basket cells, Schaffer-associated and neurogliaform interneurons elicited small-amplitude (< 2 mV), short-latency IPSPs in postsynaptic pyramids (n = 5, 13 and 1, respectively). Those interactions in which an effect was elicited with the repetitive activation of the presynaptic neuron (n = 13) showed a substantial degree of postsynaptic response summation. Unitary IPSPs had fast kinetics and, whenever tested (n = 5; 1 basket cell and 4 Schaffer-associated interneurons), were abolished by the GABAA receptor antagonist bicuculline. 6. Thus, R-LM interneurons comprise several distinct populations which evoke fast GABAA receptor mediated IPSPs. The domain-specific innervation of postsynaptic pyramidal cells suggests functionally diverse effects on the integration of afferent information in functionally non-equivalent compartments of pyramidal cells.

Gianmaria Maccaferri - One of the best experts on this subject based on the ideXlab platform.

  • Optogenetic activation of cajal-retzius cells reveals their glutamatergic output and a novel feedforward circuit in the developing mouse hippocampus.
    The Journal of neuroscience : the official journal of the Society for Neuroscience, 2014
    Co-Authors: Giulia Quattrocolo, Gianmaria Maccaferri
    Abstract:

    Cajal-Retzius cells orchestrate the development of cortical circuits by secreting the glycoprotein reelin. However, their computational functions are still unknown. In fact, the nature of their postsynaptic targets, major neurotransmitter released, as well as the class of postsynaptic receptors activated by their firing remain unclear. Here, we have addressed these questions by activating Cajal-Retzius cells optogenetically in mouse hippocampal slices. Light delivered to Stratum Lacunosum-Moleculare triggered EPSCs both on local interneurons and on pyramidal cells. Responses recorded under voltage-clamp conditions had identical short latencies and similar amplitudes, but were kinetically different (i.e., faster in interneurons vs pyramidal cells). In both cases, responses were blocked by TTX, indicating that they were generated by action potential-dependent release. Responses in interneurons were rescued by the addition of 4-AP to TTX, and decreased when presynaptic firing in Cajal-Retzius cells was reduced by the chemokine CXCL12, indicating the existence of a direct Cajal-Retzius cell-interneuron monosynaptic connection. Although the combined application of 4-AP and TTX did not rescue responses in pyramidal cells, neither were they affected by the GABAA receptor blocker gabazine, which would be expected if they were polysynaptic. Both connections showed physiological and pharmacological properties indicating the involvement of AMPA- and NMDA-type glutamate receptors. The connectivity from presynaptic Cajal-Retzius cells to interneurons was strong enough to generate long-latency feedforward GABAergic input onto pyramidal cells. We propose that this newly defined Cajal-Retzius cell-dependent microcircuit may regulate synaptic plasticity and dendritic development in Stratum Lacunosum-Moleculare, thus impacting the integrative properties of the developing hippocampus.

  • The chemokine CXCL12 and the HIV‐1 envelope protein gp120 regulate spontaneous activity of Cajal–Retzius cells in opposite directions
    The Journal of physiology, 2012
    Co-Authors: Ivan Marchionni, Michael Beaumont, Gianmaria Maccaferri
    Abstract:

    Activation of the CXC chemokine receptor 4 (CXCR4) in Cajal–Retzius cells by CXC chemokine ligand 12 (CXCL12) is important for controlling their excitability. CXCR4 is also a co-receptor for the glycoprotein 120 (gp120) of the envelope of the human immunodeficiency virus type 1 (HIV-1), and binding of gp120 to CXCR4 may produce pathological effects. In order to study CXCR4-dependent modulation of membrane excitability, we recorded in cell-attached configuration spontaneous action currents from hippocampal Stratum Lacunosum-Moleculare Cajal–Retzius cells of the CXCR4-EGFP mouse. CXCL12 (50 nM) powerfully inhibited firing independently of synaptic transmission, suggesting that CXCR4 regulates an intrinsic conductance. This effect was prevented by conditioning slices with BAPTA-AM (200 μM), and by blockers of the BK calcium-dependent potassium channels (TEA (1 mM), paxilline (10 μM) and iberiotoxin (100 nM)). In contrast, exposure to gp120 (pico- to nanomolar range, alone or in combination with soluble cluster of differentiation 4 (CD4)), enhanced spontaneous firing frequency. This effect was prevented by the CXCR4 antagonist AMD3100 (1 μM) and was absent in EGFP-negative Stratum Lacunosum-Moleculare interneurons. Increased excitability was prevented by treating slices with BAPTA-AM or bumetanide, suggesting that gp120 activates a mechanism that is both calcium- and chloride-dependent. In conclusion, our results demonstrate that CXCL12 and gp120 modulate the excitability of Cajal–Retzius cells in opposite directions. We propose that CXCL12 and gp120 either generate calcium responses of different strength or activate distinct pools of intracellular calcium, leading to agonist-specific responses, mediated by BK channels in the case of CXCL12, and by a chloride-dependent mechanism in the case of gp120.

  • Modulation of hippocampal Stratum Lacunosum-Moleculare microcircuits.
    The Journal of Physiology, 2011
    Co-Authors: Gianmaria Maccaferri
    Abstract:

    Abstract  Although the rigorous anatomical definition of the microcircuitry of the brain is essential for understanding its functions, the modulation of the physiological properties of neurons and synapses may confer an additional level of complexity. Here, I review two examples of neuromodulation within a specific microcircuit of the hippocampus, i.e. the local network of Stratum Lacunosum-Moleculare. In particular, I will examine the actions of two different types of neuromodulators on the excitability and electrical coupling of two specific classes of cells. First, I will review the effects of noradrenaline on GABAergic networks. Particular emphasis will be placed on neurogliaform cells. Then, I will describe the chemokinergic modulation of spontaneous firing of Cajal–Retzius cells, mediated by the chemokine (C-X-C motif) ligand 12/stromal cell-derived factor-1 α (CXCL12/SDF-1) via the CXC chemokine receptor 4 (CXCR4). The complexities created by these diverse types of modulations for network activity, together with their potential implications for Stratum Lacunosum-Moleculare processing of information in vivo, will be also presented and briefly discussed.

  • Distinctive properties of CXC chemokine receptor 4‐expressing Cajal–Retzius cells versus GABAergic interneurons of the postnatal hippocampus
    The Journal of Physiology, 2010
    Co-Authors: Ivan Marchionni, Virág T. Takács, Maria Grazia Nunzi, Enrico Mugnaini, Richard J. Miller, Gianmaria Maccaferri
    Abstract:

    The CXC chemokine receptor 4 (CXCR4) for the chemokine (C-X-C motif) ligand 12/stromal cell-derived factor-1 α (CXCL12/SDF-1 α) is highly expressed in the postnatal CA1 Stratum Lacunosum-Moleculare. However, both the network events triggered by SDF-1 α in this microcircuit and the cellular targets of this chemokine remain virtually unexplored. Here, we have studied SDF-1 α-mediated neuromodulation of the Stratum Lacunosum-Moleculare by directly comparing the properties of CXCR4-expressing Cajal–Retzius cells vs. CXCR4-non-expressing interneurons, and by recording the electrophysiological effects caused by application of SDF-1 α on either cell type. We demonstrate that SDF-1 α dramatically reduces spontaneous firing in Cajal–Retzius cells via hyerpolarization, and that cessation of firing is prevented by the CXCR4-specific antagonist AMD3100. In contrast, no effects on the excitability of interneurons of the same layer were observed following exposure to the chemokine. We also provide evidence that, despite the expression of functional glutamate receptors, Cajal–Retzius cells are integrated in the synaptic network of the Stratum Lacunosum-Moleculare via excitatory GABAergic input. Furthermore, we show that the axons of Cajal–Retzius cells target specifically the Stratum Lacunosum-Moleculare and the dentate gyrus, but lack postsynaptic specializations opposite to their axonal varicosities. These results, taken together with our observation that SDF-1 α reduces evoked field responses at the entorhinal cortex–CA1 synapse, suggest that Cajal–Retzius cells produce a diffuse output that may impact information processing of Stratum Lacunosum-Moleculare. We propose that pathological alterations of local levels of SDF-1 α or CXCR4 expression may affect the functions of an important hippocampal microcircuit.

  • Distinctive properties of CXC chemokine receptor 4-expressing Cajal-Retzius cells versus GABAergic interneurons of the postnatal hippocampus.
    The Journal of physiology, 2010
    Co-Authors: Ivan Marchionni, Virág T. Takács, Maria Grazia Nunzi, Enrico Mugnaini, Richard J. Miller, Gianmaria Maccaferri
    Abstract:

    The CXC chemokine receptor 4 (CXCR4) for the chemokine (C-X-C motif) ligand 12/stromal cell-derived factor-1 alpha (CXCL12/SDF-1 alpha) is highly expressed in the postnatal CA1 Stratum Lacunosum-Moleculare. However, both the network events triggered by SDF-1 alpha in this microcircuit and the cellular targets of this chemokine remain virtually unexplored. Here, we have studied SDF-1 alpha-mediated neuromodulation of the Stratum Lacunosum-Moleculare by directly comparing the properties of CXCR4-expressing Cajal-Retzius cells vs. CXCR4-non-expressing interneurons, and by recording the electrophysiological effects caused by application of SDF-1 alpha on either cell type. We demonstrate that SDF-1 alpha dramatically reduces spontaneous firing in Cajal-Retzius cells via hyerpolarization, and that cessation of firing is prevented by the CXCR4-specific antagonist AMD3100. In contrast, no effects on the excitability of interneurons of the same layer were observed following exposure to the chemokine. We also provide evidence that, despite the expression of functional glutamate receptors, Cajal-Retzius cells are integrated in the synaptic network of the Stratum Lacunosum-Moleculare via excitatory GABAergic input. Furthermore, we show that the axons of Cajal-Retzius cells target specifically the Stratum Lacunosum-Moleculare and the dentate gyrus, but lack postsynaptic specializations opposite to their axonal varicosities. These results, taken together with our observation that SDF-1 alpha reduces evoked field responses at the entorhinal cortex-CA1 synapse, suggest that Cajal-Retzius cells produce a diffuse output that may impact information processing of Stratum Lacunosum-Moleculare. We propose that pathological alterations of local levels of SDF-1 alpha or CXCR4 expression may affect the functions of an important hippocampal microcircuit.

Imre Vida - One of the best experts on this subject based on the ideXlab platform.

  • Unitary IPSPs evoked by interneurons at the Stratum radiatum-Stratum Lacunosum-Moleculare border in the CA1 area of the rat hippocampus in vitro.
    The Journal of physiology, 1998
    Co-Authors: Imre Vida, K. Halasy, Csaba Szinyei, P Somogyi, Eberhard H. Buhl
    Abstract:

    1. Hippocampal non-principal neurons at the Stratum radiatum-Stratum Lacunosum-Moleculare border (R-LM interneurons) of the CA1 area may constitute several cell classes and have been implicated in the generation of GABAergic unitary IPSPs. Using biocytin-filled electrodes we recorded R-LM interneurons intracellularly in vitro and determined their postsynaptic effects in concomitantly recorded pyramidal cells. 2. Light microscopic analysis revealed four populations of R-LM interneurons with distinct axons: (1) basket cells (n = 4) with axons predominantly ramifying in the pyramidal cell layer; (2) Schaffer collateral/commissural pathway-associated interneurons (n = 10) stratifying in Stratum radiatum and, to a lesser extent, Stratum oriens; (3) perforant pathway-associated interneurons (n = 6) innervating the perforant path termination zone in Stratum Lacunosum-Moleculare of the CA1 area as well as equivalent portions of the dentate gyrus and subiculum; and (4) neurogliaform interneurons (n = 2) characterized by their dense, compact axonal and dendritic arbour. 3. Random electron microscopic sampling of synaptic targets revealed a preponderance of pyramidal neurons as postsynaptic elements. Basket cells had a synaptic target preference for somata and proximal dendrites, whereas the remainder of R-LM interneurons innervated dendritic shafts and spines. The axon of dendrite-targeting cells formed up to six putative contacts with individual postsynatpic pyramidal cells. 4. Anatomically recovered R-LM interneurons (n = 22) had a mean resting membrane potential of -56.7 +/- 3.6 mV, a membrane time constant of 12.9 +/- 7.7 ms and an input resistance of 86.4 +/- 29.2 M omega. Depolarizing current pulses generally elicited overshooting action potentials (70.8 +/- 6.9 mV) which had a mean duration, when measured at half-amplitude, of 0.7 +/- 0.1 ms. In response to prolonged (> 200 ms) depolarizing current pulses all R-LM interneurons displayed (a varying degree of) spike frequency adaptation. 5. Basket cells, Schaffer-associated and neurogliaform interneurons elicited small-amplitude (< 2 mV), short-latency IPSPs in postsynaptic pyramids (n = 5, 13 and 1, respectively). Those interactions in which an effect was elicited with the repetitive activation of the presynaptic neuron (n = 13) showed a substantial degree of postsynaptic response summation. Unitary IPSPs had fast kinetics and, whenever tested (n = 5; 1 basket cell and 4 Schaffer-associated interneurons), were abolished by the GABAA receptor antagonist bicuculline. 6. Thus, R-LM interneurons comprise several distinct populations which evoke fast GABAA receptor mediated IPSPs. The domain-specific innervation of postsynaptic pyramidal cells suggests functionally diverse effects on the integration of afferent information in functionally non-equivalent compartments of pyramidal cells.

  • Unitary IPSPs evoked by interneurons at the Stratum radiatum‐Stratum Lacunosum‐Moleculare border in the CA1 area of the rat hippocampus in vitro
    The Journal of Physiology, 1998
    Co-Authors: Imre Vida, Peter Somogyi, K. Halasy, Csaba Szinyei, Eberhard H. Buhl
    Abstract:

    1. Hippocampal non-principal neurons at the Stratum radiatum-Stratum Lacunosum-Moleculare border (R-LM interneurons) of the CA1 area may constitute several cell classes and have been implicated in the generation of GABAergic unitary IPSPs. Using biocytin-filled electrodes we recorded R-LM interneurons intracellularly in vitro and determined their postsynaptic effects in concomitantly recorded pyramidal cells. 2. Light microscopic analysis revealed four populations of R-LM interneurons with distinct axons: (1) basket cells (n = 4) with axons predominantly ramifying in the pyramidal cell layer; (2) Schaffer collateral/commissural pathway-associated interneurons (n = 10) stratifying in Stratum radiatum and, to a lesser extent, Stratum oriens; (3) perforant pathway-associated interneurons (n = 6) innervating the perforant path termination zone in Stratum Lacunosum-Moleculare of the CA1 area as well as equivalent portions of the dentate gyrus and subiculum; and (4) neurogliaform interneurons (n = 2) characterized by their dense, compact axonal and dendritic arbour. 3. Random electron microscopic sampling of synaptic targets revealed a preponderance of pyramidal neurons as postsynaptic elements. Basket cells had a synaptic target preference for somata and proximal dendrites, whereas the remainder of R-LM interneurons innervated dendritic shafts and spines. The axon of dendrite-targeting cells formed up to six putative contacts with individual postsynatpic pyramidal cells. 4. Anatomically recovered R-LM interneurons (n = 22) had a mean resting membrane potential of -56.7 +/- 3.6 mV, a membrane time constant of 12.9 +/- 7.7 ms and an input resistance of 86.4 +/- 29.2 M omega. Depolarizing current pulses generally elicited overshooting action potentials (70.8 +/- 6.9 mV) which had a mean duration, when measured at half-amplitude, of 0.7 +/- 0.1 ms. In response to prolonged (> 200 ms) depolarizing current pulses all R-LM interneurons displayed (a varying degree of) spike frequency adaptation. 5. Basket cells, Schaffer-associated and neurogliaform interneurons elicited small-amplitude (< 2 mV), short-latency IPSPs in postsynaptic pyramids (n = 5, 13 and 1, respectively). Those interactions in which an effect was elicited with the repetitive activation of the presynaptic neuron (n = 13) showed a substantial degree of postsynaptic response summation. Unitary IPSPs had fast kinetics and, whenever tested (n = 5; 1 basket cell and 4 Schaffer-associated interneurons), were abolished by the GABAA receptor antagonist bicuculline. 6. Thus, R-LM interneurons comprise several distinct populations which evoke fast GABAA receptor mediated IPSPs. The domain-specific innervation of postsynaptic pyramidal cells suggests functionally diverse effects on the integration of afferent information in functionally non-equivalent compartments of pyramidal cells.

E W Lothman - One of the best experts on this subject based on the ideXlab platform.

  • Changes in inhibitory neurotransmission in the CA1 region and dentate gyrus in a chronic model of temporal lobe epilepsy.
    Journal of neurophysiology, 1995
    Co-Authors: P S Mangan, D A Rempe, E W Lothman
    Abstract:

    1. In this report we compare changes in inhibitory neurotransmission within the CA1 region and the dentate gyrus (DG) in a model of chronic temporal lobe epilepsy (TLE). Extracellular and intracellular recordings were obtained in combined hippocampal-parahippocampal slices > or = 1 mo after a period of self-sustaining limbic status epilepticus (SSLSE) induced by continuous hippocampal stimulation. 2. Polysynaptic inhibitory postsynaptic potentials (IPSPs) were induced by positioning electrodes to activate specific afferent pathways and evoking responses in the absence of glutamate receptor antagonists [D(-)-2-amino-5-phosphonovaleric acid (APV) and 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX)]. Polysynaptic IPSPs were evoked in CA1 pyramidal cells from electrodes positioned in Stratum radiatum and in Stratum Lacunosum/Moleculare. Polysynaptic IPSPs were evoked in DG granule cells from electrodes positioned over the perforant path located in the subiculum. Monosynaptic IPSPs were induced by positioning electrodes within 200 microns of the intracellular recording electrode (near site stimulation) and stimulating in the presence of APV and CNQX to block ionotropic glutamate receptors. Monosynaptic IPSPs were evoked in CA1 pyramidal cells with electrodes positioned in the Stratum Lacunosum/Moleculare and Stratum pyramidale. Monosynaptic IPSPs were evoked in DG granule cells with electrodes positioned in the Stratum Moleculare. 3. Population spike (PS) amplitudes were employed to assure that a full range of stimulus strengths, from subthreshold for action potentials to an intensity giving maximal-amplitude PSs, was used to elicit polysynaptic IPSPs in CA1 pyramidal cells in both post-SSLSE and control slices. In control tissue, polysynaptic IPSPs were biphasic, composed of early and late events. In post-SSLSE tissue, polysynaptic IPSPs were markedly diminished. The diminution of polysynaptic IPSPs was detected at all levels of stimulus intensity. Both early IPSPs [mediated by gamma-aminobutyric acid-A (GABAA) receptors] and late IPSPs (mediated by GABAB receptors) were diminished. Polysynaptic IPSPs were diminished with both Stratum radiatum and with Stratum Lacunosum/Moleculare stimulation. 4. Reversal potentials for either polysynaptic early or polysynaptic late IPSPs evoked in CA1 pyramidal cells by Stratum radiatum stimulation were not different in slices from post-SSLSE animals as compared with control animals. Likewise, reversal potentials for either polysynaptic early or polysynaptic late IPSPs evoked by Stratum Lacunosum/Moleculare stimulation did not differ in the two groups. These findings excluded changes in driving force as an explanation for the diminished amplitude of IPSPs in CA1 pyramidal cells in the post-SSLSE model.(ABSTRACT TRUNCATED AT 400 WORDS)

  • Spreading depression and reverberatory seizures induce the upregulation of mRNA for glial fibrillary acidic protein.
    Brain research, 1994
    Co-Authors: D J Bonthius, E W Lothman, J L Stringer, O Steward
    Abstract:

    The present study evaluates the relative roles of seizure activity and spreading depression in upregulating glial fibrillary acidic protein (GFAP) mRNA expression. Stimulating electrodes were placed bilaterally in the angular bundle, and recording electrodes were placed bilaterally in the dentate gyrus of adult rats. Intense electrographic seizures were induced by delivering stimulus trains through one stimulating electrode. In some cases, spreading depression accompanied the seizures, while in other cases, the seizures occurred in the absence of spreading depression. Animals were killed 24 h following the last stimulus train, and the forebrains were prepared for quantitative in situ hybridization. Seizure activity and spreading depression led to significant increases in GFAP mRNA levels in the hippocampal formation. Seizure activity alone (without spreading depression) induced a 4-fold increase in GFAP mRNA levels in the hilus and molecular layer of the dentate gyrus and in Stratum Lacunosum-Moleculare of the hippocampus. When seizure activity was accompanied by spreading depression, there was a 10-fold increase in GFAP mRNA levels in these same regions. Regional differences within the hippocampal formation in glial cell response were evident. While GFAP mRNA levels in Stratum Lacunosum-Moleculare of the hippocampus were upregulated by seizure activity and spreading depression, levels in hippocampal Stratum radiatum of the hippocampus remained unchanged. The results suggest that abnormal neuronal activity can influence glial cell gene expression and that spreading depression is a stronger signal than seizure activity in upregulating GFAP mRNA levels.

Michael E. Hasselmo - One of the best experts on this subject based on the ideXlab platform.

  • Difference in time course of modulation of synaptic transmission by group II versus group III metabotropic glutamate receptors in region CA1 of the hippocampus.
    Hippocampus, 2006
    Co-Authors: Lisa M. Giocomo, Michael E. Hasselmo
    Abstract:

    We investigated the time course of modulation of synaptic transmission by group II and group III metabotropic glutamate receptors in region CA1 of the hippocampus. In the presence of 50 mM picrotoxin, pressure pulse application of 1 mM glutamate resulted in a fast onset of suppression of synaptic transmission in Stratum Lacunosum Moleculare and a slower onset of suppression in Stratum radiatum, with both effects returning to baseline over the course of several minutes. Application of 50 mM of the group II agonist (2R,4R)-APDC in Stratum Lacunosum molec- ulare resulted in the same fast onset of suppression while having no effect in Stratum radiatum. Pressure pulse application of 100 m MD L-AP4 in stra- tum Lacunosum Moleculare and Stratum radiatum resulted in a much slower onset of suppression of synaptic transmission than (2R,4R)-APDC. Suppression by (2R,4R)-APDC was accompanied by a rapid enhancement of paired pulse facilitation, indicative of a presynaptic mechanism. This demonstrates that activation of group II mGluRs in the hippocampus causes a fast onset of suppression in Stratum Lacunosum Moleculare, while activation of group III mGluRs causes a slower onset of suppression. The difference in time course for group II vs. group III mGluRs suggests a dif- ferent functional role, with group II playing a potential role in making syn- apses act as low pass filters. V C 2006 Wiley-Liss, Inc.

  • Theta rhythmic stimulation of Stratum Lacunosum-Moleculare in rat hippocampus contributes to associative LTP at a phase offset in Stratum radiatum.
    Journal of neurophysiology, 2004
    Co-Authors: Sarah J. Judge, Michael E. Hasselmo
    Abstract:

    Computational modeling demonstrates that encoding and context-dependent retrieval of memories in region CA1 of the hippocampus will be most effective when the phase of strongest entorhinal input (to Stratum Lacunosum-Moleculare) is offset from the phase of maximal induction of long-term potentiation at Schaffer collateral synapses (in s. radiatum). This would allow entorhinal input to play a role in both retrieval and encoding without engaging long-term potentiation (LTP) during retrieval. Experiments in brain slice preparations of the hippocampal formation tested the relationship between rhythmic input to s. Lacunosum-Moleculare and the time of maximal LTP induction at Schaffer collateral synapses in s. radiatum. Analysis of the data demonstrates a statistically significant difference in the induction of LTP for different time intervals between the end of each four-pulse train in s. Lacunosum-Moleculare and the single pulse s. radiatum stimulation. The time of maximal LTP induction was found to be ∼30 ms after the end of Lacunosum-Moleculare stimulation, consistent with the requirements of the model.