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

  • Sharp Wave-Like Activity in the Hippocampus In Vitro in Mice Lacking the Gap Junction Protein Connexin 36
    Journal of neurophysiology, 2003
    Co-Authors: Isabel Pais, Eberhard H. Buhl, Sheriar G. Hormuzdi, Hannah Monyer, Roger D. Traub, Ian C. Wood, Miles A. Whittington, Fiona E. N. Lebeau
    Abstract:

    Bath application of kainate (100–300 nM) induced a persistent gamma-frequency (30–80 Hz) oscillation that could be recorded in Stratum Radiatum of the CA3 region in vitro. We have previously descri...

  • 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.

Eric Hanse - One of the best experts on this subject based on the ideXlab platform.

  • The endogenous peptide antisecretory factor promotes tonic GABAergic signaling in CA1 Stratum Radiatum interneurons
    Frontiers in cellular neuroscience, 2014
    Co-Authors: Joakim Strandberg, Catarina Lindquist, Stefan Lange, Fredrik Asztely, Eric Hanse
    Abstract:

    Tonic GABAergic inhibition regulates neuronal excitability and has been implicated to be involved in both neurological and psychiatric diseases. We have previously shown that the endogenous peptide antisecretory factor (AF) decreases phasic GABAergic inhibition onto pyramidal CA1 neurons. In the present study, using whole-cell patch-clamp recordings, we investigated the mechanisms behind this disinhibition of CA1 pyramidal neurons by AF. We found that application of AF to acute rat hippocampal slices resulted in a reduction of the frequency, but not of the amplitude, of spontaneous inhibitory postsynaptic currents (sIPSCs) in CA1 pyramidal neurons. Miniature inhibitory postsynaptic currents (mIPSCs), recorded in the presence of tetrodotoxin (TTX), were however not affected by AF, neither in CA1 pyramidal cells, nor in Stratum Radiatum interneurons. Instead, AF caused an increase of the tonic GABAA current in Stratum Radiatum interneurons, leaving the tonic GABAergic transmission in CA1 pyramidal cells unaffected. These results show that the endogenous peptide AF enhances tonic, but not phasic, GABAergic signaling in CA1 Stratum Radiatum interneurons, without affecting tonic GABAergic signaling in CA1 pyramidal neurons. We suggest that this increased tonic GABAergic signaling in GABAergic interneurons could be a mechanism for the AF-mediated disinhibition of pyramidal neurons.

  • Development of synaptic connectivity onto interneurons in Stratum Radiatum in the CA1 region of the rat hippocampus
    BMC Neuroscience, 2012
    Co-Authors: Ilse Riebe, Eric Hanse
    Abstract:

    Background The impact of a given presynaptic neuron on the firing probability of the postsynaptic neuron critically depends on the number of functional release sites that connect the two neurons. One way of determining the average functional synaptic connectivity onto a postsynaptic neuron is to compare the amplitudes of action potential dependent spontaneous synaptic currents with the amplitude of the synaptic currents that are independent of action potentials ("minis"). With this method it has been found that average synaptic connectivity between glutamatergic CA3 and CA1 pyramidal cells increases from single connections in the neonatal rat, to multiple connections in the young adult rat. On the other hand, γ-aminobutyric acid (GABA)ergic interneurons form multiple connections onto CA1 pyramidal cells already in the neonatal rat, and the degree of multiple GABAergic connectivity is preserved into adulthood. In the present study, we have examined the development of glutamate and GABA connectivity onto GABAergic CA1 Stratum Radiatum interneurons in the hippocampal slice, and compared this to the connectivity onto CA1 pyramidal neurons. Results In GABAergic interneurons in the CA1 Stratum Radiatum, irrespective of developmental stage, we found that the average amplitude of action potential dependent spontaneous AMPA receptor-mediated synaptic currents were of the same magnitude as the mini AMPA receptor mediated synaptic currents. This finding indicates that these GABAergic interneurons, in contrast to the CA1 pyramidal neurons, preserve single glutamate connectivity throughout development. For GABA connectivity, on the other hand, we found multiple functional synaptic connections onto the interneurons, as onto the pyramidal cells. Conclusions The results presented here confirm that glutamate and GABA synaptic connectivity develop very differently in the hippocampal CA1 region. Thus, whereas average GABA connectivity is multiple throughout the development, glutamate connectivity is unitary early in development. Our results further suggest that the development of glutamate synaptic connectivity differs markedly between pyramidal cells and GABAergic interneurons in Stratum Radiatum, such that a given presynaptic glutamatergic cell appears not allowed to increase its connectivity onto the postsynaptic Stratum Radiatum interneuron, as it may do onto the postsynaptic CA1 pyramidal cell.

  • Development of synaptic connectivity onto interneurons in Stratum Radiatum in the CA1 region of the rat hippocampus.
    BMC neuroscience, 2012
    Co-Authors: Ilse Riebe, Eric Hanse
    Abstract:

    Background The impact of a given presynaptic neuron on the firing probability of the postsynaptic neuron critically depends on the number of functional release sites that connect the two neurons. One way of determining the average functional synaptic connectivity onto a postsynaptic neuron is to compare the amplitudes of action potential dependent spontaneous synaptic currents with the amplitude of the synaptic currents that are independent of action potentials ("minis"). With this method it has been found that average synaptic connectivity between glutamatergic CA3 and CA1 pyramidal cells increases from single connections in the neonatal rat, to multiple connections in the young adult rat. On the other hand, γ-aminobutyric acid (GABA)ergic interneurons form multiple connections onto CA1 pyramidal cells already in the neonatal rat, and the degree of multiple GABAergic connectivity is preserved into adulthood. In the present study, we have examined the development of glutamate and GABA connectivity onto GABAergic CA1 Stratum Radiatum interneurons in the hippocampal slice, and compared this to the connectivity onto CA1 pyramidal neurons.

  • Silent synapses onto interneurons in the rat CA1 Stratum Radiatum.
    The European journal of neuroscience, 2009
    Co-Authors: Ilse Riebe, Bengt Gustafsson, Eric Hanse
    Abstract:

    Glutamate transmission to gamma-aminobutyric acid (GABA)ergic interneurons and to principal neurons differs in various important respects. Whether these differences exist from an early developmental stage, or result from differential development from a more common state, is unclear. In the hippocampal CA1 area, glutamate transmission to the developing, but not to the adult, principal neurons is characterized by the presence of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) silent synapses and of AMPA silencing induced by test pulse stimulation (0.03-1 Hz). In the present study, we examined whether this developmental difference in AMPA signaling is also true for glutamate transmission to CA1 Stratum Radiatum interneurons. We found that AMPA silent synapses onto these interneurons also exist, and that they can be generated by test pulse stimulation. In marked contrast to AMPA silencing in principal neurons, AMPA silencing in interneurons was not developmentally restricted, but was observed to the same extent after the first postnatal month as in the second postnatal week. In addition, we found that glutamate synapses onto these interneurons can also be N-methyl-d-aspartate (NMDA)-silent, that is, only AMPA-signaling. After test pulse stimulation, the AMPA-silent, the NMDA-silent and the AMPA/NMDA-signaling synapses onto the developing interneurons were estimated to be about equally frequent. These results highlight a diversity of glutamate signaling to CA1 Stratum Radiatum interneurons, and they indicate that the glutamate synapses onto pyramidal neurons and to interneurons can mature differentially.

Jens Ledet Jensen - One of the best experts on this subject based on the ideXlab platform.

  • synaptic contact number and size in Stratum Radiatum ca1 of app ps1δe9 transgenic mice
    Neurobiology of Aging, 2009
    Co-Authors: Mark J. West, Georg Bach, Andreas Søderman, Jens Ledet Jensen
    Abstract:

    Synaptic changes occur early in the course of Alzheimer's disease and are key to understanding the initial events in associated neurodegenerative processes. The quantitative analysis of synaptic morphology in transgenic mouse models of Alzheimer's disease can provide important insights into these processes. To this end, the total number and the distribution of the diameters of synaptic contacts in the Stratum Radiatum of the CA1 region of the hippocampus of 12-month-old APP/PS1ΔE9 transgenic mice and wild type littermates have been evaluated by applying design-based stereological methods to material prepared for electron microscopy. Although there were no differences in the size of the synaptic contacts, the total number of synaptic contacts was significantly larger in the transgenic mice, suggesting that the transgenic effect at this age is synaptotrophic and that the presence of amyloid plaques and an elevated Abeta42/40 ratio are not necessarily detrimental to populations of synapses. The potential of this type of data in evaluating synaptic changes related to Alzheimer's disease is discussed and the methodology described in detail.

  • Synaptic contact number and size in Stratum Radiatum CA1 of APP/PS1ΔE9 transgenic mice
    Neurobiology of aging, 2008
    Co-Authors: Mark J. West, Georg Bach, Andreas Søderman, Jens Ledet Jensen
    Abstract:

    Synaptic changes occur early in the course of Alzheimer's disease and are key to understanding the initial events in associated neurodegenerative processes. The quantitative analysis of synaptic morphology in transgenic mouse models of Alzheimer's disease can provide important insights into these processes. To this end, the total number and the distribution of the diameters of synaptic contacts in the Stratum Radiatum of the CA1 region of the hippocampus of 12-month-old APP/PS1ΔE9 transgenic mice and wild type littermates have been evaluated by applying design-based stereological methods to material prepared for electron microscopy. Although there were no differences in the size of the synaptic contacts, the total number of synaptic contacts was significantly larger in the transgenic mice, suggesting that the transgenic effect at this age is synaptotrophic and that the presence of amyloid plaques and an elevated Abeta42/40 ratio are not necessarily detrimental to populations of synapses. The potential of this type of data in evaluating synaptic changes related to Alzheimer's disease is discussed and the methodology described in detail.

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.

Ilse Riebe - One of the best experts on this subject based on the ideXlab platform.

  • Development of synaptic connectivity onto interneurons in Stratum Radiatum in the CA1 region of the rat hippocampus.
    BMC neuroscience, 2012
    Co-Authors: Ilse Riebe, Eric Hanse
    Abstract:

    Background The impact of a given presynaptic neuron on the firing probability of the postsynaptic neuron critically depends on the number of functional release sites that connect the two neurons. One way of determining the average functional synaptic connectivity onto a postsynaptic neuron is to compare the amplitudes of action potential dependent spontaneous synaptic currents with the amplitude of the synaptic currents that are independent of action potentials ("minis"). With this method it has been found that average synaptic connectivity between glutamatergic CA3 and CA1 pyramidal cells increases from single connections in the neonatal rat, to multiple connections in the young adult rat. On the other hand, γ-aminobutyric acid (GABA)ergic interneurons form multiple connections onto CA1 pyramidal cells already in the neonatal rat, and the degree of multiple GABAergic connectivity is preserved into adulthood. In the present study, we have examined the development of glutamate and GABA connectivity onto GABAergic CA1 Stratum Radiatum interneurons in the hippocampal slice, and compared this to the connectivity onto CA1 pyramidal neurons.

  • Development of synaptic connectivity onto interneurons in Stratum Radiatum in the CA1 region of the rat hippocampus
    BMC Neuroscience, 2012
    Co-Authors: Ilse Riebe, Eric Hanse
    Abstract:

    Background The impact of a given presynaptic neuron on the firing probability of the postsynaptic neuron critically depends on the number of functional release sites that connect the two neurons. One way of determining the average functional synaptic connectivity onto a postsynaptic neuron is to compare the amplitudes of action potential dependent spontaneous synaptic currents with the amplitude of the synaptic currents that are independent of action potentials ("minis"). With this method it has been found that average synaptic connectivity between glutamatergic CA3 and CA1 pyramidal cells increases from single connections in the neonatal rat, to multiple connections in the young adult rat. On the other hand, γ-aminobutyric acid (GABA)ergic interneurons form multiple connections onto CA1 pyramidal cells already in the neonatal rat, and the degree of multiple GABAergic connectivity is preserved into adulthood. In the present study, we have examined the development of glutamate and GABA connectivity onto GABAergic CA1 Stratum Radiatum interneurons in the hippocampal slice, and compared this to the connectivity onto CA1 pyramidal neurons. Results In GABAergic interneurons in the CA1 Stratum Radiatum, irrespective of developmental stage, we found that the average amplitude of action potential dependent spontaneous AMPA receptor-mediated synaptic currents were of the same magnitude as the mini AMPA receptor mediated synaptic currents. This finding indicates that these GABAergic interneurons, in contrast to the CA1 pyramidal neurons, preserve single glutamate connectivity throughout development. For GABA connectivity, on the other hand, we found multiple functional synaptic connections onto the interneurons, as onto the pyramidal cells. Conclusions The results presented here confirm that glutamate and GABA synaptic connectivity develop very differently in the hippocampal CA1 region. Thus, whereas average GABA connectivity is multiple throughout the development, glutamate connectivity is unitary early in development. Our results further suggest that the development of glutamate synaptic connectivity differs markedly between pyramidal cells and GABAergic interneurons in Stratum Radiatum, such that a given presynaptic glutamatergic cell appears not allowed to increase its connectivity onto the postsynaptic Stratum Radiatum interneuron, as it may do onto the postsynaptic CA1 pyramidal cell.

  • Silent synapses onto interneurons in the rat CA1 Stratum Radiatum.
    The European journal of neuroscience, 2009
    Co-Authors: Ilse Riebe, Bengt Gustafsson, Eric Hanse
    Abstract:

    Glutamate transmission to gamma-aminobutyric acid (GABA)ergic interneurons and to principal neurons differs in various important respects. Whether these differences exist from an early developmental stage, or result from differential development from a more common state, is unclear. In the hippocampal CA1 area, glutamate transmission to the developing, but not to the adult, principal neurons is characterized by the presence of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) silent synapses and of AMPA silencing induced by test pulse stimulation (0.03-1 Hz). In the present study, we examined whether this developmental difference in AMPA signaling is also true for glutamate transmission to CA1 Stratum Radiatum interneurons. We found that AMPA silent synapses onto these interneurons also exist, and that they can be generated by test pulse stimulation. In marked contrast to AMPA silencing in principal neurons, AMPA silencing in interneurons was not developmentally restricted, but was observed to the same extent after the first postnatal month as in the second postnatal week. In addition, we found that glutamate synapses onto these interneurons can also be N-methyl-d-aspartate (NMDA)-silent, that is, only AMPA-signaling. After test pulse stimulation, the AMPA-silent, the NMDA-silent and the AMPA/NMDA-signaling synapses onto the developing interneurons were estimated to be about equally frequent. These results highlight a diversity of glutamate signaling to CA1 Stratum Radiatum interneurons, and they indicate that the glutamate synapses onto pyramidal neurons and to interneurons can mature differentially.