The Experts below are selected from a list of 1572 Experts worldwide ranked by ideXlab platform

Jeanclaude Lacaille - One of the best experts on this subject based on the ideXlab platform.

  • synaptically activated calcium responses in dendrites of hippocampal Oriens alveus interneurons
    Journal of Neurophysiology, 2001
    Co-Authors: Christine E Gee, Gavin L Woodhall, Jeanclaude Lacaille
    Abstract:

    Activation of metabotropic glutamate receptors (mGluRs) by agonists increases intracellular calcium levels ([Ca2+]i) in interneurons of Stratum Oriens/alveus (OA) of the hippocampus. We examined th...

  • membrane potential and intracellular ca2 oscillations activated by mglurs in hippocampal Stratum Oriens alveus interneurons
    Journal of Neurophysiology, 1999
    Co-Authors: Gavin L Woodhall, Christine E Gee, Richard Robitaille, Jeanclaude Lacaille
    Abstract:

    Woodhall, Gavin, Christine E. Gee, Richard Robitaille, and Jean-Claude Lacaille. Membrane potential and intracellular Ca2+ oscillations activated by mGluRs in hippocampal Stratum Oriens/alveus inte...

  • mechanisms of selective long term potentiation of excitatory synapses in Stratum Oriens alveus interneurons of rat hippocampal slices
    Journal of Neurophysiology, 1995
    Co-Authors: Mohamed Ouardouz, Jeanclaude Lacaille
    Abstract:

    1. We investigated long-term potentiation (LTP) of synaptic transmission in different populations of interneurons in the CA1 region of rat hippocampal slices using whole cell recordings. We elicited excitatory postsynaptic currents (EPSCs) in interneurons located in Stratum Oriens near the alveus (O/A) or in Stratum lacunosum-moleculare near the Stratum radiatum border (L-M) by electrical stimulation of nearby axons in Stratum Oriens and radiatum, respectively. 2. High-frequency stimulation (100 Hz, 1 s) of axons in conjunction with postsynaptic depolarization (to -20 mV) increased the peak amplitude of test EPSCs elicited at -80 mV in O/A interneurons. The mean peak amplitude of EPSCs was significantly potentiated relative to the control period at 10 min (39 +/- 7% increase, mean +/- SE; n = 11 cells) and 30 min (30 +/- 1% increase; n = 5 cells) after tetanization. Similar stimulation did not produce potentiation of EPSCs in L-M interneurons (n = 7 cells). 3. This selective LTP in O/A interneurons was reversibly blocked by the N-methyl-D-aspartate receptor antagonist (+/-)2-amino-5-phosphonopentanoic acid (AP-5). Tetanization in the presence of 25 microM AP-5 did not increase the amplitude of EPSCs (8 cells). After washout of AP-5 (4 cells), a second tetanization resulted in long-term potentiation of EPSCs. 4. LTP was dependent on the activation of metabotropic glutamate receptors. The peak amplitude of EPSCs was not increased 5-10 or 15-20 min after tetanization during bath application of the metabotropic glutamate receptor antagonist (RS)-alpha-methyl-4-carboxyphenylglycine (500 microM) (n = 5 cells). 5. Inclusion of the Ca2+ chelator 1,2-bis(2-aminophenoxy)-ethane-N,N,N',N'-tetraacetic acid (BAPTA; 25 mM) in the patch pipette blocked LTP in O/A interneurons. In five cells recorded with BAPTA-containing electrodes, the mean peak amplitude was not significantly increased after tetanization. Thus a rise in postsynaptic intracellular Ca2+ appeared necessary for the induction of LTP in these interneurons. 6. Incubation of slices with the inhibitor of nitric oxide synthase N omega-nitro-L-arginine methyl ester (100 microM) before and throughout the recording session also blocked the increase in EPSC amplitude at 5-10 min (5 cells) and 15-20 min (3 cells) after tetanization. NO synthesis may therefore be necessary for LTP in O/A interneurons. 7. These results suggest that LTP of excitatory synapses is selectively produced in O/A but not L-M interneurons, and that this LTP shares similar characteristics with LTP in hippocampal CA1 pyramidal cells.(ABSTRACT TRUNCATED AT 400 WORDS)

Chris J Mcbain - One of the best experts on this subject based on the ideXlab platform.

  • the hyperpolarization activated current ih and its contribution to pacemaker activity in rat ca1 hippocampal Stratum Oriens alveus interneurones
    The Journal of Physiology, 1996
    Co-Authors: Gianmaria Maccaferri, Chris J Mcbain
    Abstract:

    1. The hyperpolarization-activated current (Ih) and its role in pacemaking activity in rat hippocampal Stratum Oriens-alveus interneurones was studied using whole-cell and perforated patch-clamp configurations. 2. Voltage-clamp recordings revealed Ih as a slowly activating, inward current, activated by hyperpolarizing steps (holding potential, Vh = -40 mV), with a reversal potential close to -30 mV. Its activation curve ranged from approximately -50 to -120 mV with a mid-activation point of -84.1 mV. 3. Ih was blocked by external application of Cs+ (2-5 mM) and ZD7288 (100 microM), but not by Ba2+ (1 mM). 4. Ih was potentiated by both noradrenaline and isoprenaline by a mechanism consistent with a shift in the Ih activation curve. 5. Under current-clamp conditions (Vh = -60 mV), ZD7288 induced a membrane hyperpolarization concomitant with an increase in the membrane input resistance and abolished the voltage sag generated by hyperpolarizing current injection. 6. Analysis of the current-discharge relationship revealed that block of Ih differentially increased the firing frequency of spikes occurring early in the train compared with those occurring late in the discharge. 7. When applied to spontaneously firing cells, ZD7288 reduced the firing frequency by selectively altering the time course of the interspike interval, while minimally affecting other action potential characteristics. Similarly, isoprenaline increased the spontaneous firing frequency by an effect exclusively on the after-hyperpolarization and interspike interval. 8. These results provide evidence for the involvement of Ih in the excitability and generation of spontaneous firing in hippocampal Stratum Oriens-alveus interneurones.

  • voltage gated potassium currents in Stratum Oriens alveus inhibitory neurones of the rat ca1 hippocampus
    The Journal of Physiology, 1995
    Co-Authors: Li Zhang, Chris J Mcbain
    Abstract:

    1. Voltage-activated K+ currents were recorded from visually identified inhibitory interneurones of the CA1 Stratum Oriens-alveus region in neonatal rat hippocampal slices using outside-out patch and whole-cell voltage clamp techniques. 2. Outward currents comprised both a transient and a sustained component when elicited from a holding potential of -90 mV. Tail current analysis of current reversal potentials showed that outward currents were carried by potassium ions. 3. The transient current, IA, was activated with a time to peak within 5 ms, inactivated with a time constant of approximately 15 ms at 0 mV and possessed half-activation at -14 mV. Half-inactivation of the transient current occurred at -71 mV. At -90 mV, the transient current recovered from inactivation with a time constant of 142 ms. 4. Activation of currents from a holding potential of -50 mV permitted isolation of the sustained current, IK. In Ca(2+)-free conditions the sustained current showed rapid activation, reaching about 80% of its maximum within 1.5 ms, and showed little inactivation during 1 s depolarizing steps. The majority of sustained outward currents showed no voltage-dependent inactivation. In approximately 20% of cells, a slow time-dependent inactivation of the sustained current was observed, suggesting the presence of a second type of sustained current in these cells. 5. A Ca(2+)-dependent K+ current comprised a significant portion of the total sustained current; this current was activated at voltages positive to -30 mV and showed no time-dependent inactivation over a 1 s depolarizing step. This current component was removed in Ca(2+)-free conditions or by iberiotoxin. 6. Low concentrations of 4-AP (50 microM) attenuated both the transient and sustained current components recorded in a Ca(2+)-free solution. Higher concentrations of 4-AP (< 10 mM) were without further effect on the sustained current but completely blocked the transient current with an IC50 of 1.8 mM. TEA blocked the sustained current with an IC50 of 7.9 mM without significantly reducing the transient current. Both current components were resistant to dendrotoxin (500 nM).

  • passive propagation of ltd to Stratum Oriens alveus inhibitory neurons modulates the temporoammonic input to the hippocampal ca1 region
    Neuron, 1995
    Co-Authors: Gianmaria Maccaferri, Chris J Mcbain
    Abstract:

    Excitatory synaptic activity in horizontal Stratum Oriens-alveus interneurons (OAIs) is driven by the recurrent collaterals of CA1 pyramidal cells and is strongly influenced by protocols that elicit synaptic plasticity in these principal neurons. Induction of LTD in the Schaffer collateral-CA1 pyramidal neuron synapse causes a passive down-regulation of Stratum radiatum-evoked excitatory synaptic responses onto OAIs. In addition, we show that the strength of the temporoammonic input to the CA1 pyramidal neuron distal dendrites is regulated by OAI activity. The passive propagation of LTD to OAIs consequently disinhibits the direct entorhinal cortex-CA1 input, resulting in an enhanced excitation of CA1 pyramidal neurons by a mechanism not requiring activation of the trisynaptic pathway.

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

  • the hyperpolarization activated current ih and its contribution to pacemaker activity in rat ca1 hippocampal Stratum Oriens alveus interneurones
    The Journal of Physiology, 1996
    Co-Authors: Gianmaria Maccaferri, Chris J Mcbain
    Abstract:

    1. The hyperpolarization-activated current (Ih) and its role in pacemaking activity in rat hippocampal Stratum Oriens-alveus interneurones was studied using whole-cell and perforated patch-clamp configurations. 2. Voltage-clamp recordings revealed Ih as a slowly activating, inward current, activated by hyperpolarizing steps (holding potential, Vh = -40 mV), with a reversal potential close to -30 mV. Its activation curve ranged from approximately -50 to -120 mV with a mid-activation point of -84.1 mV. 3. Ih was blocked by external application of Cs+ (2-5 mM) and ZD7288 (100 microM), but not by Ba2+ (1 mM). 4. Ih was potentiated by both noradrenaline and isoprenaline by a mechanism consistent with a shift in the Ih activation curve. 5. Under current-clamp conditions (Vh = -60 mV), ZD7288 induced a membrane hyperpolarization concomitant with an increase in the membrane input resistance and abolished the voltage sag generated by hyperpolarizing current injection. 6. Analysis of the current-discharge relationship revealed that block of Ih differentially increased the firing frequency of spikes occurring early in the train compared with those occurring late in the discharge. 7. When applied to spontaneously firing cells, ZD7288 reduced the firing frequency by selectively altering the time course of the interspike interval, while minimally affecting other action potential characteristics. Similarly, isoprenaline increased the spontaneous firing frequency by an effect exclusively on the after-hyperpolarization and interspike interval. 8. These results provide evidence for the involvement of Ih in the excitability and generation of spontaneous firing in hippocampal Stratum Oriens-alveus interneurones.

  • passive propagation of ltd to Stratum Oriens alveus inhibitory neurons modulates the temporoammonic input to the hippocampal ca1 region
    Neuron, 1995
    Co-Authors: Gianmaria Maccaferri, Chris J Mcbain
    Abstract:

    Excitatory synaptic activity in horizontal Stratum Oriens-alveus interneurons (OAIs) is driven by the recurrent collaterals of CA1 pyramidal cells and is strongly influenced by protocols that elicit synaptic plasticity in these principal neurons. Induction of LTD in the Schaffer collateral-CA1 pyramidal neuron synapse causes a passive down-regulation of Stratum radiatum-evoked excitatory synaptic responses onto OAIs. In addition, we show that the strength of the temporoammonic input to the CA1 pyramidal neuron distal dendrites is regulated by OAI activity. The passive propagation of LTD to OAIs consequently disinhibits the direct entorhinal cortex-CA1 input, resulting in an enhanced excitation of CA1 pyramidal neurons by a mechanism not requiring activation of the trisynaptic pathway.

Dimitri M Kullmann - One of the best experts on this subject based on the ideXlab platform.

  • t type calcium channels contribute to nmda receptor independent synaptic plasticity in hippocampal regular spiking Oriens alveus interneurons
    The Journal of Physiology, 2017
    Co-Authors: Elizabeth Nicholson, Dimitri M Kullmann
    Abstract:

    Key points Regular-spiking interneurons in the hippocampal Stratum Oriens exhibit a form of long-term potentiation of excitatory transmission that is independent of NMDA receptors but requires co-activation of Ca2+ -permeable AMPA receptors and group I metabotropic glutamate receptors. We show that T-type Ca2+ channels are present in such interneurons. Blockade of T-type currents prevents the induction of long-term potentiation, and also interferes with long-lasting potentiation induced either by postsynaptic trains of action potentials or by pairing postsynaptic hyperpolarization with activation of group I metabotropic receptors. Several Ca2+ sources thus converge on the induction of NMDA receptor independent synaptic plasticity. Abstract NMDA receptor independent long-term potentiation (LTP) in hippocampal Stratum Oriens-alveus (O/A) interneurons requires co-activation of postsynaptic group I metabotropic glutamate receptors (mGluRs) and Ca2+ -permeable AMPA receptors. The rectification properties of such AMPA receptors contribute to the preferential induction of LTP at hyperpolarized potentials. A persistent increase in excitatory transmission can also be triggered by exogenous activation of group I mGluRs at the same time as the interneuron is hyperpolarized, or by postsynaptic trains of action potentials in the absence of presynaptic stimulation. In the present study, we identify low-threshold transient (T-type) channels as a further source of Ca2+ that contributes to synaptic plasticity. T-type Ca2+ currents were detected in mouse regular-spiking O/A interneurons. Blocking T-type currents pharmacologically prevented LTP induced by high-frequency stimulation of glutamatergic axons, or by application of the group I mGluR agonist dihydroxyphenylglycine, paired with postsynaptic hyperpolarization. T-type current blockade also prevented synaptic potentiation induced by postsynaptic action potential trains. Several sources of Ca2+ thus converge on NMDA receptor independent LTP induction in O/A interneurons.

  • induction of anti hebbian ltp in ca1 Stratum Oriens interneurons interactions between group i metabotropic glutamate receptors and m1 muscarinic receptors
    The Journal of Neuroscience, 2015
    Co-Authors: Dimitri M Kullmann, Caroline Le Duigou, Etienne Savary, Richard B Miles
    Abstract:

    An anti-Hebbian form of LTP is observed at excitatory synapses made with some hippocampal interneurons. LTP induction is facilitated when postsynaptic interneurons are hyperpolarized, presumably because Ca2+ entry through Ca2+-permeable glutamate receptors is enhanced. The contribution of modulatory transmitters to anti-Hebbian LTP induction remains to be established. Activation of group I metabotropic receptors (mGluRs) is required for anti-Hebbian LTP induction in interneurons with cell bodies in the CA1 Stratum Oriens. This region receives a strong cholinergic innervation from the septum, and muscarinic acetylcholine receptors (mAChRs) share some signaling pathways and cooperate with mGluRs in the control of neuronal excitability. We therefore examined possible interactions between group I mGluRs and mAChRs in anti-Hebbian LTP at synapses which excite Oriens interneurons in rat brain slices. We found that blockade of either group I mGluRs or M1 mAChRs prevented the induction of anti-Hebbian LTP by pairing presynaptic activity with postsynaptic hyperpolarization. Blocking either receptor also suppressed long-term effects of activation of the other G-protein coupled receptor on interneuron membrane potential. However, no crossed blockade was detected for mGluR or mAchR effects on interneuron after-burst potentials or on the frequency of miniature EPSPs. Paired recordings between pyramidal neurons and Oriens interneurons were obtained to determine whether LTP could be induced without concurrent stimulation of cholinergic axons. Exogenous activation of mAChRs led to LTP, with changes in EPSP amplitude distributions consistent with a presynaptic locus of expression. LTP, however, required noninvasive presynaptic and postsynaptic recordings. SIGNIFICANCE STATEMENT In the hippocampus, a form of NMDA receptor-independent long-term potentiation (LTP) occurs at excitatory synapses made on some inhibitory neurons. This is preferentially induced when postsynaptic interneurons are hyperpolarized, depends on Ca2+ entry through Ca2+-permeable AMPA receptors, and has been labeled anti-Hebbian LTP. Here we show that this form of LTP also depends on activation of both group I mGluR and M1 mAChRs. We demonstrate that these G-protein coupled receptors (GPCRs) interact, because the blockade of one receptor suppresses long-term effects of activation of the other GPCR on both LTP and interneuron membrane potential. This LTP was also detected in paired recordings, although only when both presynaptic and postsynaptic recordings did not perturb the intracellular medium. Changes in EPSP amplitude distributions in dual recordings were consistent with a presynaptic locus of expression.

Christine E Gee - One of the best experts on this subject based on the ideXlab platform.