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Action Potentials

The Experts below are selected from a list of 258 Experts worldwide ranked by ideXlab platform

Bert Sakmann – 1st expert on this subject based on the ideXlab platform

  • backpropagating Action Potentials in neurones measurement mechanisms and potential functions
    Progress in Biophysics & Molecular Biology, 2005
    Co-Authors: Jack Waters, Andreas T Schaefer, Bert Sakmann

    Abstract:

    Here we review some properties and functions of backpropagating Action Potentials in the dendrites of mammalian CNS neurones. We focus on three main aspects: firstly the current techniques available for measuring backpropagating Action Potentials, secondly the morphological parameters and voltage gated ion channels that determine Action potential backpropagation and thirdly the potential functions of backpropagating Action Potentials in real neuronal networks.

  • calcium Action Potentials restricted to distal apical dendrites of rat neocortical pyramidal neurons
    The Journal of Physiology, 1997
    Co-Authors: Jackie Schiller, Greg J Stuart, Yitzhak Schiller, Bert Sakmann

    Abstract:

    1. Simultaneous whole-cell voltage and Ca2+ fluorescence measurements were made from the distal apical dendrites and the soma of thick tufted pyramidal neurons in layer 5 of 4-week-old (P28-32) rat neocortex slices to investigate whether activation of distal synaptic inputs can initiate regenerative responses in dendrites. 2. Dual whole-cell voltage recordings from the distal apical trunk and primary tuft branches (540-940 microns distal to the soma) showed that distal synaptic stimulation (upper layer 2) evoking a subthreshold depolarization at the soma could initiate regenerative Potentials in distal branches of the apical tuft which were either graded or all-or-none. These regenerative Potentials did not propagate actively to the soma and axon. 3. Calcium fluorescence measurements along the apical dendrites indicated that the regenerative Potentials were associated with a transient increase in the concentration of intracellular free calcium ([Ca2+]i) restricted to distal dendrites. 4. Cadmium added to the bath solution blocked both the all-or-more dendritic regenerative Potentials and local dendritic [Ca2+]i transients evoked by distal dendritic current injection. Thus, the regenerative Potentials in distal dendrites represent local Ca2+ Action Potentials. 5. Initiation of distal Ca2+ Action Potentials by a synaptic stimulus required coactivation of AMPA- and NMDA-type glutamate receptor channels. 6. It is concluded that in neocortical layer 5 pyramidal neurons of P28-32 animals glutamatergic synaptic inputs to the distal apical dendrites can be amplified via local Ca2+ Action Potentials which do not reach threshold for axonal AP initiation. As amplification of distal excitatory synaptic input is associated with a localized increase in [Ca2+]i these Ca2+ Action Potentials could control the synaptic efficacy of the distal cortico-cortical inputs to layer 5 pyramidal neurons.

  • active propagation of somatic Action Potentials into neocortical pyramidal cell dendrites
    Nature, 1994
    Co-Authors: Greg J Stuart, Bert Sakmann

    Abstract:

    THE dendrites of neurons in the mammalian central nervous system have been considered as electrically passive structures which funnel synaptic Potentials to the soma and axon initial segment, the site of Action potential initiation1,2. More recent studies, however, have shown that the dendrites of many neurons are not passive, but contain active conductances3,4. The role of these dendritic voltage-activated channels in the initiation of Action Potentials in neurons is largely unknown. To assess this directly, patch-clamp recordings were made from the dendrites of neocortical pyramidal cells in brain slices. Voltage-activated sodium currents were observed in dendritic outside-out patches, while Action Potentials could be evoked by depolarizing current pulses or by synaptic stimulation during dendritic whole-cell recordings. To determine the site of initiation of these Action Potentials, simultaneous whole-cell recordings were made from the soma and the apical dendrite or axon of the same cell. These experiments showed that Action Potentials are initiated first in the axon and then actively propagate back into the dendritic tree.

Greg J Stuart – 2nd expert on this subject based on the ideXlab platform

  • calcium Action Potentials restricted to distal apical dendrites of rat neocortical pyramidal neurons
    The Journal of Physiology, 1997
    Co-Authors: Jackie Schiller, Greg J Stuart, Yitzhak Schiller, Bert Sakmann

    Abstract:

    1. Simultaneous whole-cell voltage and Ca2+ fluorescence measurements were made from the distal apical dendrites and the soma of thick tufted pyramidal neurons in layer 5 of 4-week-old (P28-32) rat neocortex slices to investigate whether activation of distal synaptic inputs can initiate regenerative responses in dendrites. 2. Dual whole-cell voltage recordings from the distal apical trunk and primary tuft branches (540-940 microns distal to the soma) showed that distal synaptic stimulation (upper layer 2) evoking a subthreshold depolarization at the soma could initiate regenerative Potentials in distal branches of the apical tuft which were either graded or all-or-none. These regenerative Potentials did not propagate actively to the soma and axon. 3. Calcium fluorescence measurements along the apical dendrites indicated that the regenerative Potentials were associated with a transient increase in the concentration of intracellular free calcium ([Ca2+]i) restricted to distal dendrites. 4. Cadmium added to the bath solution blocked both the all-or-more dendritic regenerative Potentials and local dendritic [Ca2+]i transients evoked by distal dendritic current injection. Thus, the regenerative Potentials in distal dendrites represent local Ca2+ Action Potentials. 5. Initiation of distal Ca2+ Action Potentials by a synaptic stimulus required coactivation of AMPA- and NMDA-type glutamate receptor channels. 6. It is concluded that in neocortical layer 5 pyramidal neurons of P28-32 animals glutamatergic synaptic inputs to the distal apical dendrites can be amplified via local Ca2+ Action Potentials which do not reach threshold for axonal AP initiation. As amplification of distal excitatory synaptic input is associated with a localized increase in [Ca2+]i these Ca2+ Action Potentials could control the synaptic efficacy of the distal cortico-cortical inputs to layer 5 pyramidal neurons.

  • initiation and spread of sodium Action Potentials in cerebellar purkinje cells
    Neuron, 1994
    Co-Authors: Greg J Stuart, Michael Hausser

    Abstract:

    Simultaneous whole-cell recordings were made from the soma and dendrites of cerebellar Purkinje cells in rat brain slices. Sodium Action Potentials, evoked by either depolarizing current pulses or synaptic stimulation of parallel or climbing fibers, always occurred first at the soma and decreased in amplitude with increasing distance into the dendrites. Simultaneous somatic and axonal recordings showed that these Action Potentials were initiated in the axon. Outside-out patches excised from the soma and dendrites revealed that the sodium channel current density decreased with distance from the soma. Consistent with this finding, comparable attenuation was observed for evoked Action Potentials and simulated Action potential waveforms when sodium channels were blocked. These results show that sodium Action Potentials in cerebellar Purkinje cells are initiated in the axon and then spread passively into the dendritic tree.

  • active propagation of somatic Action Potentials into neocortical pyramidal cell dendrites
    Nature, 1994
    Co-Authors: Greg J Stuart, Bert Sakmann

    Abstract:

    THE dendrites of neurons in the mammalian central nervous system have been considered as electrically passive structures which funnel synaptic Potentials to the soma and axon initial segment, the site of Action potential initiation1,2. More recent studies, however, have shown that the dendrites of many neurons are not passive, but contain active conductances3,4. The role of these dendritic voltage-activated channels in the initiation of Action Potentials in neurons is largely unknown. To assess this directly, patch-clamp recordings were made from the dendrites of neocortical pyramidal cells in brain slices. Voltage-activated sodium currents were observed in dendritic outside-out patches, while Action Potentials could be evoked by depolarizing current pulses or by synaptic stimulation during dendritic whole-cell recordings. To determine the site of initiation of these Action Potentials, simultaneous whole-cell recordings were made from the soma and the apical dendrite or axon of the same cell. These experiments showed that Action Potentials are initiated first in the axon and then actively propagate back into the dendritic tree.

Jose A Garrido – 3rd expert on this subject based on the ideXlab platform

  • Flexible graphene transistors for recording cell Action Potentials
    2D Materials, 2016
    Co-Authors: Benno M. Blaschke, Martin Lottner, Simon Drieschner, Andrea Bonaccini Calia, Karolina Stoiber, Lionel Rousseau, Gaëlle Lissourges, Jose A Garrido

    Abstract:

    Graphene solution-gated field-effect transistors (SGFETs) are a promising platform for the recording of cell Action Potentials due to the intrinsic high signal amplification of graphene transistors. In addition, graphene technology fulfils important key requirements for for in-vivo applications, such as biocompability, mechanical flexibility, as well as ease of high density integration. In this paper we demonstrate the fabrication of flexible arrays of graphene SGFETs on polyimide, a biocompatible polymeric substrate. We investigate the transistor’s transconductance and intrinsic electronic noise which are key parameters for the device sensitivity, confirming that the obtained values are comparable to those of rigid graphene SGFETs. Furthermore, we show that the devices do not degrade during repeated bending and the transconductance, governed by the electronic properties of graphene, is unaffected by bending. After cell culture, we demonstrate the recording of cell Action Potentials from cardiomyocyte-like cells with a high signal-to-noise ratio that is higher or comparable to competing state of the art technologies. Our results highlight the great capabilities of flexible graphene SGFETs in bioelectronics, providing a solid foundation for in-vivo experiments and, eventually, for graphene-based neuroprosthetics.

  • Graphene transistor arrays for recording Action Potentials from electrogenic cells
    Advanced Materials, 2011
    Co-Authors: Lucas H. Hess, Michael Jansen, Vanessa Maybeck, Moritz V. Hauf, Max Seifert, Martin Stutzmann, Ian D. Sharp, Andreas Offenhäusser, Jose A Garrido

    Abstract:

    Arrays of graphene solution-gated field-effect transistors are fabricated for the detection of electrical activity of electrogenic cells. Cardiomyocyte-like cells are cultured on the transistor arrays and their Action Potentials are detected by the underlying transistors. The analysis of the recorded cell signals and the electronic noise of the transistors confirm that graphene transistors surpass state-of-the-art devices for bioelectronic applications. Copyright 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.