Activation of NMDA receptors in rat dentate gyrus granule cells by spontaneous and evoked transmitter release.

Activation of N-methyl-D-aspartate (NMDA) receptors by synaptically released glutamate in the nervous system is usually studied using evoked events mediated by a complex mixture of AMPA, kainate, and NMDA receptors. Here we have characterized pharmacologically isolated spontaneous NMDA receptor-mediated synaptic events and compared them to stimulus evoked excitatory postsynaptic currents (EPSCs) in the same cell to distinguish between various modes of activation of NMDA receptors. Spontaneous NMDA receptor-mediated EPSCs recorded at 34 degrees C in dentate gyrus granule cells (DGGC) have a frequency of 2.5 +/- 0.3 Hz and an average peak amplitude of 13.2 +/- 0.8 pA, a 10-90% rise time of 5.4 +/- 0.3 ms, and a decay time constant of 42.1 +/- 2.1 ms. The single-channel conductance estimated by nonstationary fluctuation analysis was 60 +/- 5 pS. The amplitudes (46.5 +/- 6.4 pA) and 10-90% rise times (18 +/- 2.3 ms) of EPSCs evoked from the entorhinal cortex/subiculum border are significantly larger than the same parameters for spontaneous events (paired t-test, P < 0.05, n = 17). Perfusion of 50 microM D(-)-2-amino-5-phosphonopentanoic acid blocked all spontaneous activity and caused a significant baseline current shift of 18.8 +/- 3.0 pA, thus identifying a tonic conductance mediated by NMDA receptors. The NR2B antagonist ifenprodil (10 microM) significantly reduced the frequency of spontaneous events but had no effect on their kinetics or on the baseline current or variance. At the same time, the peak current and charge of stimulus-evoked events were significantly diminished by ifenprodil. Thus spontaneous NMDA receptor-mediated events in DGGC are predominantly mediated by NR2A or possibly NR2A/NR2B receptors while the activation of NR2B receptors reduces the excitability of entorhinal afferents either directly or through an effect on the entorhinal cells.

[1]  B. Clark,et al.  A Direct Comparison of the Single-Channel Properties of Synaptic and Extrasynaptic NMDA Receptors , 1997, The Journal of Neuroscience.

[2]  C. Drake,et al.  Ultrastructural evidence for presynaptic μ opioid receptor modulation of synaptic plasticity in NMDA-receptor-containing dendrites in the dentate gyrus , 2001, Brain Research Bulletin.

[3]  F. Sigworth.  The variance of sodium current fluctuations at the node of Ranvier , 1980, The Journal of physiology.

[4]  G. Rumbaugh,et al.  Distinct Synaptic and Extrasynaptic NMDA Receptors in Developing Cerebellar Granule Neurons , 1999, The Journal of Neuroscience.

[5]  R. Nicoll,et al.  Analysis of excitatory synaptic action in pyramidal cells using whole‐cell recording from rat hippocampal slices. , 1990, The Journal of physiology.

[6]  G. Westbrook,et al.  Channel kinetics determine the time course of NMDA receptor-mediated synaptic currents , 1990, Nature.

[7]  S. Vicini,et al.  Regional and Ontogenic Expression of the NMDA Receptor Subunit NR2D Protein in Rat Brain Using a Subunit‐Specific Antibody , 1996, Journal of neurochemistry.

[8]  Y. Smith,et al.  Presynaptic NMDA receptor subunit immunoreactivity in GABAergic terminals in rat brain , 2000, The Journal of comparative neurology.

[9]  A. Gibb,et al.  Subtypes of NMDA receptors in new‐born rat hippocampal granule cells , 2002, The Journal of physiology.

[10]  G. Westbrook,et al.  The Incorporation of NMDA Receptors with a Distinct Subunit Composition at Nascent Hippocampal Synapses In Vitro , 1999, The Journal of Neuroscience.

[11]  L. Raymond,et al.  Changes in agonist concentration dependence that are a function of duration of exposure suggest N-methyl-D-aspartate receptor nonsaturation during synaptic stimulation. , 2001, Molecular pharmacology.

[12]  E. Aizenman,et al.  Functional consequences of NR2 subunit composition in single recombinant N-methyl-D-aspartate receptors. , 1997, Proceedings of the National Academy of Sciences of the United States of America.

[13]  S. Vicini,et al.  Functional and pharmacological differences between recombinant N-methyl-D-aspartate receptors. , 1998, Journal of neurophysiology.

[14]  I. Módy,et al.  Noise analysis of miniature IPSCs in adult rat brain slices: properties and modulation of synaptic GABAA receptor channels. , 1994, Journal of neurophysiology.

[15]  D. Kullmann,et al.  Extracellular glutamate diffusion determines the occupancy of glutamate receptors at CA1 synapses in the hippocampus. , 1999, Philosophical transactions of the Royal Society of London. Series B, Biological sciences.

[16]  J. Macdonald,et al.  Distinct Roles of Synaptic and Extrasynaptic NMDA Receptors in Excitotoxicity , 2000, The Journal of Neuroscience.

[17]  R. S. Jones,et al.  NR2B-containing NMDA autoreceptors at synapses on entorhinal cortical neurons. , 2001, Journal of neurophysiology.

[18]  N. Lozovaya,et al.  Enhancement of glutamate release uncovers spillover-mediated transmission by N-methyl-d-aspartate receptors in the rat hippocampus , 1999, Neuroscience.

[19]  A. Wenzel,et al.  Distribution of NMDA receptor subunit proteins NR2A, 2B, 2C and 2D in rat brain , 1995, Neuroreport.

[20]  Bert Sakmann,et al.  Heteromeric NMDA Receptors: Molecular and Functional Distinction of Subtypes , 1992, Science.

[21]  Petter Laake,et al.  Different modes of expression of AMPA and NMDA receptors in hippocampal synapses , 1999, Nature Neuroscience.

[22]  K Williams,et al.  Ifenprodil discriminates subtypes of the N-methyl-D-aspartate receptor: selectivity and mechanisms at recombinant heteromeric receptors. , 1993, Molecular pharmacology.

[23]  R. Silver,et al.  Estimated conductance of glutamate receptor channels activated during EPSCs at the cerebellar mossy fiber-granule cell synapse , 1993, Neuron.

[24]  F. D. da Silva,et al.  A presynaptic N‐methyl‐d‐aspartate autoreceptor in rat hippocampus modulating amino acid release from a cytoplasmic pool , 1998, The European journal of neuroscience.

[25]  M. Häusser,et al.  Estimating the Time Course of the Excitatory Synaptic Conductance in Neocortical Pyramidal Cells Using a Novel Voltage Jump Method , 1997, The Journal of Neuroscience.

[26]  Masahiko Watanabe,et al.  Distinct distributions of five N‐methyl‐D‐aspartate receptor channel subunit mRNAs in the forebrain , 1993, The Journal of comparative neurology.

[27]  P. Somogyi,et al.  NMDA Receptor Content of Synapses in Stratum Radiatum of the Hippocampal CA1 Area , 2000, The Journal of Neuroscience.

[28]  G. Rondouin,et al.  Hippocampal kindling in the rat: Intrastructural differences , 1984, Journal of neuroscience research.

[29]  K J Staley,et al.  Integrity of perforant path fibers and the frequency of action potential independent excitatory and inhibitory synaptic events in dentate gyrus granule cells , 1991, Synapse.

[30]  L. Raymond,et al.  Differential sensitivity of recombinant N-methyl-D-aspartate receptor subtypes to zinc inhibition. , 1997, Molecular pharmacology.

[31]  M. Häusser,et al.  Intersynaptic diffusion of neurotransmitter. , 1997, Trends in neurosciences.

[32]  P. Stern,et al.  Single channel properties of cloned NMDA receptors in a human cell line: comparison with results from Xenopus oocytes. , 1994, The Journal of physiology.

[33]  O. Ottersen,et al.  The Arrangement of Glutamate Receptors in Excitatory Synapses , 1999, Annals of the New York Academy of Sciences.

[34]  J. Gilmore,et al.  The effects of ifenprodil and eliprodil on voltage-dependent Ca2+ channels and in gerbil global cerebral ischaemia. , 1996, European journal of pharmacology.

[35]  D. Colquhoun,et al.  Single channel analysis of a novel NMDA channel from Xenopus oocytes expressing recombinant NR1a, NR2A and NR2D subunits. , 2000, The Journal of physiology.

[36]  I. Módy,et al.  Altered effects of ethanol in NR2A(DeltaC/DeltaC) mice expressing C-terminally truncated NR2A subunit of NMDA receptor. , 2001, Neuroscience.

[37]  J. Diamond,et al.  Synaptically Released Glutamate Activates Extrasynaptic NMDA Receptors on Cells in the Ganglion Cell Layer of Rat Retina , 2002, The Journal of Neuroscience.

[38]  G. Westbrook,et al.  Calcineurin acts via the C-terminus of NR2A to modulate desensitization of NMDA receptors , 2002, Neuropharmacology.

[39]  D Colquhoun,et al.  Activation of N‐methyl‐D‐aspartate receptors by L‐glutamate in cells dissociated from adult rat hippocampus. , 1992, The Journal of physiology.

[40]  Robert A. Pearce,et al.  Physiological evidence for two distinct GABAA responses in rat hippocampus , 1993, Neuron.

[41]  A. Wenzel,et al.  Synapse‐specific localization of NMDA and GABAA receptor subunits revealed by antigen‐retrieval immunohistochemistry , 1998, The Journal of comparative neurology.

[42]  J. Isaacson.  Glutamate Spillover Mediates Excitatory Transmission in the Rat Olfactory Bulb , 1999, Neuron.

[43]  A. Momiyama,et al.  Distinct synaptic and extrasynaptic NMDA receptors identified in dorsal horn neurones of the adult rat spinal cord , 2000, The Journal of physiology.

[44]  H. Betz,et al.  Evidence for a Tetrameric Structure of Recombinant NMDA Receptors , 1998, The Journal of Neuroscience.

[45]  G. Paxinos,et al.  The Rat Brain in Stereotaxic Coordinates , 1983 .

[46]  N. Sucher,et al.  An NMDA Receptor Signaling Complex with Protein Phosphatase 2A , 2001, The Journal of Neuroscience.

[47]  Stuart G. Cull-Candy,et al.  NMDA receptor diversity in the cerebellum: identification of subunits contributing to functional receptors , 1998, Neuropharmacology.

[48]  H. Bading,et al.  Extrasynaptic NMDARs oppose synaptic NMDARs by triggering CREB shut-off and cell death pathways , 2002, Nature Neuroscience.

[49]  I. Módy,et al.  Altered effects of ethanol in NR2AΔC/ΔC mice expressing C-terminally truncated NR2A subunit of NMDA receptor , 2001, Neuroscience.

[50]  J. Diamond.  Neuronal Glutamate Transporters Limit Activation of NMDA Receptors by Neurotransmitter Spillover on CA1 Pyramidal Cells , 2001, The Journal of Neuroscience.

[51]  B. Clark,et al.  Activity-Dependent Recruitment of Extrasynaptic NMDA Receptor Activation at an AMPA Receptor-Only Synapse , 2002, The Journal of Neuroscience.

[52]  I. Módy,et al.  Regulation of NMDA channel function by endogenous Ca2+-dependent phosphatase , 1994, Nature.

[53]  D. Colquhoun,et al.  Single‐channel activations and concentration jumps: comparison of recombinant NR1a/NR2A and NR1a/NR2D NMDA receptors , 1998, The Journal of physiology.