Neuron
Volume 11, Issue 2, August 1993, Pages 279-289
Journal home page for Neuron

Article
Estimated conductance of glutamate receptor channels activated during EPSCs at the cerebellar mossy fiber-granule cell synapse

https://doi.org/10.1016/0896-6273(93)90184-SGet rights and content

Abstract

We have analyzed the variance associated with the decay of the non-NMDA receptor component of synaptic currents, recorded from mossy fiber-granule cell synapses in cerebellar slices, to obtain a conductance estimate for the synaptic channel. Current fluctuations arising from the random channel gating properties were separated from those arising from the fluctuations in the population of channels by subtracting the mean excitatory postsynaptic current (EPSC) waveform scaled to the EPSC peak amplitude. A weighted mean single-channel conductance of approximately 20 pS was determined from the relationship between the mean current and the variance around the mean during the decay of evoked and spontaneous synaptic currents. This result suggests that high conductance non-NMDA channels, such as the 10–30 pS glutamate receptor channel previously characterized in granule cells, carry the majority of the fast component of the EPSC at this synapse. In addition, our data are consistent with the activation of surprisingly few (approximately 10) non-NMDA channels by a single packet of transmitter.

References (45)

  • J.M. Bekkers et al.

    NMDA and non-NMDA receptors are co-localized at individual excitatory synapses in cultured rat hippocampus

    Nature

    (1989)
  • D. Colquhoun et al.

    Action of brief pulses of glutamate on AMPA/kainate receptors in patches from different neurones of rat hippocampal slices

    J. Physiol.

    (1992)
  • S.G. Cull-Candy et al.

    Properties of miniature excitatory junctional currents at the locust nerve-muscle junction

    J. Physiol.

    (1982)
  • S.G. Cull-Candy et al.

    Multiple-conductance channels activated by excitatory amino acids in cerebellar neurons

    Nature

    (1987)
  • S.G. Cull-Candy et al.

    On the multiple-conductance single channels activated by excitatory amino acids in large cerebellar neurones of the rat

    J. Physiol.

    (1989)
  • S.G. Cull-Candy et al.

    Noise and single channels activated by excitatory amino acids in rat cerebellar granule neurons

    J. Physiol.

    (1988)
  • S.G. Cull-Candy et al.

    Excitatory amino acid-gated channel types in mammalian neurons and glia

  • R. Dingledine et al.

    Amino acid receptors and uptake systems in the mammalian central nervous system

    CRC Crit. Rev. Neurobiol.

    (1988)
  • F.A. Edwards et al.

    A thin slice preparation for patch clamp recordings from neurones of the mammalian central nervous system

    Pflügers Arch.

    (1989)
  • F.A. Edwards et al.

    Quantal analysis of inhibitory synaptic transmission in the dentate gyrus of rat hippocampal slices: a patch-clamp study

    J. Physiol.

    (1990)
  • G.P. Gasic et al.

    Molecular neurobiology of glutamate receptors

    Annu. Rev. Physiol.

    (1992)
  • M.R. Gold et al.

    Characteristics of inhibitory post-synaptic currents in brain-stem neurones of the lamprey

    J. Physiol.

    (1983)
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