Differential mechanisms of transmission at three types of mossy fiber synapse

J Neurosci. 2000 Nov 15;20(22):8279-89. doi: 10.1523/JNEUROSCI.20-22-08279.2000.


The axons of the dentate gyrus granule cells, the so-called mossy fibers, innervate their inhibitory interneuron and pyramidal neuron targets via both anatomically and functionally specialized synapses. Mossy fiber synapses onto inhibitory interneurons were comprised of either calcium-permeable (CP) or calcium-impermeable (CI) AMPA receptors, whereas only calcium-impermeable AMPA receptors existed at CA3 principal neuron synapses. In response to brief trains of high-frequency stimuli (20 Hz), pyramidal neuron synapses invariably demonstrated short-term facilitation, whereas interneuron EPSCs demonstrated either short-term facilitation or depression. Facilitation at all CI AMPA synapses was voltage independent, whereas EPSCs at CP AMPA synapses showed greater facilitation at -20 than at -80 mV, consistent with a role for the postsynaptic unblock of polyamines. At pyramidal cell synapses, mossy fiber EPSCs possessed marked frequency-dependent facilitation (commencing at stimulation frequencies >0.1 Hz), whereas EPSCs at either type of interneuron synapse showed only moderate frequency-dependent facilitation or underwent depression. Presynaptic metabotropic glutamate receptors (mGluRs) decreased transmission at all three synapse types in a frequency-dependent manner. However, after block of presynaptic mGluRs, transmission at interneuron synapses still did not match the dynamic range of EPSCs at pyramidal neuron synapses. High-frequency stimulation of mossy fibers induced long-term potentiation (LTP), long-term depression (LTD), or no change at pyramidal neuron synapses, interneuron CP AMPA synapses, and CI AMPA synapses, respectively. Induction of LTP or LTD altered the short-term plasticity of transmission onto both pyramidal cells and interneuron CP AMPA synapses by a mechanism consistent with changes in release probability. These data reveal differential mechanisms of transmission at three classes of mossy fiber synapse made onto distinct targets.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Biogenic Polyamines / metabolism
  • Biogenic Polyamines / pharmacology
  • Calcium / metabolism
  • Cell Membrane Permeability / physiology
  • Dentate Gyrus / cytology
  • Dentate Gyrus / metabolism
  • Electric Stimulation
  • Excitatory Postsynaptic Potentials / physiology
  • Hippocampus / cytology
  • Hippocampus / metabolism
  • In Vitro Techniques
  • Interneurons / cytology
  • Interneurons / metabolism
  • Long-Term Potentiation / physiology
  • Mossy Fibers, Hippocampal / metabolism*
  • Neuronal Plasticity / physiology
  • Neurotransmitter Agents / metabolism
  • Nicotinic Antagonists / pharmacology
  • Pyramidal Cells / cytology
  • Pyramidal Cells / metabolism
  • Rats
  • Rats, Sprague-Dawley
  • Reaction Time / physiology
  • Receptors, AMPA / metabolism
  • Receptors, Metabotropic Glutamate / antagonists & inhibitors
  • Receptors, Metabotropic Glutamate / metabolism
  • Receptors, Presynaptic / metabolism
  • Synapses / classification
  • Synapses / metabolism*
  • Synaptic Transmission / drug effects
  • Synaptic Transmission / physiology*


  • Biogenic Polyamines
  • Neurotransmitter Agents
  • Nicotinic Antagonists
  • Receptors, AMPA
  • Receptors, Metabotropic Glutamate
  • Receptors, Presynaptic
  • Calcium