Presynaptic action potential amplification by voltage-gated Na+ channels in hippocampal mossy fiber boutons

Neuron. 2005 Feb 3;45(3):405-17. doi: 10.1016/j.neuron.2004.12.048.


Action potentials in central neurons are initiated near the axon initial segment, propagate into the axon, and finally invade the presynaptic terminals, where they trigger transmitter release. Voltage-gated Na(+) channels are key determinants of excitability, but Na(+) channel density and properties in axons and presynaptic terminals of cortical neurons have not been examined yet. In hippocampal mossy fiber boutons, which emerge from parent axons en passant, Na(+) channels are very abundant, with an estimated number of approximately 2000 channels per bouton. Presynaptic Na(+) channels show faster inactivation kinetics than somatic channels, suggesting differences between subcellular compartments of the same cell. Computational analysis of action potential propagation in axon-multibouton structures reveals that Na(+) channels in boutons preferentially amplify the presynaptic action potential and enhance Ca(2+) inflow, whereas Na(+) channels in axons control the reliability and speed of propagation. Thus, presynaptic and axonal Na(+) channels contribute differentially to mossy fiber synaptic transmission.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Action Potentials / physiology*
  • Animals
  • Calcium / metabolism
  • Calcium Signaling / physiology
  • Cell Compartmentation / physiology
  • Ion Channel Gating / physiology
  • Mossy Fibers, Hippocampal / physiology*
  • Organ Culture Techniques
  • Presynaptic Terminals / physiology*
  • Rats
  • Rats, Wistar
  • Sodium Channels / physiology*
  • Synaptic Membranes / physiology
  • Synaptic Transmission / physiology*


  • Sodium Channels
  • Calcium