title: Presynaptic action potential amplification by voltage-gated Na+ channels in hippocampal mossy fiber boutons.
abstract: 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.
authors.affiliation: Physiologisches Institut der Universität Freiburg, Hermann-Herder-Strasse 7, D-79104 Freiburg, Germany.
authors.forename: Dominique
authors.initials: D
authors.lastname: Engel
authors.forename: Peter
authors.initials: P
authors.lastname: Jonas
mesh_terms: D000200:Action Potentials / Q000502:physiology*; D000818:Animals; D002118:Calcium / Q000378:metabolism; D020013:Calcium Signaling / Q000502:physiology; D002451:Cell Compartmentation / Q000502:physiology; D015640:Ion Channel Gating / Q000502:physiology; D019599:Mossy Fibers, Hippocampal / Q000502:physiology*; D009924:Organ Culture Techniques; D017729:Presynaptic Terminals / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D015222:Sodium Channels / Q000502:physiology*; D013570:Synaptic Membranes / Q000502:physiology; D009435:Synaptic Transmission / Q000502:physiology*
chemical_list: D015222:Sodium Channels; D002118:Calcium