Action potential propagation into the presynaptic dendrites of rat mitral cells.
1. Dendritic patch-clamp recordings were obtained from mitral cells in rat olfactory bulb slices, up to 350 microns from the soma. Simultaneous dendritic and somatic whole-cell recordings indicated that action potentials (APs) evoked by somatic or dendritic current injection were initiated near the soma. Both the large amplitude (100.7 +/- 1.1 mV) and the short duration (1.38 +/- 0.07 ms) of the AP were maintained as the AP propagated back into the primary mitral cell dendrites. 2. Outside-out patches isolated from mitral cell dendrites contained voltage-gated Na+ channels (peak conductance density, 90 pS micron-2 at -10 mV). When an AP was used as a somatic voltage-clamp command in the presence of 1 microM tetrodotoxin (TTX), the amplitude of the dendritic potential was attenuated to 48 +/- 14 mV. This shows that dendritic Na+ channels support the active back-propagation of APs. 3. Dendritic patches contained voltage-gated K+ channels with high density (conductance density, 513 pS micron-2 at 30 mV). Dendritic K+ currents were reduced to 35% by 1 mM external tetraethylammonium chloride (TEACl). When an AP was used as a somatic voltage-clamp command in the presence of TEACl, the dendritic potential was markedly prolonged. This indicates that dendritic K+ channels mediate the fast repolarization of dendritic APs. 4. We conclude that voltage-gated Na+ and K+ channels support dendritic APs with large amplitudes and short durations that may trigger fast transmitter release at dendrodendritic synapses in the olfactory bulb.
Bischofberger
J
J
Physiologisches Institut, Universität Freiburg, Germany.
Jonas
P
P
D000200:Action Potentials; D000818:Animals; D003712:Dendrites / Q000502:physiology*; D004558:Electric Stimulation; D066298:In Vitro Techniques; D015640:Ion Channel Gating / Q000502:physiology; D008856:Microscopy, Fluorescence; D009830:Olfactory Bulb / Q000166:cytology / Q000502:physiology*; D018408:Patch-Clamp Techniques; D015221:Potassium Channels / Q000502:physiology; D017729:Presynaptic Terminals / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D015222:Sodium Channels / Q000502:physiology; D009435:Synaptic Transmission / Q000502:physiology; D019789:Tetraethylammonium / Q000494:pharmacology; D013779:Tetrodotoxin / Q000494:pharmacology
D015221:Potassium Channels; D015222:Sodium Channels; D013779:Tetrodotoxin; D019789:Tetraethylammonium