NMDA receptor-mediated Na+ signals in spines and dendrites.
Spines and dendrites of central neurons represent an important site of synaptic signaling and integration. Here we identify a new, synaptically mediated spine signal with unique properties. Using two-photon Na(+) imaging, we show that suprathreshold synaptic stimulation leads to transient increases in Na(+) concentration in postsynaptic spines and their adjacent dendrites. This local signal is restricted to a dendritic domain near the site of synaptic input. In presumed active spines within this domain, the Na(+) level increases by 30-40 mm even during short bursts of synaptic stimulation. During a long-term potentiation induction protocol (100 Hz, 1 sec), the Na(+) level in the active spines reaches peak amplitudes of approximately 100 mm. We find that the Na(+) transients are mainly mediated by Na(+) entry through NMDA receptor channels and are detected during the coincident occurrence of synaptic potentials and backpropagating action potentials. The large amplitudes of the Na(+) transients and their location on dendritic spines suggest that this signal is an important determinant of electrical and biochemical spine characteristics.
Rose
C R
CR
Institut für Physiologie, Ludwig-Maximilians-Universität München, D-80802 München, Germany. rose@lrz.uni-muenchen.de
Konnerth
A
A
D000200:Action Potentials / Q000502:physiology; D000818:Animals; D022081:Cell Surface Extensions / Q000378:metabolism*; D003712:Dendrites / Q000378:metabolism; D004558:Electric Stimulation / Q000379:methods; D006624:Hippocampus / Q000166:cytology / Q000378:metabolism; D066298:In Vitro Techniques; D017774:Long-Term Potentiation / Q000502:physiology; D008564:Membrane Potentials / Q000502:physiology; D051379:Mice; D018613:Microscopy, Confocal; D018408:Patch-Clamp Techniques; D017966:Pyramidal Cells / Q000378:metabolism*; D016194:Receptors, N-Methyl-D-Aspartate / Q000378:metabolism*; D012684:Sensory Thresholds / Q000502:physiology; D015398:Signal Transduction / Q000502:physiology*; D012964:Sodium / Q000378:metabolism*; D009435:Synaptic Transmission / Q000502:physiology
D016194:Receptors, N-Methyl-D-Aspartate; D012964:Sodium