Temporal integration can readily switch between sublinear and supralinear summation.
Temporal summation at dendrites of cultured rat hippocampal neurons was examined as a function of the interval separating two dendritic inputs. A novel method that relies on single-mode optical fibers to achieve rapid photorelease of glutamate was developed. Dendritic excitation achieved with this approach resembles that associated with miniature excitatory postsynaptic currents (mEPSCs), but the strengths, sites, and timing of the inputs can be precisely controlled. Dendritic summation deviated markedly from behavior predicted by passive cable theory. Subthreshold temporal summation varied as a triphasic function of the interpulse interval. As the interpulse interval decreased, local dendritic Na+ conductances were recruited to generate a marked transition from sublinear to supralinear summation. These results suggest that active dendritic conductances acting in concert with passive cable properties may serve to boost coincident synaptic inputs and attenuate noncoincident inputs.
Margulis
M
M
Department of Neurology, University of Maryland School of Medicine Baltimore, Maryland 21201, USA.
Tang
C M
CM
D000818:Animals; D002478:Cells, Cultured; D003712:Dendrites / Q000378:metabolism* / Q000528:radiation effects; D019706:Excitatory Postsynaptic Potentials / Q000502:physiology*; D005336:Fiber Optic Technology; D005971:Glutamates / Q000528:radiation effects*; D018698:Glutamic Acid / Q000378:metabolism*; D006624:Hippocampus / Q000166:cytology / Q000502:physiology*; D015640:Ion Channel Gating / Q000502:physiology; D007834:Lasers; D008433:Mathematics; D008959:Models, Neurological; D055100:Optical Fibers; D018408:Patch-Clamp Techniques; D010775:Photic Stimulation / Q000295:instrumentation; D010777:Photochemistry / Q000295:instrumentation; D015221:Potassium Channels / Q000502:physiology; D051381:Rats; D026941:Sodium Channel Blockers; D015222:Sodium Channels / Q000502:physiology; D009435:Synaptic Transmission / Q000502:physiology*; D013779:Tetrodotoxin / Q000494:pharmacology; D013997:Time Factors; D014466:Ultraviolet Rays
C102508:(carboxy-2-nitrobenzyl)glutamic acid; D005971:Glutamates; D015221:Potassium Channels; D026941:Sodium Channel Blockers; D015222:Sodium Channels; D018698:Glutamic Acid; D013779:Tetrodotoxin