Ca2+ accumulations in dendrites of neocortical pyramidal neurons: an apical band and evidence for two functional compartments.
Apical dendrites constitute a prominent feature of the microcircuitry in the neocortex, yet their function is poorly understood. Using fura-2 imaging of layer 5 pyramidal neurons from slices of rat somatosensory cortex, we have investigated the Ca2+ influx into dendrites under intracellular, antidromic, synaptic, and receptor-agonist stimulation. We find three spatial patterns of Ca2+ accumulations: an apical band in the apical dendrite approximately 500 microns from the soma, an accumulation restricted to the basal dendrites, soma, and proximal apical dendrite, and a combination of both of these. We show that the apical band can be activated antidromically and synaptically and that, under blocked Na+ and K+ conductances, it generates Ca2+ spikes. Thus, the apical band may serve as a dendritic trigger zone for regenerative Ca2+ spikes or as a current amplifier for distal synaptic events. Our results suggest that the distal apical dendrite should be considered a separate functional compartment from the rest of the cell.
Yuste
R
R
Biological Computation Research Department, AT&T Bell Laboratories, Murray Hill, New Jersey 07974.
Gutnick
M J
MJ
Saar
D
D
Delaney
K R
KR
Tank
D W
DW
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002540:Cerebral Cortex / Q000187:drug effects / Q000648:ultrastructure*; D003712:Dendrites / Q000187:drug effects / Q000502:physiology*; D004553:Electric Conductivity; D004594:Electrophysiology; D005071:Evoked Potentials; D005456:Fluorescent Dyes; D016257:Fura-2; D016202:N-Methylaspartate / Q000494:pharmacology; D009474:Neurons / Q000648:ultrastructure*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012964:Sodium / Q000378:metabolism; D013569:Synapses / Q000502:physiology; D019789:Tetraethylammonium; D013757:Tetraethylammonium Compounds / Q000494:pharmacology; D013779:Tetrodotoxin / Q000494:pharmacology
D005456:Fluorescent Dyes; D013757:Tetraethylammonium Compounds; D013779:Tetrodotoxin; D016202:N-Methylaspartate; D019789:Tetraethylammonium; D012964:Sodium; D002118:Calcium; D016257:Fura-2