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Nat Neurosci. 2010 Jul;13(7):852-60. doi: 10.1038/nn.2574. Epub 2010 Jun 13.

Na+ imaging reveals little difference in action potential-evoked Na+ influx between axon and soma.

Author information

1
Department of Physiology, Faculty of Health Sciences, Ben-Gurion University of the Negev, Beer Sheva, Israel. ilya@bgu.ac.il

Abstract

In cortical pyramidal neurons, the axon initial segment (AIS) is pivotal in synaptic integration. It has been asserted that this is because there is a high density of Na(+) channels in the AIS. However, we found that action potential-associated Na(+) flux, as measured by high-speed fluorescence Na(+) imaging, was about threefold larger in the rat AIS than in the soma. Spike-evoked Na(+) flux in the AIS and the first node of Ranvier was similar and was eightfold lower in basal dendrites. At near-threshold voltages, persistent Na(+) conductance was almost entirely axonal. On a time scale of seconds, passive diffusion, and not pumping, was responsible for maintaining transmembrane Na(+) gradients in thin axons during high-frequency action potential firing. In computer simulations, these data were consistent with the known features of action potential generation in these neurons.

PMID:
20543843
PMCID:
PMC3102307
DOI:
10.1038/nn.2574
[Indexed for MEDLINE]
Free PMC Article

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