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

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.

SUBMITTER: Fleidervish IA

PROVIDER: S-EPMC3102307 | biostudies-literature | 2010 Jul

REPOSITORIES: biostudies-literature

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

Fleidervish Ilya A IA Lasser-Ross Nechama N Gutnick Michael J MJ Ross William N WN

Nature neuroscience 20100613 7

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- ...[more]

PMID: 20543843

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

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

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