Spatial mismatch between the Na+ flux and spike initiation in axon initial segment.

ABSTRACT: It is widely believed that, in cortical pyramidal cells, action potentials (APs) initiate in the distal portion of axon initial segment (AIS) because that is where Na(+) channel density is highest. To investigate the relationship between the density of Na(+) channels and the spatiotemporal pattern of AP initiation, we simultaneously recorded Na(+) flux and action currents along the proximal axonal length. We found that functional Na(+) channel density is approximately four times lower in the AP trigger zone than in the middle of the AIS, where it is highest. Computational analysis of AP initiation revealed a paradoxical mismatch between the AP threshold and Na(+) channel density, which could be explained by the lopsided capacitive load imposed on the proximal end of the AIS by the somatode

SUBMITTER: Baranauskas G 

PROVIDER: S-EPMC3593864 | biostudies-literature | 2013 Mar

REPOSITORIES: biostudies-literature