Citations : Persistent Sodium Current in Layer 5 Neocortical Neurons Is Primarily Generated in the Proximal Axon

Dated: Mar 29, 2006

Publication Name: Journal of Neuroscience

In addition to the well described fast-inactivating component of the Na+ current [transient Na+ current (INaT)], neocortical neurons also exhibit a low-voltage-activated, slowly inactivating “persistent” Na+ current (INaP), which plays a role in determining neuronal excitability and synaptic integration. We investigated the Na+ channels responsible for INaP in layer 5 pyramidal cells using cell-attached and whole-cell recordings in neocortical slices. In simultaneous cell-attached and whole-cell somatic recordings, no persistent Na+ channel activity was detected at potentials at which whole-cell INaP operates. Detailed kinetic analysis of late Na+ channel activity in cell-attached patches at 36°C revealed that somatic Na+ channels do not demonstrate “modal gating” behavior and that the probability of single late openings is extremely low (<1.4 × 10−4 or <0.02% of maximal open probability of INaT). Ensemble averages of these currents did not reveal a sustained component whose amplitude and voltage dependence could account for INaP as seen in whole-cell recordings.

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Contributors: Nadav Astman, Michael J. Gutnick and Ilya A. Fleidervish