"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. ... In computer simulations, these data were consistent with the known features of action potential generation in these neurons."
Model Type: Neuron or other electrically excitable cell
Region(s) or Organism(s): Neocortex
Cell Type(s): Neocortex U1 L5B pyramidal pyramidal tract GLU cell; Neocortex L5/6 pyramidal GLU cell
Currents: I Sodium; I Na,p; I Potassium
Model Concept(s): Action Potentials; Active Dendrites; Reaction-diffusion
Simulation Environment: NEURON; Python
Implementer(s): McDougal, Robert [robert.mcdougal at yale.edu]
References:
Fleidervish IA, Lasser-Ross N, Gutnick MJ, Ross WN. (2010). Na+ imaging reveals little difference in action potential-evoked Na+ influx between axon and soma. Nature neuroscience. 13 [PubMed]