On the mechanisms underlying the depolarization block in the spiking dynamics of CA1 pyramidal neurons
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Under sustained input current of increasing strength neurons eventually stop firing, entering a depolarization block. This is a robust effect that is not usually explored in experiments or explicitly implemented or tested in models. However, the range of current strength needed for a depolarization block could be easily reached with a random background activity of only a few hundred excitatory synapses. Depolarization block may thus be an important property of neurons that should be better characterized in experiments and explicitly taken into account in models at all implementation scales. Here we analyze the spiking dynamics of CA1 pyramidal neuron models using the same set of ionic currents on both an accurate morphological reconstruction and on its reduction to a single-compartment. The results show the specific ion channel properties and kinetics that are needed to reproduce the experimental findings, and how their interplay can drastically modulate the neuronal dynamics and the input current range leading to a depolarization block. We suggest that this can be one of the rate-limiting mechanisms protecting a CA1 neuron from excessive spiking activity.
KeywordsDepolarization block CA1 pyramidal neuron Bifurcation analysis Kinetics
Financial support from “Compagnia di San Paolo” is gratefully acknowledged. We thank Drs. S. Cuomo and P. De Michele (Department of Mathematics and Applications “Renato Caccioppoli”, University of Naples Federico II) for assistance in running the parallel version of our morphological model and for the use of the S.Co.P.E. Grid infrastructure of University of Naples Federico II.
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