Action potential initiation and propagation in a branching dendritic model of a CA3 pyramidal neuron

In this study, the signal transmission and the spiking patterns of a CA3 pyramidal neuron were simulated through a 69-compartment model with branching dendritic structure. For the simulation, we numerically solved coupled first-order nonlinear ordinary differential equations using fourth order Runge-Kutta method with step size of 2.5×10-3ms. By introducing steady current into the soma, action potentials (APs) were induced. Results reveal two main firing properties of CA3 pyramidal neuron under constant stimulation current: spike frequency adaptation and intrinsic bursting. Results also show AP is initiated in the axon-initial segment 12.5µm - 87.75µm from the center of the soma and propagated retrogradely (backpropagation) into the dendrites. APs propagated in the axon displayed no attenuation while APs backpropagated in dendrites demonstrated decrease in amplitude and increase in spike duration. The calculated backpropagation ratio, (15.6±0.18) × 10-2, suggests that backpropagating APs underwent significant attenuation.