Mechanisms Involved in Spike Frequency Adaptation of a Type S Motoneuron: a Computational Study

A computational model was developed to evaluate the influence of the calcium-dependent potassium conductance (gKCa), the calcium concentration in soma (varying the velocity of calcium extrusion velext and the calcium conductances in soma – gCaN and gCaP), the inclusion of a slow inactivation state variable in soma's fast sodium conductance and the conductance of the persistent sodium current in the initial segment (gNapSI) in the spike-frequency adaptation of a type S motoneuron. Blocking gKCa in the model eliminated the initial phase of the spike frequency adaptation and so, this phase was associated with the AHP. Early adaptation was abolished when, in the reference model, the gNapSI was blocked. The inclusion of a slow inactivation variable in the fast sodium conductance enables a late adaptation phase and also affects the early phase so, these phases are related with currents of large time constants (about 20s).