A new description for sodium channel gating model based on macroscopic ionic currents in dissociated cerebellar Purkinje neurons

An important task in the application of state-based models to the analysis of ion dynamics is the determination of a realistic gating kinetics of the channel under investigation. Developing a realistic gating model based on measurements involves two tasks. The first task is selection of an appropriate gating model that specifies the number of states and the rate constants. The second task is determination of best parameters within the rate constants. Based on voltage-clamp and resurgent currents, a state model for gating kinetics of sodium channel in dissociated cerebellar Purkinje neurons from rats is developed by Raman and Bean. In this study, we modified the description of this model to incorporate action potential evoked sodium current in addition to voltage-clamp and resurgent currents. The improved model includes several modifications made in the number of states and channel rate constants. The model parameters are determined using trial-and-error procedure to minimize the error between model responses and three experimental data sets. The model reproduces quantitatively all features of the experimental data sets, with minor discrepancies.