Asymmetry in Signal Propagation between the Soma and Dendrites Plays a Key Role in Determining Dendritic Excitability in Motoneurons
Figure 4
Sensitivity of cellular excitability to the VA factors.
Using the same reduced model and ramp stimulation protocols used in Figure 2(H) & (I), F-Isoma and F-Gsyn relationships were simulated while varying individual VA factors independently. (A), (B). F-Isoma curves with VASDDC decreased by 4.7% and increased by 20.4% from its original value (0.76). Circled letters, IS1 (8.1 nA) and IS2 (19.8 nA), on vertical gray lines indicate decreased and increased current threshold for initiating firing acceleration as a result of changing the VASDDC. Black arrows indicate the rising and falling phase of triangular current stimulation to the soma. (C), (D). F-Gsyn curves with VASDDC changed by the same variation (%) as applied to (A) and (B). Vertical gray arrows indicate increased (about 0.055 mS/cm2, left column) and decreased (about 0.029 mS/cm2, right column) threshold-Gsyn for the firing acceleration as a result of varying the VASDDC. Black arrows indicate the rising and falling phase of triangular change in Gsyn at the dendrite. (E). The percent variation in individual VA factors (VASDDC, VADSDC, VASDAC) to produce the firing acceleration at either IS1 or IS2. 0% represents the original values of VA factors and minus sign in the ordinate indicates the decrease in VA factor values. (F). Relationship of threshold current (IS) for the firing acceleration and the percent variation in DC VA factors. Data points were fitted to a linear regression line. Note that RN for the reduced model was set to be 1.29 MΩ.
