Distributions of ion channels.
(A) Schematic of segment groups in a toy ball-and-stick model, each with a specific distribution as a function of distance from the soma. (B) Panel for creating a channel group. (C) Distribution parameters adjusted using the group’s widgets. (D) Graphs showing uniform Na channel conductance distribution (left) and a modified graph (right) where Na conductance in the selected region (dashed line) is decreased by 60%. Schematic electrodes indicate recording positions. Morphology from Park et al., 2019 [Park et al., 2019]. (E) Example of an exponential distribution for the HCN (Ih) channels (Inset - original morphology [Poirazi et al., 2003]). (F) Example of a calcium ”hot spot” (red) (Inset - original morphology [Hay et al., 2011]). (G) Top: Sodium-driven backpropagation-activated action potentials (BAPs). A current step of 160 pA is applied at the soma. Bottom: Expanded time scale for the two scenarios in (D), showing failure of BAP spike initiation (blue arrow) in the region with decreased sodium conductance. (H) Top: Distribution of maximal conductance of HCN channels as a function of distance from the soma. Bottom: Voltage sag produced by HCN channels. Current injected at the somatic (−200 pA, 200 ms) and then, after 300 ms, at the dendritic electrode at the distal apical trunk (697 µm from the soma). Dashed trace: blocking HCN channels, modeled as 80% decrease in channel conductance. (I) Top: Distribution of maximal conductance of calcium channels as a function of distance from the soma. Bottom: A dendritic calcium plateau potential triggered by dendritic step current injection (500 pA, 100 ms) at the calcium ”hot-spot”, leading to somatic firing. Somatic traces are shown in orange, dendritic in blue (and gray).