Figure 1
Cl− diffusion is slower in spiny than in smooth dendrite-like cylinders.
(A) Top: Schematic representation of simulated morphology. Spines were randomly attached to a dendritic cylinder (700 μm length, 1 μm diameter). Bottom: Normalized Cl− concentration profiles at t = 4000 ms in the dendritic cylinder with different spine densities. Cl− diffusion was triggered by an initial increase in Cl− concentration (from 5 to 10 mM at t = 0 ms) within a 1 μm compartment at the center of the dendrite. (B) The spatial variance of Cl− concentration as a function of time decreased with increasing spine density. The dotted line denotes the linear time dependence of obstacle-free, unhindered Cl− diffusion. The time dependence of spatial variance indicates a slowdown of diffusion in spiny dendrites. At each time step, the normalized Cl− concentration profiles were used to determine the spatial variance. (C) The instantaneous apparent diffusion coefficient (Dapp) was computed from spatial variance and divided by the diffusion coefficient for Cl− (DCl = 2 um2/ms). (D) Calculated values of tortuosity as a function of spine density. The tortuosity increased with increasing spine densities.
