High Speed Two-Photon Imaging of Calcium Dynamics in Dendritic Spines: Consequences for Spine Calcium Kinetics and Buffer Capacity
Figure 2
Differing estimates of endogenous buffer capacities in spines and small dendrites.
A. Example image of a targeted dendrite and spine pair. Dotted line indicates line-scanned region. B. Back-propagating AP trains were induced to cause maximal dye-saturating calcium indicator fluorescence changes in both spines and dendrites to calculate fmax. Upper panel, AP train. Lower panels, example maximal fluorescence plateau levels. Darker line indicates boxplot smoothed trace average used for fmax calculations. C. Examples of average δf and δfmax signals following single AP and AP trains respectively, from spines and dendrites. Arrow indicates onset of stimulation. D. Inverse peak calcium change (Δ[Ca2+]AP −1) following a single AP versus added buffer capacity, κD, for dendrite (blue, upper panel) and spine (red, lower panel). Average values (mean±SEM) for each added buffer concentration (33, 50, 62.5, 75, 90, 100 µM) are plotted over individual data points (open circles) (n = 35). Endogenous buffer capacity (κE) was read off from the intersection of the linear fit with the x axis at zero level of added dye. [Spine κE = 19 UCI:40, LCI:4; Dendrite κE = 62 UCI:172, LCI:15). 95% confidence intervals are shown in dotted outlines.