Figure 1. Endogenous buffer capacity is enhanced in aging CA1 pyramidal neurons. Widefield image of a CA1 pyramidal neuron loaded with 200 μm OGB-1 (bottom left). White box, Region of interest (ROI) where calcium transients were measured, ∼40 μm from the soma. Dotted white boxes, Background regions. Scale bar, 40 μm. A, Example calcium transients evoked by an action potential in neurons loaded with different concentrations of OGB-1 and measured using a CCD camera. B, Reciprocal amplitude of calcium transients (1/Δ[Ca2+]) plot against exogenous buffer capacity (κB). The R values and the slopes of the linear extrapolation were 0.771 and 0.000,124 (p values < 0.0001) for young, and 0.742 and 0.000,078 (p values < 0.0001) for aging. Each point represents one neuron loaded with 25, 50, 75, 100, 150, or 200 μm OGB-1 (29 neurons from 12 young adult rats, 24 neurons from 9 aged rats). C, No significant difference was observed in the peak amplitude of calcium transients evoked with single action potentials in CA1 neurons from young and aging rats that were loaded with 25 μm OGB-1 (5 neurons from 3 young adult rats, 6 neurons from 5 aged rats). The figure illustrates the data obtained for each individual neuron (small circles) and the mean ±SEM (larger circle). D, Resting calcium concentration in young and aging CA1 neurons (29 neurons from 12 young adult rats, 24 neurons from 9 aged rats).