Figure 1. Longitudinal diffusion delay is reduced in CO₂/HCO₃⁻ buffer.

Acid is diffused into a rabbit myocyte from a patch pipette. Standardized longitudinal positions of pipette and regions of interest (ROIs) are shown in a confocal, calibrated ratiometric SNARF image (right). Distance from pipette to centre of ROI 1: 15 μm; ROI 1 to ROI 2: 40 μm. Main graph shows the time course of acid loading averaged within the ROIs. Inset shows the initial period after break-in at higher amplification. To help identify the arrival time of pH_i at the 0.1 threshold, polynomial fits (5th order) were applied to each curve over the first 2.3 min. Dashed lines indicate time delay between the two ROIs estimated at a threshold fall of pH_i (ΔpH_i) of −0.1 units. A, Hepes-buffered superfusate. B, 5 % CO₂/HCO₃⁻-buffered superfusate.