Fig. 4.

Lack of localized increase in [Na]_i in the vicinity of the cell plasma membrane following nsPEF exposure. Inset shows a fluorescent image of the cell loaded with 1 µm of Sodium Green. The emission intensity was measured along the dashed line, which connects the tips of nsPEF-delivering electrodes (not shown). A: The emission along the line was measured repeatedly before and after exposure to one 300 ns pulse at 5.3 kV/cm (arrow). Increased emission following exposure reflects the Na⁺ influx through the membrane. B: Individual line scans of the emission intensity immediately prior to exposure and 20 s after. The emission gain due to exposure is the arithmetic difference between these two curves. Note maximum emission gain above the center of the cell body and lack of any additional peaks close to the plasma membrane. The calibration of dye emission against [Na]_i that was used in Figure 2 does not apply to line scan measurements presented here.