Figure 1.

Expression of EGFP in astrocytes in brain slices prepared from transgenic mice is shown in A. Scale bar, 30 μm. In B, the calibration curve for SNAFL is shown. Cells were exposed to solutions containing nigericin at known pH values ranging from 6.9 to 7.3, and the ratio of fluorescence at two excitation wave lengths (550 and 510 nm) was determined. The calibration data were fit using a linear regression equation, because we used only a small pH range close to the pKa of SNAFL. Fluo-4 loading is shown in C. Scale bar, 30 μm. The cells that stained more intensely for Fluo-4 were astrocytes. Fluo-4 is a Ca²⁺-sensitive dye, and when the population of Fluo-4 loaded cells was divided into two groups based on the intensity of Fluo-4 fluorescence in aCSF (D), only those cells with more intense uptake demonstrated increased intracellular Ca²⁺ levels after exposure to low-potassium solutions (Dallwig and Deitmer, 2002). *p < 0.05.