Lesion-Induced Alterations in Astrocyte Glutamate Transporter Expression and Function in the Hippocampus
Figure 6
Sodium changes induced by activation of glutamate uptake. (a) Staining of astrocytes by colabeling with SR101 and SBFI. Left: epifluorescence image of the CA1-area of an SR101-loaded organotypic slice. Center: SBFI fluorescence taken from the same area. Right: overlay. SBFI-loaded, SR101-positive astrocytes appear in white (arrowheads). StrP, stratum pyramidale; StrR, stratum radiatum; scale bar: 20 μm. (b) Left: calibration of SBFI fluorescence in an astrocyte. Depicted is the change in intracellular SBFI fluorescence ratio in the calibration solutions containing ionophores and in response to stepwise changes in the sodium concentration. Right: mean values ± S.E.M. of the normalized changes in SBFI fluorescence at different sodium concentrations. The black line represents a linear fit of the data points between 10 and 40 mM sodium, illustrating that a 10% change in SBFI fluorescence represents a change in the sodium concentration by 5.5 mM. (c) Sodium transients in a single astrocyte induced by 500 ms applications of D-aspartate at different concentrations. (d) Mean values ± S. E. M. () of the peak amplitude of sodium transients at different concentrations of D-aspartate. The curve represents a sigmoidal fit of the data.
