Figure 4.

Glucose deprivation increases intracellular calcium levels in astrocytes. (A) Schematic depicting in a hippocampal slice dual recordings of field excitatory postsynaptic potentials (fEPSPs) evoked by Schaffer collaterals stimulation (Stim) and astroglial calcium levels. (B–C) Sample fluorescence images recorded in the orange zone shown in (A), illustrating calcium levels of stratum radiatum astrocytes detected by Fluo-4 imaging (B), and corresponding fEPSPs traces simultaneously recorded (C) before (Control) and after 30 min of glucose deprivation. Color bar: 0–255 (arbitrary fluorescence units, 8 bits resolution). Scale bars: 10 μm (B) and 0.2 mV, 20 ms (C). (D) Quantification of simultaneous relative changes in astroglial calcium levels (ΔF/F₀ in 4 color coded astrocytes, upper panel) and fEPSP slope (white circles, lower panel) induced by glucose deprivation in a representative experiment. Scale bar (upper panel), 2%, 5 min. (E) Cross correlation analysis between the time series of fEPSP and astroglial calcium signals illustrated in (D). The high amplitude of the peak cross correlation coefficient (−0.78 at a time lag of −40 s) indicates a strong correlation between the two signals, where changes in fEPSP precede variations in astroglial calcium levels. (F) Quantification of mean peak relative changes in fEPSP slope and astroglial calcium levels (ΔF/F₀) induced by the 30 min glucose deprivation (n = 5 cells, 5 slices, 3 mice). Asterisks indicate statistical significance (***p < 0.001).