Figure 2.

Astrocytic Ca²⁺ signaling evoked by photolysis enhances mEPSCs. A, Time series of intracellular Ca²⁺ increase (arrows) induced by UV photolysis (2 pulses, 30 μs length, 10 μs interval, 30 mW, beam diameter of 4 μm, the position is indicated in the 2nd frame), in a hippocampal slice loaded with NP-EGTA AM (10 μm) and rhod-2 AM (5 μm). Scale bar, 50 μm. The pseudocolor scale displays relative changes in rhod-2 emission. B, Traces of fluorescence changes in rhod-2 emission as a function of time after photolysis of NP-EGTA. The color coding of the traces matches the colored arrows in A. C, Comparison of Ca²⁺ amplitude and duration of astrocytic Ca²⁺ increases induced by photolysis in the presence and absence of the mGluR antagonists MPEP (10 μm) and AIDA (10 μm; p > 0.05, t tests, n = 5–7). D, A representative recording of a CA1 pyramidal neuron shows that photolysis of NP-EGTA in a nearby astrocyte increased the frequency of mEPSCs of a neighboring neuron. Expanded timescale traces before and after photolysis (red shaded) are displayed below. Bottom trace depicts changes in neuronal membrane potential in response to astrocytic Ca²⁺ signaling evoked by photolysis of NP-EGTA. E, Cumulative probability of amplitude and interevent intervals from recordings in D. F, Histograms comparing the effect of photolysis of NP-EGTA in astrocytes on the amplitude and frequency of mEPSCs in the absence and presence of the mGluR blocker MPEP and AIDA (*p < 0.05, paired t test before and after photolysis for each group; ^#p < 0.05, t test; n = 5–10). Right panel shows the effect of photolysis of NP-EGTA on the membrane potential of a nearby neurons (<50 μm) in the absence and presence of the mGluR blockers MPEP and AIDA or in the absence and presence of the NMDA receptor antagonists AP-5 (50 μm) and CNQX (20 μm; *p < 0.05, paired t test; ^#p < 0.05, one-way ANOVA with Bonferroni's test comparing different bath conditions; n = 4–5).