Fig. 7. Astrocyte oscillations mediate repetitive [Ca2+]i increases in neurons.A, [Ca2+]i repetitive increases in one pyramidal hippocampal neuron after three consecutive stimulations with 10 μmt-ACPD. The response to t-ACPD was abolished by NBQX/d-AP5. Before the second t-ACPD application, the slice was perfused for 10 min with NBQX andd-AP5, both at 50 μm. Before the thirdt-ACPD stimulation, the slice was perfused with normal saline for 20 min. B, [Ca2+]i oscillations in one astrocyte adjacent to the neuron in A after the threet-ACPD stimulations. C, Reduction by NBQX and d-AP5, both at 50 μm, in the amplitude of the t-ACPD-induced [Ca2+]i increase after the second episode of stimulation from a hippocampal pyramidal neuron and its recovery in the third t-ACPD stimulation performed in the absence of the iGluR blockers after a time interval of 20 min.D, Relative change in the amplitude of the [Ca2+]i increase in each neuron after the second t-ACPD stimulation performed in the absence (control) or presence of NBQX/AP5, as compared with the first t-ACPD stimulation.Filled symbols represent the values of the mean ± SE. The mean change in the response from NBQX/d-AP5 neurons was significantly different from that from control neurons; **p < 0.0001; t test.E, Whole-cell recordings of EPSCs evoked on a CA1 pyramidal neuron by stimulation of Schaffer collaterals at 0.2 Hz. Three consecutive EPSCs and the average trace from eight consecutive EPSCs (bottom traces) before and after the TeNT application are shown. Despite increasing the intensity of the stimulus (note the increased amplitude of the stimulus artifact), we recorded no EPSCs 20 min after TeNT. F, Relative change in the amplitude of the [Ca2+]i increase after the second t-ACPD stimulation, as compared with the first t-ACPD stimulation, in each neuron from slices incubated for 40–60 min with TeNT. The second t-ACPD stimulation was performed in the presence of NBQX/d-AP5, both at 50 μm. The mean change in the response from these neurons was significantly different with respect to that from control neurons (**p < 0.0001; t test), but not with respect to that from NBQX/d-AP5 neurons from slices not treated with TeNT. Symbols are as in D.