Fig. 4.

Recurrent excitatory activities in the GCL of HS. (a) Flavoprotein fluorescence imaging and Timm staining in the DG. Scale bars: 1 mm (flavoprotein fluorescence imaging) and 100 μm (Timm staining). ROIs on the GCL (blue circle) were placed equidistant from the stimulation point (black filled circle). (b) Quantitative analysis of ROIs in (a). Retroactive GCL responses upon MF stimulation were significantly larger in HS (right), but not upon direct GCL stimulation (left). (c) Effect of CNQX on retroactive activities in GCL evoked by MF stimulation in HS. Flavoprotein fluorescence responses were significantly suppressed by MF stimulation, but not by direct GCL stimulation. (d) LFP at GCL upon MF stimulation before and after CNQX application. Repetitive deflections were observed only in HS, and were clearly abolished by CNQX. The numbers of spikes were compared before and after CNQX application in HS (n = 5). (e) Correlation between signal changes in GCL and width of GCL in HS. Points A and B indicated in the graph correspond to the images in the lower panels. Scale bar: 100 μm. Error bars, S.E.M. *p < 0.05, **p < 0.01; by One-way ANOVA with Tukey-Kramer test (b) or paired t-test (c, d). N.S.: not significant.