Figure 4.

Decreased DGC activation during postnatal development. A, Top, Schematic of a hippocampal slice depicting the imaged area in the DG and a Fura2-loaded DG of a P12 mouse (370 μm × 370 μm). Bottom, Image of P12 and P60 DGCs, with ROI created on a random sample of cells (orange) (90 μm × 200 μm). Numbers denote cell identification with time-resolved fluorescence responses depicted in B. B, Representative traces of time-resolved calcium imaging responses for the ROI in the P12 and P60 images in A. The dotted line indicates the time when PP stimulation (400 μA) occurred. An asterisk indicates detection of a calcium transient. C, Plot of the percentage DGC activation by PP stimulation for P12, P22, and P60 animals. Note the decrease in cell activation with postnatal development. p < 0.0001 for the animal age factor (ANOVA). *p < 0.05, significant differences between P12 and P22 (Tukey's multiple-comparison post hoc testing). **p < 0.01, significant differences between P12 and P60 groups (Tukey's multiple-comparison post hoc testing). P12: n = 322 PTX-active cells in 10 imaged regions; P22: n = 198 in 10 imaged regions; P60: n = 239 of 12 imaged regions.