Synaptic vesicle clouds increase at 7 DPI and mossy cell somata hypertrophy following mild TBI. In anterior hilus, mossy cell soma area increased at 7 DPI (d) and 30 DPI (g) compared to sham (a). Histograms of mossy cell area (j, l, n) illustrate a rightward shift of the data distribution at 7 DPI and 30 DPI compared to sham. Sum intensity of synapsin in anterior hilus increased at 7 DPI (e) compared to sham (b). Synapsin labeling then decreased at 30 DPI (h) compared to 7 DPI. Histograms of synapsin sum intensity (k, m, o) show the frequency of higher synapsin sum intensities at 7 DPI compared to sham and 30 DPI. (c, f, i) display the merge of synapsin and MAP2 channels (scale bar = 25 μm). In posterior hilus, mossy cell soma area increased at 30 DPI (v) compared to sham (p) and 7 DPI (s). Histograms of mossy cell area (y, aa, cc) display a rightward shift of the data distribution at 30 DPI compared to sham and 7 DPI. Sum intensity of synapsin in posterior hilus increased at 7 DPI (t) compared to sham (q) then decreased at 30 DPI (w). Histograms of synapsin sum intensity (z, bb, dd) display the frequency of higher synapsin intensities at 7 DPI compared to sham and 30 DPI. r, u, and x display the merge of synapsin and MAP2 channels (scale bar = 25 μm). Data are represented as the percentage of total cells. Black vertical lines are drawn at the mean value for each experimental group. The shift in cell area or synapsin sum intensity is represented by colored horizontal bars, which indicate the percentage shift