Figure 3

Proliferation and differentiation was significantly enhanced in the LTP(+)-stimulated hippocampus. The effect of LTP induction on precursor cell proliferation and differentiation was assessed by BrdU incorporation. BrdU was administered 4 days after LTP induction, and mice were killed 30 min (proliferation) or 1 week (differentiation) after the last BrdU injection. (a) The number of BrdU-positive cells per length of the dentate gyrus (mm) was significantly enhanced in stimulated hippocampi of the LTP(+) group, relative to the unstimulated hemisphere (P=0.0381, n=5, Student's paired t-test). Furthermore, there were a greater number of BrdU-positive cells following LTP induction, compared with the CPP group (P=0.0096, n=5, Student's unpaired t-test) and LFS group (P=0.0028, n=6, Student's unpaired t-test). (b) Following LTP induction, the number of BrdU/DCX double-positive cells per perimeter length of the dentate gyrus (mm) was significantly enhanced in the stimulated hippocampus compared with the control hippocampus (P=0.0053, n=6, Student's paired t-test). BrdU/DCX-double labeling also revealed a significantly greater number of neurons in the stimulated hippocampi of the LTP(+) group compared with the stimulated hippocampi of the CPP (P=0.0121, n=6, Student's unpaired t-test) and the LFS (P=0.0084, n=6, Student's unpaired t-test) groups. (c) Representative maximum intensity projection image of BrdU (red) and DCX (green) immunostaining reconstructed from 40 optical sections of the LTP-stimulated hippocampus of the LTP(+) group. Inset shows a higher magnification, orthogonal view image of the indicated region in a single optical section, to illustrate that individual cells were double labeled. Scale bar: 50 μm in main image, 20 μm for inset. ^*P<0.05, ^**P<0.01. Abbreviations: BrdU, 5-bromo-2′-deoxyuridine; C, control side; CPP, 3-(2-carboxypiperazin-4-yl)propyl-1-phosphonic acid; DCX, doublecortin; LTP, long-term potentiation; S, stimulated side.