Cell proliferation is significantly decreased by age in the mouse hippocampal DG.

<p>POMC-EGFP transgenic mice were sacrificed at 1, 1.5, 2, 2.5, 3, 4, 6, 12, 18, 24 months of age by transcardial perfusion and their brains were processed for immunohistochemistry for the endogenous cell proliferation markers Ki-67 (A-C) and PCNA (D-F). Age induced a significant decline in the expression of both Ki-67 (A-C) and PCNA (D-F). An abrupt reduction in cell proliferation was detected early on (between 1.5 and 3 months of age) with both markers. Data are presented as means ± SEM. (A) *** <i>p</i> < 0.001 between 1 or 1.5 and 2 months, between 2 and 3 months, and between 2.5 and 4, 6, 12, 18 or 24 months. (D) ** <i>p</i> < 0.01 between 2 and 4 months, and between 3 and 6 months, *** <i>p</i> < 0.001 between 1 or 1.5 and 2 months, and between 3 and 12, 18, or 24 months. See text for additional statistical details. Representative sections of the DG processed for Ki-67 (B, C) and PCNA (E, F) immunohistochemistry in 1- (B, E) and 24- (C, F) month old POMC-EGFP mice. Black arrows indicate either Ki-67- (B) or PCNA- (E, F) immunopositive cells in the DG of 1- (B, E) and 24- (F) month old mice. Scale bars = 100 µm.