Experimental time-line for the BrdU and Morris water maze experiments.

<p>C57BL/6J male mice with 1.5, 3, 6, 9, and 12 months of age received BrdU injections (200 mg/kg i.p.) every 12 hours for 3 consecutive days. On day 12, animals were pre-trained in the MWM (three trials of 60 seconds each) with the platform protruding from the water surface. Between days 13 and 15 mice were trained to locate the hidden platform in the MWM. Each day animals received two training sessions separated by a 4-hour interval. Each session was composed by two blocks (of three 60-second trials each) separated by one hour. Mice were left undisturbed between days 16 and 42 and on day 43 they received a probe test in the MWM by placing them in the water without the platform for 60 seconds and assessing the amount of time they spent in the target quadrant (where the platform used to be located). Mice were sacrificed one hour later by transcardial perfusion and their brains were processed for immunohistochemistry.