Figure 1. Fluoxetine treatment increases progenitor proliferation and survival of adult-born neurons in adult but not middle-aged mice.

A. Representative MCM2 immunostained coronal hippocampal sections of adult and middle-aged mice following 4 weeks of fluoxetine treatment. B. Fluoxetine-treated (18mg/kg/day for 28 days) adult mice, but not fluoxetine-treated middle-aged mice, show increased granule cell layer MCM2 positive cells. Adult n=3 (VEH), 5 (FLX) mice per group, p=0.0315, middle-aged n=3 (VEH), 4 (FLX), p=0.9846). C. BrdU (150 mg/kg) was administered i.p. one week after the start of Fluoxetine treatment. Representative BrdU immunostained coronal hippocampal sections of adult and middle-aged mice 3 weeks following BrdU injection. D. Fluoxetine-treated adult mice, but not fluoxetine-treated middle-aged mice, show increased granule cell layer BrdU positive cells. (Adult n=3 (VEH), 4 (FLX) mice per group, p=0.0530, middle-aged n=3 (VEH), 4 (FLX), p=0.3868). E. Representative DCX immunostained coronal hippocampal sections of adult and middle-aged mice after 4 weeks of Fluoxetine treatment. Middle-aged mice exhibit a dramatically reduced population of young adult-born neurons. F. Adult mice receiving fluoxetine show a trend toward increased young adult-born neurons, whereas fluoxetine treatment in middle-aged mice does not change the population of young adult-born neurons. (Adult n=3 (VEH), 5 (FLX) mice per group, p=0.0606, middle-aged n=3 (VEH), 4 (FLX), p=0.8092). G. High magnification image of DCX immunostained young adult-born neurons with tertiary dendrites. Both adult and middle-aged mice treated with fluoxetine show an increased percentage of the DCX positive population with tertiary dendrites. (Adult n=3 (VEH), 5 (FLX) mice per group, p=0.0247, middle-aged n=3 (VEH), 4 (FLX), p=0.0680). Results are expressed as mean (±SEM). P<0.05 *. Scale bar: 100μ M.