A. Representative cfos immunostained coronal sections of dorsal and ventral DG and CA3 in adult and middle aged mice taken from home cage. Fluoxetine treatment 18mg/kg/day for 28 days. B. Quantification of c-fos positive cells. Adult n=3 (VEH), 5 (FLX) mice per group, dDG p=0.0008, vDG p=0.0326, dCA3 p=0.0055, vCA3 p=0.0067; middle-aged n=3 (VEH), 4 (FLX), dDG p=0.0009, vDG p=0.0552, dCA3 p=0.0052, vCA3 p=0.1973). Results are expressed as mean (±SEM). *, P<0.05; **, P<0.01; *** P<0.001. Scale bar 100μM.