Figure 6From: Transgenic APP expression during postnatal development causes persistent locomotor hyperactivity in the adultDelaying the onset of APP overexpression attenuates hyperactivity but not anxiety in the open field assay. An independent cohort of animals was tested by open field assay at a single time point following 6 mo of APP overexpression. A A fraction of APP/TTA mice in both juvenile and adult onset groups show extreme hyperactivity, traveling >500 m in 30 min (5/15 juvenile onset, 4/26 adult onset), but most cover distances closer to the average of the other genotypes. B While both adult- and juvenile-onset APP/TTA mice travel greater average distances than other genotypes (p < 0.0001), delaying the onset of transgene expression significantly diminished hyperactivity compared to juvenile onset (***p < 0.001). C Juvenile-onset APP/TTA mice travel a smaller fraction of their total path within the center of the open field arena than control mice (p < 0.001 vs. NTG and APP, p < 0.01 vs. TTA). This difference is not normalized by delaying the onset of transgene expression. The only genotype for which dox rearing significantly altered path in center was APP (*p < 0.05). D A separate cohort of NTG and APP/TTA mice was reared on dox until 6 wk of age and then tested in the open field 8 mo later. Data from the 8 mo adult-onset mice are plotted alongside 6 mo juvenile-onset mice taken from panel A to provide a comparison of open field activity in mice matched for amyloid load rather than duration of APP overexpression. Again, delaying transgene onset reduces the fraction of mice displaying extreme hyperactivity (2/37 adult onset, 5/15 juvenile onset). E Average distance traveled is significantly reduced by delaying transgene onset (***p < 0.001). While open field activity of juvenile-onset APP/TTA mice is significantly higher than their NTG siblings (p < 0.05), adult-onset APP/TTA mice are no different than age-matched NTG controls (p > 0.05). F Despite significant attenuation of locomotor hyperactivity, delaying APP overexpression does not alter anxiety measured as % path in the center of the open field arena.Back to article page