FoxO3a immunoreactivity is markedly decreased in the dentate gyrus, not the hippocampus proper, of the aged gerbil

Forkhead box O 3a (FoxO3a) has been known to link with aging process and senescence. In this study, we investigated the age-related changes of FoxO3a in the gerbil hippocampus using immunohistochemistry and western blot analysis. In the postnatal month 3 (PM 3) group, FoxO3a immunoreactivity was well detected in pyramidal cells of the hippocampus proper, and granule cells of the dentate gyrus. FoxO3a immunoreactivity in the pyramidal cells of the hippocampus proper was not changed until PM 24. However, in the dentate granule cells, FoxO3a immunoreactivity was much decreased in the dorsal blade, not the ventral blade, of the granule cell layer in the PM 6 and 12 groups compared to the PM 3 group. At PM 24, FoxO3a immunoreactivity in the granule cells was hardly detected. Western blot analysis showed that FoxO3a level was significantly decreased in the PM 24 group. These results indicate that FoxO3a immunoreactivity and levels are markedly decreased in the dentate gyrus of the aged gerbil hippocampus.

Research highlights
► FoxO3a immunoreactivity was not changed in hippocampal pyramidal cells during normal aging.
► In the adult, FoxO3a immunoreactivity in dentate granule cells was much decreased only in the dorsal blade.
► In the aged, FoxO3a immunoreactivity in dentate granule cells was hardly detected in both blades.