Apid Report Eonatally Born Granule Cells Numerically Dominate Dult Mice Dentate Gyrus

bstract—Hippocampal granule cells (GCs) are continuously enerated in the subgranular zone of the dentate gyrus (DG) nd functionally incorporated to dentate neural circuits even n adulthood. This raises a question about the fate of neonaally born GCs in adult DG. Do they exist until adulthood or re they largely superseded by adult-born GCs? To investiate this question, we examined the contributions of postnaally born GCs to the adult mouse DG. C57BL/6 mice were rouped in three different postnatal (P) ages (group 1: P0, roup 2: P7, and group 3: P35) and received a daily bromodexyuridine (BrdU) injection for three consecutive days (P0/ /2, P7/8/9, and P35/36/37, respectively) to label dividing cells. t 6 months old, hippocampal sections were prepared from he animals and immunostained with anti-BrdU antibody and n antibody against the homeobox prospero-like protein rox1, a marker of GCs. We defined BrdUand Prox1-double ositive cells as newborn GCs and analyzed their density and istribution in the granule cell layer (gcl), revealing that neworn GCs of each group still existed 6 months after BrdU injecions and that the density of GCs born during P0-2 (group 1) was ignificantly higher compared with the other groups. Although he density of newborn GCs in the each group did not differ etween male and female, the radial distribution of them in gcl howed some differences, that is, male newborn GCs localzed toward the molecular layer compared with female ones n group 1, while to the hilus in group 2. These results sugest that GCs born in early postnatal days numerically domnate adult DG and that there exist sex differences in GC ocalizations which depend on the time when they were born. 2007 IBRO. Published by Elsevier Ltd. All rights reserved.