Induction of cell proliferation and neuroblasts in the subgranular zone of the dentate gyrus by aqueous extract from Platycodon grandiflorum in middle-aged mice.

In the present study, we observed the neurogenic effects of an aqueous extract from the root of Platycodon grandiflorum (EPG) in middle-aged (12-month-old) mice. For this, 100mg/kg EPG was administered orally to mice for 30 days before sacrifice and 5-bromodeoxyguanosine (BrdU) was injected intraperitoneally every 8h for 24h on the day prior to sacrifice. The increase of neurogenesis was estimated by immunohistochemical staining for cellular proliferation markers (BrdU and Ki67) and a marker for neuroblasts (Doublecortin, DCX). These markers were detected in the subgranular zone of the dentate gyrus in vehicle- and EPG-treated groups. The number of BrdU-, Ki67- and DCX-positive cells in the EPG-treated group was significantly increased compared to that in the vehicle-treated group. In addition, DCX-positive cells in the EPG-treated group showed well-developed processes. These results suggest that the number of neuroblasts is increased by the repeated treatment of EPG in middle-aged mice.