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, 100 mg/kg EPG was administered orally to mice for 30 days before sacrifice and 5-bromodeoxyguanosine (BrdU) was injected intraperitoneally every 8 h for 24 h 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.