Zizyphus Enhances Cell Proliferation and Neuroblast Differentiation in the Subgranular Zone of the Dentate Gyrus in Middle-Aged Mice

Zizyphus jujuba is considered to have various physiological functions in the brain. We obtained a Z. jujuba methanol extract (ZJE) and observed its effects on neurogenesis in middle-aged mice. Twelve-month-old mice received repeated oral administrations of ZJE for 30 days. The administration of ZJE significantly increased the number of Ki67 (a marker for cell proliferation)-positive cells in the subgranular zone of the dentate gyrus of middle-aged mice. Furthermore, ZJE significantly increased doublecortin (a marker for neuroblast differentiation)-immunoreactive neuroblasts with tertiary dendrites, but not those without tertiary dendrites, in the dentate gyrus. In addition, doublecortin protein levels in the ZJE-treated groups tended to increase dose-dependently. These results suggest that the repeated supplement of ZJE may increase the hippocampal plasticity in middle-aged mice.