Novel effects of Nelumbo nucifera rhizome extract on memory and neurogenesis in the dentate gyrus of the rat hippocampus

Memory enhancement is a matter of concern in general, and in particular to people suffering from cognitive dysfunction. In this study, we investigated the effect of Nelumbo nucifera rhizome extract on learning and memory function. A step-through passive avoidance test was performed with Wistar rats. In addition, immunohistochemistry was used to investigate cell proliferation and differentiation in the dentate gyrus of the hippocampus. The methanol extract of N. nucifera rhizome (MNR) resulted in significant improvements of memory functions and neurogenesis in the dentate gyrus. In the passive avoidance test, the retention time of MNR-treated rats was significantly longer than that of controls. Immunohistochemical analyses using BrdU, Ki-67, and DCX showed significantly increased cell proliferation and cell differentiation in the dentate gyrus. These results suggest that N. nucifera rhizome extract may improve learning and memory with enhancing neurogenesis in the DG of the hippocampus.