Effects of allantoin on cognitive function and hippocampal neurogenesis.

Allantoin is contained in Nelumbo nucifera (lotus) and a well-known cosmetic ingredient reported to have anti-oxidative and anti-inflammatory activities. In the present study, we investigated whether allantoin affects cognitive function in mice. The subchronic administration of allantoin (1, 3 or 10 mg/kg, for 7 days) significantly increased the latency time measured during the passive avoidance task in scopolamine-induced cholinergic blockade and normal naïve mice. Allantoin treatment (3 or 10 mg/kg, for 7 days) also increased the expression levels of phosphorylated phosphatidylinositide 3-kinase (PI3K), phosphorylated protein kinase B (Akt) and phosphorylated glycogen synthase kinase-3β (GSK-3β). Doublecortin and 5-bromo-2-deoxyuridine immunostaining revealed that allantoin significantly increased the neuronal cell proliferation of immature neurons in the hippocampal dentate gyrus region. In conclusion, allantoin has memory-enhancing effects, and these effects may be partly mediated by the PI3K-Akt-GSK-3β signal pathway. These findings suggest that allantoin has therapeutic potential for the cognitive dysfunctions observed in Alzheimer's disease.