Essential oils from two Allium species exert effects on cell proliferation and neuroblast differentiation in the mouse dentate gyrus by modulating brain-derived neurotrophic factor and acetylcholinesterase

Background: In the present study, we investigated the effects of oil products from two Allium species: Allium sativum (garlic) and Allium hookeri (Chinese chives) on cell proliferation and neuroblast differentiation in the mouse dentate gyrus. Methods: Using corn oil as a vehicle, the essential oil from garlic (10 ml/kg), or Chinese chives (10 ml/kg) was administered orally to 9-week-old mice once a day for 3 weeks. One hour following the last treatment, a novel object recognition test was conducted and the animals were killed 2 h after the test. Results: In comparison to the vehicle-treated group, garlic essential oil (GO) treatment resulted in significantly increased exploration time and discrimination index during the novel object recognition test, while Chinese chives essential oil (CO) reduced the exploration time and discrimination index in the same test. In addition, the number of Ki67-immunoreactive proliferating cells and doublecortin-immunoreactive neuroblasts significantly increased in the dentate gyrus of GO-treated animals. However, administration of CO significantly decreased cell proliferation and neuroblast differentiation. Administration of GO significantly increased brain-derived neurotrophic factor (BDNF) levels and decreased acetylcholinesterase (AChE) activity in the hippocampal homogenates. In contrast, administration of CO decreased BDNF protein levels and had no significant effect on AChE activity, compared to that in the vehicle-treated group. Conclusions: These results suggest that GO significantly improves novel object recognition as well as increases cell proliferation and neuroblast differentiation, by modulating hippocampal BDNF protein levels and AChE activity, while CO impairs novel object recognition and decreases cell proliferation and neuroblast differentiation, by reducing BDNF protein levels in the hippocampus.