BDNF and memory impairment: In conclusion, it seems that the protective effect of orally administered ZM essential oil on learning and memory impairment due to ICV injection of Aβ 1–42 in rats, as shown by MWM task outcome and Congo red staining, is at least partly via reducing hippocampal AchE activity accompanied by enhancement of BDNF levels without a change in antioxidant status.