NGF and Alzheimer disease: Many studies provide evidence that ginsenoside Rb1 possesses potent neuroprotective effects on cortical neurons and dopaminergic neurons against glutamate toxicity [4,5], protects against cerebral ischemia in rats by promoting neurogenesis [6], enhances nerve growth factor (NGF)-mediated neurite outgrowth of cultured chick embryonic dorsal root ganglia [7], prevents MPP+-induced apoptosis in PC12 cells [8], inhibits neuroinflammations in a rat model of Alzheimer’s disease [9], and improves spatial learning and increases hippocampal synaptophysin level in mice [10].