NGF and Alzheimer disease: In light of our previous in vitro findings that astrocytic GluN2A protects synapse against Aβ synaptotoxicity likely through NGF secreted from astrocytes, to further confirm neuroprotective role of GluN2A through regulating NGF in AD rat, we next evaluated the effects of astrocyte‐specific Grin2a knockdown on the level of β‐NGF.