BDNF and Alzheimer disease: Further, the protein and mRNA levels for BDNF and TrkB are significantly decreased in AD (Ferrer et al., 1999; Ginsberg et al., 2010), and previous studies have shown that treatment with BDNF restored spine abnormalities in AD mouse models in vivo (de Pins et al., 2019) and in vitro (Meng et al., 2013).