NGF and Alzheimer disease: Despite these positive results, other studies have not systematically shown direct interference of BDNF and NGF in the formation of Aβ plaques and neurofibrillary tangles in the development of AD (Capsoni et al., 2000; Arancibia et al., 2008; Castello et al., 2012; Xiong et al., 2015; Braun et al., 2017; Wang et al., 2019), which can be explained by the differences in animal models or methodologies employed.