NTN1 and Alzheimer disease: Within this same AD rat model, both serum and CSF concentrations of netrin-1 were decreased (Sun et al., 2019), while an exogenous application of netrin-1 was found to regulate Aβ peptide production, oligomerization and clearance in animal models of AD (Lourenço et al., 2009; Spilman et al., 2016; Shabani et al., 2017; Zamani et al., 2019).