NGF and Alzheimer disease: Nerve growth factor (NGF) was studied therapeutically to activate TrkA in models of Alzheimer disease (AD) (Schindowski et al., 2008; Cuello et al., 2010), and ageing (Mufson et al., 2000; Bruno et al., 2004; Saragovi, 2005), or Down syndrome (Sendera et al., 2000; Dorsey et al., 2006), models with cholinergic deficits and memory impairment.