NTRK1 and Alzheimer disease: Changes in the cholinergic system during progression of AD have been documented by assessing the major functional components of cholinergic cells and signaling: the acetylcholine-synthesizing and -degrading enzymes, ChAT and acetylcholinesterase (AChE), respectively, VAChT that transports ACh into the vesicles, mAChRs and nAChRs, and the requirement of cholinergic neurons to receive neurotrophic support by NGF mediated by high- (TrkA) and low-affinity (p75NTR) receptors for survival (Hampel et al., 2018).