NTRK1 and Alzheimer disease: In fact, besides the role of reduced retrograde transport of NGF [36,83] and the new evidence obtained in adult anti-NGF transgenic mice directly linking NGF deprivation to cholinergic deficits [57,85], there might be also a potential role of proNGF in triggering cell death through the p75 receptor [90] whose levels are increased in AD patients along with decreased TrkA expression [95,96].