NGFR and Alzheimer disease: Together these observations suggest that the role of p75NTR in this context is extremely complex possibly also due to its two-faced role in the pathogenesis of AD and due to the fact that in gene ablation studies p75NTR is also missing during the life time of the animals, in particular during development, which could affect pruning of, e.g., cholinergic fibers into the hippocampus.