NPY and Alzheimer disease: NPY levels are reduced in AD patients and mouse models [26,27,28], causing a decline in the neuroprotective effects exerted by the neuropeptide, including its ability to attenuate the toxic accumulation of Aβ [28], prevent calcium-induced accumulation and excitotoxicity in presynaptic terminals [105], regulate immune cell function [106] and induce neurogenesis in areas which undergo large neuronal loss, such as the hippocampus [28,107].