The synaptic composition in TgF344-AD rats exhibited variation, characterized by reduced levels of the presynaptic marker synaptophysin, decreased density of serotonin receptors at 18 months, along with higher levels of prostaglandin D2 receptors in 11-month-old transgenics, altogether suggesting vulnerability to synapse loss in AD pathology [59–61]. This evidence concerns the gene SYP and Alzheimer disease.