Fluoxetine delays the cognitive function decline and synaptic changes in a transgenic mouse model of early Alzheimer's disease

Alzheimer's disease (AD) is a progressive neurodegenerative disorder associated with cognitive decline. Previous studies have reported that the syndrome of AD begins with subtle alterations in hippocampal synapses prior to frank neuronal degeneration. It has recently been reported that fluoxetine (FLX) shows positive effects on AD patients who have depression and anxiety. However, it is unclear whether FLX can affect the pathogenesis of AD mice in the early stage of AD. To address this question, 8-month-old male APP/PS1 double-transgenic AD mice were administered a 10-week course of FLX (10 mg/kg/day) injections. Then, spatial learning and memory were evaluated using a Morris water maze test. Immunohistological staining and an unbiased stereological method were used to estimate the total number of dendritic spine synapses in the hippocampus. We found that FLX significantly shortened the mean escape latencies of the 10-month-old mice; reduced the elevated levels of soluble A beta 40, A beta 42, and amyloid plaques in the hippocampus; and prevented the decrease in dendritic spine synapses and in postsynaptic protein PSD-95 density in the dentate gyrus, CA1/2 and CA3 regions of the hippocampus. Our results indicate that reversing synaptic impairment might be considered a promising therapeutic approach for alleviating the cognitive deficits associated with early AD. Moreover, our results suggest that FLX may be a safe and effective drug for delaying the progress of AD, which might provide a starting point for further research into new preventative measures and treatments for AD.