Fig. 3

Nicotinamide treatment rescues synaptic loss in hippocampal primary neurons derived from 5xFAD mice. a Representative images of dendritic spines in primary WT and 5xFAD hippocampal neurons at 18–19 DIV. The dendritic segment outlined with a white box (upper) is magnified to delineate the spine morphology (bottom) with a 3× optic zoom. The scale bars indicate 20 μm and 10 μm in the low- and high-magnification images, respectively. b Quantification of the spine densities. The dendritic spine densities were significantly reduced in neurons derived from 5xFAD mice (n = 28 neurons, one-way ANOVA) compared with those from WT mice (n = 39 neurons). Treatment with nicotinamide significantly attenuated the reduction in dendritic spine density in primary hippocampal neurons derived from 5xFAD mice (n = 17 neurons, one-way ANOVA). Data are represented as mean ± SEM. ^*p < 0.05, ^***p < 0.001 compared with mGFP-transfected WT hippocampal primary neurons; ^#p < 0.001 compared with mGFP-transfected 5xFAD hippocampal primary neurons. NA, nicotinamide; DIV, days in vitro