Fig. 4: Reduced expression of post-synaptic protein PSD-95 in ELA mice.

A–C The protein levels of PSD-95 and presynaptic vesicle protein Syn in the PrL. The optical densities of bands corresponding to PSD-95 and Syn were normalized to respective actin levels and expressed as a percentage of controls. ELA mice had a decreased expression of PSD-95 (F_1,22 = 8.994; ^**P < 0.01) but not Syn (P = 0.83). D–K Effect of ELA on synaptic puncta in the PrL. Representative z-stack (0.2 µm × 10) confocal images from layers V-VI of control and ELA mice (D, E and G, H). Decreased number of total PSD-95-ir puncta in layers II-III and V-VI in ELA mice versus controls (F_1,22 = 54.79; ^**P < 0.01) (F), but limited impact of ELA on Syn (F_1,22 = 4.47; P > 0.05) (I). Size distribution of PSD-95-ir puncta (J, K) suggested loss of synapses, particularly those at a size of 0.1-0.2 µm³ or 0.45–0.60 µm³ in ELA mice (post hoc test, ^*P < 0.05, ^**P < 0.01). Scale bars = 5 µm (D, E and G, H). L, M Reduced PSD-95 expression correlates with poor working memory performance in ELA mice. Positive correlations were observed between the spontaneous alternation in a T-maze and the number of total PSD-95-ir puncta in layers II-III (Pearson r = 0.69, P < 0.01) and V-VI (r = 0.62, P < 0.01) (L). A positive correlation was also observed between the memory performance and the number of small PSD-95-ir puncta (0.1–0.2 µm³) in both ELA mice (r = 0.62 and 0.58 in II-III and V-VI, respectively, P < 0.05) and control mice (r = 0.60 and 0.71 in II-III and V-VI, respectively, P < 0.05).