CPE regulates the BDNF-induced spine growth in hippocampal neurons. A, Confocal image of a representative GFP-transfected hippocampal neuron (green). Bottom, Enlarged image of the framed region indicating the different dendritic spines. B, Hippocampal neurons expressing GFP at DIV 18–21 were pretreated with TAT-Con (5 μm) or TAT-CPE452-466 (5 μm) for 30 min, respectively. Then, neurons were stimulated with glycine (10 min) and/or BDNF (30 min). Higher magnification views of representative segments of dendrites from the neurons. Scale bar, 2 μm. C, Quantification of spine density, expressed per 10 μm of dendrite in B (two-way ANOVA with Bonferroni's multiple comparisons test, F(2,18) = 1.263, Ctr-TAT-Con vs BDNF-TAT-Con, **p = 0.0014; Ctr-TAT-Con versus Gly+BDNF-TAT-Con, ****p < 0.0001; BDNF-TAT-Con vs Gly+BDNF-TAT-Con, #p = 0.0485; Ctr-TAT-CPE452-466 vs BDNF-TAT-CPE452-466, *p = 0.0266; Ctr-TAT-CPE452-466 vs Gly+BDNF-TAT-CPE452-466, ***p = 0.0006, n = 4). D, Quantitation of spine-head width in B. Two-way ANOVA with Bonferroni's multiple comparisons test, F(2,18) = 9.212, Ctr-TAT-Con versus BDNF-TAT-Con, ****p < 0.0001; Ctr-TAT-Con versus Gly+BDNF-TAT-Con, ****p < 0.0001; BDNF-TAT-Con versus Gly+BDNF-TAT-Con, #p = 0.0226; Ctr-TAT-CPE452-466 versus BDNF-TAT-CPE452-466, *p = 0.0394; Ctr-TAT-CPE452-466 versus Gly+BDNF-TAT-CPE452-466, *p = 0.0242, n = 4. All the data are presented as mean ± SEM (n ≥ 25 cells for each condition per experiment).