Loss of APP affects morphology of hippocampal CA1 pyramidal neurons. (a) Representative examples of 3D-reconstructed CA1 neurons from WT (left) and APP-KO mice (right). Note the differences in dendritic complexity: arrows indicate reduced complexity of mid-apical dendrites and arrowheads an increase in the number of primary basal dendrites in APP-KO neurons. (b) Total dendritic length in APP-KO neurons was slightly, but not significantly decreased when compared to WT neurons (Student’s t-test, p = 0.07). (c, d) Sholl analysis comparing basal (c) and apical (d) dendrites between WT and APP-KO neurons. (c) In basal dendrites of APP-KO neurons dendritic complexity was increased in regions proximal to the soma (30 μm distance; Repeated measure ANOVA with Bonferroni multiple comparison test, ***p ≤ 0.001). (d) Note that in apical dendrites of APP-KO cells dendritic complexity was highly reduced at 300 μm, 330 μm and 360 μm (Repeated measure ANOVA with Bonferroni multiple comparison test, *p ≤ 0.05, **p ≤ 0.01). (e) Comparison of the number of primary basal dendrites. Note that the number of primary basal dendrites is considerably increased in APP-KO (WT: 5.06 ± 0.37 versus APP-KO: 7.10 ± 0.43; Student’s t-test, ***p ≤ 0.001, WT data same as in Figure 1). (f) Total dendritic complexity was decreased, but did not reach significance likely due to the opposing effects on basal and apical dendrites. (g) Input-output-strength was analyzed in organotypic hippocampal cultures at DIV21-24, which revealed no alterations in basal synaptic transmission between WT and APP-KO mice. (h) Paired-pulse facilitation showed no significant differences between genotypes. (g, h) Student’s t-test, n = number of OHCs analyzed per genotype. (b-f) WT: n = 32 neurons/6 mice, APP-KO: n = 42 neurons/7 mice. All values represent mean ± SEM.