Dendritic degeneration in frontocentral commissural neurons of APP23 and APP48 mice. a: A type I neuron in an 18 month-old wild type animal exhibits a symmetric dendritic tree with prominent secondary and tertiary branches. b: In contrast, the dendritic tree of a representative type I commissural neuron (I) in a 15-month-old APP23 mouse is degenerated. Most basal dendrites were shrunken and had a reduced caliber (arrows). The degenerated dendrites showed some branches (arrows) that distinguished the degenerated type I neuron (I) from type II neurons without ramifications near the soma (II). c: Such a degeneration of the dendritic tree was not seen in APP48 mice. d-f: Numbers of DiI-traced type I, type II and type III commissural neurons in 15-18-month-old mice. d: APP23 mice at 15 months of age showed a decrease by more than 50% of the type I commissural neurons compared with 18-month-old wild type and APP48 mice. e: There was a significant reduction of type II commissural neurons in APP23 mice at 15 months of age compared with wild type littermates and APP48 mice at 18 months of age. f: Although APP23 mice had higher numbers of type III commissural neurons there was no significant difference from wild type littermates. g-h: No significant differences among the frequencies of DiI-traced type I, type II, and type III commissural neurons were observed at 3 months of age. ** p < 0.01 (Further statistical analysis: Additional file
2). Means and standard errors are depicted in d-i. (Quantitative data from APP23 mice and their respective wild type littermates were previously published in a different context
). Calibration bar in c corresponds to: a-c = 30 μm.