Figure 4.

Loss of cholinergic neurons in the medial septal nucleus (MSN) of Thy1-APPL1 mice and accumulation of endosomes in Thy1-APPL1 mice. A, Representative light microscopy images comparing ChAT-immunoreactive neurons in the MSN of non-Tg and Thy1-APPL1 mice at 12–13 months of age. Scale bar, 100 µm. B, Plots of number of ChAT⁺ neurons counted stereologically versus age of mice showing significant difference between the slopes of non-Tg and Thy1-APPL1 mice (F_(1,55) = 6.01, p = 0.017, linear regression). C, Number of ChAT-immunoreactive neurons in the MSN of non-Tg and Thy1-APPL1 mice at the indicated ages (n = 42 for non-Tg and 41 for Thy1-APPL1 mice; quantitative stereology as described in Materials and Methods). D, Representative images of ChAT-immunoreactive neurons at higher magnification in 18-month-old non-Tg and Thy1-APPL1 mice (arrowheads indicate dystrophic neurites). Scale bar, 5 µm. E, Representative z-stacked series fluorescence images of ChAT- (red) and rab5-immunoreactive (green) neuron in the MSN of a non-Tg and Thy1-APPL1 mice at 18 months of age (arrowheads indicating a dystrophic neurite). Scale bar, 5 µm. *p < 0.05, ***p < 0.001, two-tailed, unpaired t test. Data presented as mean ± SEM. F, Representative EM images of 18-month-old mice showing an accumulation of endosomes in cortical dendrites of Thy1-APPL1 mice compared with non-Tg mice (scale bar, 500 nm). G, Quantification of average size and circumference of endosomes in the cortical dendritic area of non-Tg and Thy1-APPL1 mice at the age of 18 months (n = 4 for non-Tg and n = 5 for Thy1-APPL1 mice; 60 cortical section images/mouse, a total of 982 endosomes were counted in Thy1-APPL1mice, with an average of 196 endosomes/mouse counted. 630 total endosomes were counted from non-Tg mice, with averaging 157 endosomes/mouse), *p < 0.05, two-tailed, unpaired t test. Data shown as mean ± SEM.