Figure 1
Long-term low-dose THC treatment increases spine density in old, but not in young mice. (a) Time line of the 2-photon imaging experiment. Representative images of the same dendritic segment at day -1 and day 56 acquired during in vivo imaging from 3- (b) and 18- (c) month-old mice treated with vehicle or THC. Scale bar is 2 µm. Spine density changes in 3- (b) and 18-month-old mice (c). Spine density was normalized to the mean spine density during baseline imaging. Grey box indicates the treatment duration. 3-month-old mice (THC n = 12 ROIs, N = 4 mice; vehicle n = 10 ROIs, N = 4 mice); interaction effect F14,192 = 3.247, p = 0.0001; 18-month-old mice (THC n = 22 ROIs, N = 10 mice; vehicle group n = 17 ROIs, N = 8 mice) treatment effect F1,37 = 13.04, p = 0.0009; interaction effect F14,396 = 5.069, p < 0.0001 (day 25 p = 0.0141; day 35 p = 0.0036; day 42 p = 0.0035; day 48 and 56 p < 0.0001). THC effect in comparison to day -1 (day 35 p = 0.0093, day 42 p = 0.0008, day 49 p = 0.0064, day 56 p = 0.0007); vehicle effect in comparison to day -1 (day 56 p = 0.0322) (not shown on the graph). Error bars indicate mean ± SEM; 2-way ANOVA (Mixed-effects analysis) followed by Sidak’s multiple comparison test; * P < 0.05, ** P < 0.01; *** P < 0.001; **** P < 0.0001. ns. - not significant.
