Figure 2
Long-term low-dose THC treatment differently alters spine dynamics in old and young mice. (a, f) Turnover ratio—number of lost and gained spines between two consecutive time points divided by the total number of spines in both time points. Percentage of spines that were gained (b, g) and lost (c, h) between two consecutive time points. Percentage of spines that were transient (d, i)—gained in one time point and lost in the consecutive one. (e, j) Survival probability of spines that were gained between day 7 and day 10 (dashed line) of the treatment and all spines present at day 10 (full line). Grey box indicates the treatment duration. (a—e) 3-month-old mice (THC n = 12 ROIs, N = 4 mice; vehicle n = 10 ROIs, N = 4 mice); (a) turnover ratio: time effect F13,179 = 3.718, p < 0.0001; treatment effect F1,20 = 10.93, p = 0.0035 (day 7 p = 0.0017; day 10 p = 0.0033; day 13 p = 0.0014); (b) gained spines: time effect F13,179 = 2.291, p = 0.0080; treatment effect F1,20 = 9.589, p = 0.0057; interaction effect F13,179 = 3.050, p = 0.0004 (day 7 p < 0.0001; day 35 p = 0.0031); (c) lost spines: time effect F13,179 = 3.245, p = 0.0002; treatment effect F1,20 = 10.15, p = 0.0046; interaction effect F13,179 = 2.382, p = 0.0057 (day 10 p = 0.0054; day 13 p = 0.0011); (d) transient spines: time effect F9,117 = 3.715, p = 0.0004; treatment effect F1,20 = 9.299, p = 0.0063; interaction effect F9,117 = 2.812, p = 0.0050 (day 7 p = 0.0002; day 10 p = 0.0237); (e) survival all spines: p = 0.0002; (f–j) 18-month-old mice (THC n = 22 ROIs, N = 10 mice; vehicle group n = 17 ROIs, N = 8 mice); (f) turnover ratio: time effect F13,339 = 4.759, p < 0.0001 ; treatment effect F1,36 = 5.403, p = 0.0259 (day 16 p = 0.0424; day 25 p = 0.0448); (g) gained spines: time effect F13,339 = 3.208, p = 0.0001; (h) lost spines: time effect F13,339 = 2.356, p = 0.0050; treatment effect F1,36 = 7.416, p = 0.0099; (i) transient spines: time effect F9,239 = 1.948, p = 0.0462; treatment effect F1,36 = 8.564, p = 0.0059 (day 10 p = 0.0343); (j) survival gained spines: p < 0.0001; survival all spines: p = 0.0123. Each data point represents one ROI. Error bars indicate mean ± SEM; 2-way ANOVA (Mixed-effects analysis) followed by Sidak’s multiple comparison test; for survival probability analysis (e and j) Kaplan–Meier plot and log rank test (Mantel-Cox test) were used; * P < 0.05, ** P < 0.01; *** P < 0.001; **** P < 0.0001. ns. - not significant.
