Figure 2. Overexpression of BMP4 blocks proliferative and behavioral effects of antidepressant treatment.

(a) Experimental paradigm: Control lentivirus (LV-Control) or a BMP4-overexpressing lentivirus (LV-BMP4) was stereotaxically injected into the dentate gyrus of wild type C57Bl/6 mice. Daily fluoxetine (or vehicle) treatment began on day 5 post-injection. Behavioral performance on the tail suspension test (TST) was performed on day 20 post-injection. BrdU was administered 24 hours prior to sacrifice (Sac) to acutely mark the proliferating cell population and tissue was collected for immunohistochemical analysis on day 21. (b) Immunostaining for DAPI (blue) and BrdU (green) shows that there is an increase in proliferation in the dentate gyrus following fluoxetine treatment in mice infected with LV-Control (Control), but overexpression of BMP4 prevents the fluoxetine-induced increase in BrdU. (c) Quantification of the number of BrdU+ cells per mm³ in the dentate gyrus shows that there is over a two-fold increase in the number of BrdU+ cells following fluoxetine treatment but the effect of fluoxetine is blocked by overexpression of BMP4. n=7–10 per group. (d) Quantification of the number of BrdU+Sox2+ cells per mm³ in the dentate gyrus shows that the number of proliferating progenitor cells is elevated in fluoxetine-treated mice but the effect of fluoxetine is reduced by overexpression of BMP4. n=7–10 per group. (e) Fluoxetine treatment increased the latency to immobility in the TST and the effect of fluoxetine was blocked by overexpression of BMP4. n=7–10 per group. (f) Fluoxetine treatment decreased the total immobility time in the TST and the effect of fluoxetine was blocked by overexpression of BMP4. n=7–10 per group.

Data are presented as mean±SEM. Two-way ANOVA with Bonferroni’s paired comparisons test: *p<0.05, **p<0.01, ***p<0.001. NS=not significant. Scale bar: 50µm