Article Figures & Data
Figures
- Figure 1.
Timeline of experimental procedures. BDNF expression was altered at the dDG of adult (A) and young (B) rats (OE and KD). Then, rats were subjected to 4 weeks of CMS or left undisturbed. Then, behavioral measures were initiated and included sucrose preference (SP), home-cage locomotion (HCl), exploration of a novel environment, and an FST. After the behavioral measurements and 3 d of habituation, blood samples were drawn twice for CORT measurements: before and immediately after acute stress. Seven days later, rats were killed, and brains were removed for BDNF analysis.
- Figure 2.
Validation of LV infection and of BDNF overexpression. A, BDNF protein expression was measured in vitro in the medium of HEK293T cell line. Cells were infected with either LV-expressing GFP alone (LV–GFP) or LV that additionally expressed the coding axon of the rat BDNF gene (LV–BDNF). Secreted BDNF levels were measured in an HEK293T cell medium 48 h after infection and normalized per 106 cell number. Data are presented as percentages of BDNF secreted from non-infected control cells. B, In vivo measurements of BDNF expression in the dorsal hippocampus of adult rats microinjected with LV–GFP or with LV–BDNF into their dDG or in control non-injected adult rats (no infection). Levels of BDNF were measured using sandwich ELISA and are presented as percentages of BDNF extracted from the non-infected control group. Values are mean ± SEM (*p < 0.05, ***p < 0.001). C, Representative micrographs of the dDG of young rats injected with LV–GFP are presented. The selection of coordinates for microinjections was based on preliminary surgeries in young rats and inspection of the infected area under the microscope. The infected region and spread were detected using GFP (right). Cell nuclei were visualized using Hoechst (left). Scale bar, 200 μm. Validation of BDNF KD has been detailed by Taliaz et al. (2010), and BDNF alterations are presented in Figures 3E and 4E.
- Figure 3.
Behavioral effects of CMS and altered hippocampal BDNF expression in adult rats. LV–BDNF (OE) or LV–GFP (control) was injected into the dDG of adult rats, and their behavioral response to 4 weeks of CMS was evaluated according to the timeline detailed in Figure 1. Sucrose preference was assessed over a 9 d period using a 0.2% sucrose solution (A). Distance traveled by the rats was automatically quantified in a 10 min exploration test that was conducted in a novel environment (B), and home-cage locomotion was automatically assessed over 4 d (D). Finally, the activity of the rats in the FST was scored and analyzed automatically (C). After the behavioral analysis, BDNF protein expression was measured in the dDG injected with LV–GFP or LV–BDNF (E). Values are mean ± SEM (*p < 0.05, ***p < 0.001, relative to the control group, which was infected with the control LV and not subjected to CMS).
- Figure 4.
Behavioral effects of CMS and altered hippocampal BDNF expression in young rats. LV–shBDNF (KD) or LV–shSCR (control) was injected into the dDG of young rats, and their behavioral response to 4 weeks of CMS was evaluated (as detailed in Fig. 1). The young rats were further divided to CMS resilient and nonresilient groups (see Materials and Methods). The behavioral measurements include sucrose preference (A), distance traveled at a novel environment (B), activity at the forced swim test (C), and home-cage locomotion (D). In addition, BDNF protein expression was measured in the dDG of young rats injected with LV–GFP or LV–BDNF (E). Values are mean ± SEM (*p < 0.05, **p < 0.01, relative to the control group, which was infected with the control LV and not subjected to CMS).
- Figure 5.
Corticosterone plasma levels of young and adult rats at baseline and after acute stress. Two blood samples were taken from young and adult rats that were subjected to the various BDNF and CMS manipulations. The first blood sample was taken when no stress was induced (Baseline), and the second was taken after the induction of acute stress (Stress). A and B show the effect of BDNF KD on CORT levels in young and adult rats before and after the acute stress, respectively. C and D show the effect of CMS and BDNF KD on CORT levels in young rats. E and F show the effect of CMS and BDNF OE on CORT levels in adult rats. Values are mean ± SEM (*p < 0.05, **p < 0.01).
- Figure 6.
Effects of surgery and CMS on behavior and dDG BDNF levels in young rats. We tested whether the surgeries augmented the behavioral effects of CMS in young rats and altered dDG BDNF expression levels. Sham surgeries were or were not performed before initiation of the CMS procedure. Then, sucrose preference (A) and home-cage locomotion (B) were measured. In addition, the effect of CMS or surgery on dDG BDNF expression was measured (C). Values are presented as mean ± SEM (*p < 0.05).
