Figure 2.

Behavioral analysis of rats subjected to brain-derived neurotrophic factor (BDNF) knockdown (KD) in the dorsal dentate gyrus (dDG). Lentiviral vector (LV)-shBDNF (knockdown) or LV-shSCR (control) constructs were injected into the dDG of mature rats. The battery of behavioral tests was initiated 3 weeks after recovery from the surgery and the following parameters were measured: sucrose preference (a), activity in a modified forced swim test (FST) (b), home-cage locomotion (c), exploration of a novel environment (d), latency to reach the platform in the water maze task (e) and percent of time spent at the target quadrant during the probe trial in the water maze task (f). Sucrose preference was assessed over a 10-day period using a 0.2% sucrose solution (t(43)=3.526, P=0.01). A modified FST was videotaped, and activity was scored and analyzed using our locally developed software which involves a computer attached joystick³⁵ (t(38)=2.183, P<0.05). Locomotion was automatically measured over four consecutive nights in the home cage of rats (t(41)=2.855, P<0.01). The total distance traveled and number of rearings were automatically quantified in the test for exploration in a novel environment. The water maze task consisted of five training sessions over 5 days, and a test day 3 days later. A two-way repeated measures analysis of variance (ANOVA) revealed a significant Group X session interaction (F(1,26)=4.835, P<0.05). In the water maze task, the latency to find the platform was significantly lower in control rats than in BDNF KD rats at days 2, 3 and 4 (t(26)>2.115, P<0.05) but not at days 1 and 5. The probe trial was conducted 3 days after the training sessions, and the percentage of time spent at the target quadrant was measured during a 1-min test. The level of a random distribution between quadrants was 25%. Values are mean±s.e.m. (n=20 to 23 per group for all tests except for the water maze in which n=14 per group; ^*P<0.05, ^**P≤0.01).