Figure 7.

Exploratory, anxiety-related behaviors and spatial memory is not affected in absence of NGF-TrkA signaling in young adult or intermediate-aged animals. A, B, Exploratory behaviors were evaluated in the open field test. No significant differences in the time spent in locomotion (Loc), rearing (Rear), grooming (Groom), or in contact with the object (Contact) were observed between Trka^NesCre and age-matched control mice. C, D, Anxiety levels of young and old Trka^NesCre mice were similar to those shown by their age-matched controls as revealed by the time spent in the open arm of an elevated plus maze. E–H, Spatial memory of Trka^NesCre mutant and control mice was evaluated in the invisible version of Morris water maze and the four-baited-arm radial maze at 3–4 months (3–4M) and 11 months (11M) of age. No significant differences were observed between the Trka^NesCre mutant and control mice in the latencies to reach the hidden platform in the Morris water maze during the acquisition phase (6 trials/d for 3 consecutive days) at either stage analyzed (3–4 months, F_(1,18) = 0.99, p > 0.05; 11 months, F_(1,20) = 0.51, p > 0.05; E, F). Reversal learning (6 trials/d for 2 consecutive days) in the Morris water maze was evaluated after the acquisition phase by moving the hidden platform in a new position. No significant differences in the latencies to reach the hidden platform were observed between Trka^NesCre and age-matched control mice (3–4 months, F_(1,18) = 0.19, p > 0.05; 11 months, F_(1,19) = 0.53, p > 0.05). G, H, Learning performance in a four-baited version of the eight-arm radial maze task, expressed as percentage of reference and working memory errors. No significant differences between Trka^NesCre and control mice were observed at 3–4 months (reference memory, F_(1,26) = 0.04, p > 0.05; working memory, F_(1,26) = 0.18, p > 0.05) or 11 months (reference memory, F_(1,25) = 1.8, p > 0.05; working memory, F_(1,25) = 0.51, p > 0.05) of age.