Figure 5

Anxiety-like behavior and behavioral pattern separation impairment produced by LPS treatment and GSK-3β overexpression. (a) Anxiety-like behavior was evaluated in the elevated plus maze paradigm. Animals were subjected to a 5-min single trial. Data are presented as the total time spent standing or walking on the open arms. LPS significantly reduced the time the animals spent on open arms, thus indicating increased anxiety-like behavior, which was still observable 2 weeks after LPS withdrawal. GSK-3-OE mice also spent less time on open arms than WT mice. These differences were abolished by doxycycline treatment (which switched off the transgene expression). Although ibuprofen completely reversed the alterations produced by LPS treatment, it did not cause any change in GSK-3-OE mice. This observation points to a prominent role for GSK-3β in anxiety-like behavior. (b–c) To evaluate their behavioral pattern separation capacity, animals were tested in the novel location preference test. The trial was performed on three consecutive days. Each day animals were subjected to a single 10-min trial (see schematic diagram). The first day, they were placed inside the arena and were allowed to explore it for habituation. During the second day (sample phase), two identical objects were placed symmetrically in the central part of the arena. On the third day (test phase), one of the objects (novel located object) was moved to a peripheral position, whereas the other one remained unaltered. Index memory (time exploring novel located object/time exploring novel+unaltered object) is shown in the graphs. In addition, the total number of explorations is indicated. The LPS dose administered did not significantly alter the general exploratory behavior (c). However, it produced a drastic and permanent reduction of memory index (b). GSK-3-OE mice also showed a reduced memory index, which was fully restored after Doxycycline treatment. Although ibuprofen completely reversed the alterations produced by LPS treatment, it did not cause any change in GSK-3-OE mice. This finding supports the previously demonstrated prominent role of GSK-3β in hippocampal-dependent learning. (*, 0.01<P<0.05) (**, 0.001<P<0.01) (***P<0.001). LPS, lipopolysaccharide; PBS, phosphate-buffered saline; WT, wild type.