Figure 5.

Analysis of the behavioral phenotype of Tag-1^−/−;plp^Tg(rTag-1) compared with the Tag-1^−/− and Tag-1^+/+ mice. A, Acquisition of the hidden version of the MWM. Mean latency ± SEM across the 4 d of the acquisition phase. Note that Tag-1^−/−;plp^Tg(rTag-1) mice reached the hidden platform faster than the Tag-1^−/− mice and with the same latency as Tag-1^+/+ animals. Genotype effect, *p < 0.05; day of training effect, ^###p < 0.001. B, Long term memory probe trial (performed 24 h after the last training trial) of the hidden version of the MWM. BI, Time spent in the target and opposite quadrants during the probe trial. Bar graphs depict mean ± SEM. Note that both Tag-1^−/−;plp^Tg(rTag-1) and Tag-1^+/+ mice showed a preference for the target quadrant. BII, Representative paths followed by Tag-1^−/−;plp^Tg(rTag-1) and Tag-1^−/− mice during the probe trial. T marks the quadrant where the platform was located during training and the arrow the starting position in the probe trial. Genotype × quadrant interaction, ^††p < 0.01; quadrant effect, ^♦♦♦p < 0.05. C, Performance in the novel-object recognition task, expressed as the discrimination index. Bar graphs depict mean ± SEM. Tag-1^−/−;plp^Tg(rTag-1) and Tag-1^+/+ mice spent more time exploring the novel than the familiar object, as expected; in contrast, Tag-1^−/− mice did not show a preference for the novel object (genotype effect, ***p < 0.001). D, Motor coordination as assessed by the rotarod test. DI, Latency to fall across the 3 d of training. Mean latency ± SEM. DII, Latency to fall during the testing phase. Bar graphs depict mean ± SEM. Tag-1^−/−;plp^Tg(rTag-1) and Tag-1^+/+ mice stayed on the rotarod for a longer time before falling off compared with the Tag-1^−/− mice on the second and third days of training as well as during testing at 20 and 32 rpm speed (**p < 0.01; ***p < 0.001). E, Footprint analysis. EI, Overlap width, for both right and left limbs, was significantly smaller in the Tag-1^−/−;plp^Tg(rTag-1) and Tag-1^+/+ mice compared with the Tag-1^−/− mice (***p < 0.001). EII, Stride length, for both right and left limbs; the front and hind stride measurements were significantly larger in the Tag-1^−/−;plp^Tg(rTag-1) and Tag-1^+/+ mice than those in the Tag-1^−/− mice (**p < 0.01; ***p < 0.001). Bars represent mean ± SEM. EIII, Representative photograph of footprints from a Tag-1^−/−;plp^Tg(rTag-1) and a Tag-1^−/− mice animal, indicating the parameters measured: a, Stride length; b, overlap width.