Spatial learning in ADAM11-deficient mice
To study the functions of ADAM11 in the hippocampus, we examined the spatial learning ability of ADAM11-deficient mice using the Morris Water Maze task [27]. First, mice were trained in a hidden platform task, in which mice searched for a submerged platform to escape from the water. Adam11 (-/-) mice were found to take a significantly longer time to locate the hidden platform than (+/+) and (+/-) mice (Fig. 2A). Nonetheless, the ability of (+/+), (+/-) and (-/-) mice to find the hidden platform improved over test sessions (Fig. 2A). Thus, (+/+), (+/-) and (-/-) mice were able to learn the location of the hidden platform during the course of the trials, although the capacity of (-/-) mice to find the platform was lower than that of (+/+) and (+/-) mice. We further performed a probe test, in which the platform was removed from the pool after completion of the hidden platform task, and the trained mice were allowed to swim freely for 60 sec. The time spent in the target quadrant of (-/-) is significantly lower than that of (+/+) mice (Fig. 2B). Adam11 (+/-) mice appeared to spend a shorter time in the target quadrant, but there was no significant difference between (+/+) and (+/-) mice (Fig. 2B). These results indicate a spatial learning impairment in (-/-) mice. The swimming distance of (+/+), (+/-) and (-/-) mice, however, was similar during the probe trial (Fig. 2C). In the visible platform task, the performance of mice with (+/+), (+/-) and (-/-) genotypes improved during the course of the test sessions, as indicated by a progressive decrease in the latency for locating the platform (Fig. 2D), suggesting that (-/-) mice learn this visible platform task just as well as (+/+) and (+/-) mice. These results also indicated that (-/-) mice have normal visible and motor function and the motivation needed in the water maze task.