Novel object recognition test

NORT was performed to evaluate cognition, especially recognition memory in the mice³¹. During the habituation phase, each mouse was allowed to explore the square box (40 × 40 × 40 cm) freely for 5 min. During the familiarization phase, the mice were placed into the box, which contained two identical objects (A + A), and were allowed to explore for 5 min. During the test phase, each mouse was returned to the box with the two objects, where one object was changed into a novel object (A + B), and mice were allowed to explore for 5 min. During both the familiarization and the test phases, the time spent (%) in close-proximity exploration of each object was measured and recorded automatically. At the end of each test, the apparatus and the objects were cleaned with 70% ethanol. The habituation phase was performed immediately prior to surgery, the familiarization phase was performed at day 4 postsurgery, and the test trial was performed at day 5 postsurgery. The discrimination index was evaluated as: (time taken to explore novel object (B)) / (time taken to explore familiar and novel objects (A + B)) × 100, to reflect cognitive ability.