Defensive withdrawal tests

Rodents do not like to be out in the middle of a large open space. This makes sense, because going into open spaces increases the likelihood that the rodent will be spotted by a predator. Scientists can use the natural desire rodents have to avoid open spaces as a measure of how anxious a rat or a mouse is. In the defensive withdrawal test, rats or mice are placed in a bright open space that has an enclosed dark box off to one side. The amount of time that the rodent spends inside the box compared with the amount of time the rodent spends outside is thought to be a measure of anxiety. This test has been shown to be fairly sensitive to drugs. 

Bhatnagar S, Nowak N, Babich L, Bok L. Deletion of the 5-HT3 receptor differentially affects behavior of males and females in the Porsolt forced swim and defensive withdrawal tests. Behav Brain Res 2004 153(2) 527-535. 

---