Anxiety rodent behavioral tests

Most rodent behavioral tests of anxiety take advantage of natural conflicts that are faced by rodents that is, rodents are naturally driven to explore a novel environment but also innately to avoid novel environments. These tests are typically referred to as state or normal anxiety tests in order to emphasize that these tests put animals into a one-time stressful situation where natural reactions... 

First, anxiety is not a unitary phenomenon, as it includes innate (trait) anxiety, which is considered to be an enduring feature of an individual, and situation-evoked or experience-related (state) anxiety. Since tests for anxiety in rodents are always restricted to the evaluation of situation-evoked behavior, it might be difficult to investigate trait anxiety in animals. However, the two phenomena are not separable from each other, as individuals with a high trait-anxiety often will show an increased tendency to also display high state anxiety. Thus, the term anxiety will be used without an a priori assumption of trait or state anxiety. 

Among the most frequently used paradigms are tests for unconditioned anxiety that are thought to be indicative for human generahzed anxiety symptoms (Crawley 1999). In these tests, rodents usually are confronted with a novel environment or stimulus, and behavioral patterns related to anxiety (see Sect. 2.1.1) are measured. In the following, the most commonly used tests for unconditioned behavior will be briefly described. 

The behavior of tacl mice was also analyzed in several animal models of anxiety. The open-field test is a widely used tool for behavioral research, but less specific for the evaluation of the anxiety state of the animal, because it is a summation of the spontaneous motor and the exploratory activities, and only the latter is influenced by the anxiety level (Choleris et al. 2001). Under aversive environmental conditions (high level of illumination) the animals activity is strongly affected by the emotional state, while less aversive situations (familiar, dimly lit environment) are useful to assess the general motor activity of mice. Because rodents avoid open areas, the activity of mice in the central part of the open-field arena is inversely correlated to the anxiety level. Tad mice spent only 6.5% of their total activity in the central part, which represented 11% of the total field, indicating that they avoided this aversive area, hi contrast, tacl mice spent 13.6% of their activity in the central area (Bilkei-Gorzo et al. 2002). The increased central activity of the tad mice indicates that the test situation was anxiogenic for tad animals, but less so for the knockout mice. 

Kalueff, A. V., Keisala, T., Minasyan, A., Kumar, S. R., LaPorte, J. L., et al. (2008) The regular and light-dark Suok tests of anxiety and sensorimotor integration utility for behavioral characterization in laboratory rodents. NatProtoc 3, 129-136. 

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