Summary of assays used to measure the anxiety phenotype in rodent models
| Test | Characteristics | Source |
|---|---|---|
| Light/dark box assay | Box apparatus is divided into two sections: the smaller dark “protected” side (minimally lit with black walls), and the larger light ‘unprotected’ side (brightly illuminated with white walls); Relies on the principle of the innate aversion of a rodent to light and exposure to predators as a prey animals; Shorter latency periods entering the light side, and/or longer periods spent here, are interpreted as reduced anxiety-like behaviors; Measures the approach–avoidance behavior | Crawley and Goodwin, 1980; Campos et al., 2013; Lezak et al., 2017 |
| EPM test | Consists of two open, or unenclosed arms opposing two enclosed arms in the shape of a plus sign; Apparatus is elevated several feet from the ground; Animals are placed at the left of the EPM and allowed to explore freely for 5 min; Exposure created by open arms is associated with anxiety-like behavior, such as increased defecation and corticosteroid levels; More time spent in, as well as higher percentage of entries into the open arms of the EPM, are interpreted as reduced anxiety-like indices; Measures approach–avoidance behaviors | Handley and Mithani, 1984; Korte, 2001; Campos et al., 2013; Lezak et al., 2017 |
| Open field test | Consists of an open box divided into layers of rings from the left of the box to the corners; The time spent in the middle where hypothetically the animal is most exposed and vulnerable, is compared with the amount of time spent hugging the safer corners of the box; The number of times ventured towards the left of the box is also recorded; Reduced anxiety is inferred if the animal tends to venture out from peripheral zones, or spend longer periods in the more central zones of the open box; Relies on instinctual fear responses to predators | Lezak et al., 2017 |