Anxiety

Anxiety is "a future-oriented mood state in which one is ready or prepared to attempt to cope with upcoming negative events" (Barlow and David 2002*), suggesting that it is a distinction between future vs. present dangers that divides anxiety and fear. Anxiety is considered to be a normal reaction to stress that can also help in dealing with difficult situations by providing stimulation to cope with them. When anxiety becomes excessive, it may fall under the classification of an anxiety disorder.

Most of the anxiety tests in the laboratory animals measure stress-induced anxiety or state anxiety with environment as the dominant factor. While the genetic component could be analysed by estimating anxiety under familiar conditions, therefore minimizing influence of stress, this type of anxiety is referred to as trait anxiety, and can be measured as a response to a novel object within the home cage. Elevated plus maze and light-dark chamber are two commonly used tests to measure state anxiety in mice, which are sensitive to pharmacological and genetic interventions.

*Barlow, David H. "Unraveling the mysteries of anxiety and its disorders from the perspective of emotion theory". American Psychologist, 2002: 1247-1263.

Elevated Zero Maze

Procedure

Each mouse is placed onto an open arm of the maze. During a 5 minute observation period, the amount of time spent in the closed/open arm, number of head dips, and number of risk assessments is automatically scored by Ethovision video tracking system.

This task measures the conflict between two natural tendencies of mice. One is to avoid open and elevated narrow spaces and the other one is to explore novel environments.

Equipment

Light-Dark Test

Procedure

The light dark test is used to evaluate the relative anxiety status of mice.

The light dark paradigm in mice is based on a conflict between the innate aversion to brightly illuminated areas and the spontaneous exploratory activity. If given a choice between a large brightly compartment versus a small dark compartment, mice spontaneously prefer the dark. Anxiolytics increase the total duration of time spent there, whereas anxiogenic compounds are observed to work in the opposite way.

One compartment of the chamber is brightly illuminated (400 lux), whereas the other part is dark (5 lux). Mice are placed into the dark side and the door is opened automatically 10 seconds afterwards. The door is used so that the mice do not enter the light chamber immediately after the release with their motivation to escape from experimenter, hence the latency to enter the light chamber may serve as an index of anxiety-like behaviour. Mice are allowed to move freely between the two chambers with door open for 10 minutes. The distance traveled in each compartment, the total number of transitions, the time spent in the each compartment, and the latency to enter the light compartment are recorded.