Study of Anxiety & Depression

Anxiety is the most common and most studied psychiatric field in humans. Anxiety is characteristic of situations that pose either real or imaginary threats to the organism and, as a result, induces changes in behavior. Experimental tests of anxiety in animal models were developed to facilitate the discovery of the genetic and neurobiological substrates of anxiety and test putative anxiolytic drugs.

The methods to assess anxiety-related behaviors in laboratory rodents are commonly divided in two categories: unconditioned (ethological) and conditioned tests.

• Unconditioned tests are usually based on conflicts between exploratory approach/avoidance natural tendencies (open field test, plus maze test, zero maze test, black and white box test, holeboard test, social exploration).
• Conditioned tests are based on the change of responses controlled by conditioning procedures (Aron test, Vogel test, Geiler-Seifter test, acoustic startle, fear-potentiated startle, fear-conditioning, two-way avoidance, learned helplessness, and others.)

Depression, characterized by disturbances in mood, sleep, appetite, energy, motivation, hedonic capacity and thinking is amongst the most prevalent forms of mental illness.

Some behavioral tests in laboratory animals have been shown to be very effective to evaluate depressive symptoms and are classically used to predict the antidepressant effect of new medications. They also provide potentially useful models in which to study neurobiological and genetic mechanisms underlying depressive behavioral changes. These paradigms have strong predictive validity and behavioral responses are reliable and robust within and across laboratories.

• Forced swimming test and tail suspension test are classical paradigms used to evaluate behavioral despair.
• Hopelessness, reported as a common trait of depression in humans, is mimicked in rodents by the paradigm of learned helplessness.
• Finally, anhedonia is classically reflected by a decrease of sweet solution consumption by depressed rodents.