Animals, anxiety, and anxiety disorders: How to measure anxiety in rodents and why.

Measurement of anxiety is desirable for the benefit of drug development and understanding the brain function and mental well-being. Animal models offer the advantages of detailed neurobiological analysis, experimental manipulation of specific components in the brain circuits that underlie psychopathology, and the possibility of screening novel drugs with clinical potential. A large variety of animal models of anxiety and screening tests of anxiolytics is currently in use. While their value in advancing the knowledge and predicting therapeutic success of drugs is unquestionable, the expectations have grown much higher, and the frustration over absence of novel successful drug concepts is rising. It is argued that the multitude of factors that can interfere with animal behaviour in anxiety tests, and the complexity of neurobiology of the various anxiety disorders, present high demands on validation of each anxiety test within each specific laboratory condition. Anxiety models should be explicitly related to a theoretical paradigm on underlying neurobiology, because there is a diversity in concepts, and validation of the model and the selection of behavioural readouts is critically dependent on the neurobiological model. Environmental conditions during the model production and anxiety testing need more attention, including the less considered factors such as ultrasounds. More attention is required to the differences in anxiety neurobiology between males and females, and inter-individual differences in coping strategies.