Research on anxiety and depression in rodents

Anxiety, fear, and depression are studied in a wide variety of neuroscience domains. Anxiety can be induced by novel environments or open spaces versus more closed ones. That is why most test paradigms are conflict tests based on a natural tendency of rodents to actively explore such a novel or more open environment versus their innate fear of being in this environment. These types of tests are typically used for anxiety-related effects of drugs, compounds such as alcohol, and neurological defects.

EthoVision® XT is the perfect tool to track animal behavior, activity, and movement. Noldus also offers additional equipment to make full automation of your research possible. Our collaboration with Med Associates allows us to offer high quality equipment including open fields, elevated plus maze, elevated zero maze, and a forced swim test apparatus, to create a solution that suits your research.

Anxiety, fear, and depression-like behaviors are studied in rodents using a variety of paradigms in psychopathology, such as

• Open field activity
• Elevated plus maze
• Elevated zero maze
• Forced swim test

A wizard to make your life easier
The latest version of EthoVision XT, version 8, offers a new user guided set-up; a wizard helps you get started by simply choosing your animal, your test, and some other basic settings. It leads you to a template, that you can fine-tune to your specific experiment. This way your experiment will be up and running quickly! EthoVision XT 8 includes a variety of templates, including those for anxiety tests, the plus maze, zero maze, and forced swim test.

Behaviors related to areas of interest
EthoVision XT allows you to specify different zones or points of interest from the video images of your test arena. This allows the program to automatically measure parameters related to these zones. Examples include the latency to the first entrance into the inner zone of an open field or to the open part of a plus or zero maze, and the time spent in these zones. You can investigate thigmotaxis by calculating the percentage of time spent along the walls of the open field.

Automatic detection of behaviors
In addition to center-point tracking, EthoVision XT is able to detect and track the nose point and tail base of mice and rats. This allows for the accurate measurement of animal position, enabling you to discriminate between the animal only poking its nose around the corner or moving its entire body into one of the open arms of an elevated plus maze. It also allows EthoVision XT to automatically detect behaviors such as body elongation – characteristic of the stretch-attend posture that is often considered a response to an environment that incites both fear/anxiousness and curiosity. Another behavior that can be automatically detected is immobility, indicative of freezing. The three variations of mobility – immobile, mobile, and highly mobile – indicate the three most important behaviors in the forced swim test; floating, swimming, and climbing/ escaping. The thresholds for mobility are user-definable, so you can optimize them for your study. One way of fine-tuning these settings to fit your definition of the behavior is by performing a pilot experiment and visualizing the results alongside the video.

 
Extra efficiency
You can program EthoVision XT to automatically start and stop the tracking of your animal, increasing the efficiency of your research. At the start of an elevated plus maze test, the animal is traditionally placed in the central square, facing an open arm. In a zero maze, the animal is often placed in one of the closed segments. Either way, you can program EthoVision XT to automatically start tracking as soon as the animal is detected in this ‘starting zone’. In a forced swim test, mice are often not habituated because some studies show that this influences the test results. Therefore, the first two minutes are seen as the habituation phase of the test and are not included in the results. You can program EthoVision XT to start tracking two minutes after the mouse is detected in the cylinder. You can also program the stopping of tracking; 5 minutes after start, for example.

 
Data integration
Some studies combine behavioral data with physiology. They use telemetry to gather data such as heart and respiration rate, providing additional information on the fear response of the animal. EthoVision XT enables the integration of external data streams alongside tracking data.
translate data into meaningful results Data interpretation is, of course, a crucial step in your research. EthoVision XT provides you with the useful parameters and data selection tools to perform this step, including the time spent in the open arms or quadrants in a plus or zero maze or the amount of time spent climbing and the latency to floating in a forced swim test. It also reveals how these numbers change over consecutive trials, or how these compare between different treatment groups. It helps you translate data into meaningful results. The ratio between time spent in the open versus the closed arms can be taken as a measure of anxiousness, as is the amount of time spent immobile in an open field test. The latency to floating in a forced swim test is indicative of depressive-like behavior.