Anxiety-like behavior is measured in rodents by quantifying passive avoidance behavior in low-threat situations in which perceived danger is diffuse and uncertain (PMID: 33005134). These situations for a rodent include open spaces and brightly lit spaces. One common trigger for passive avoidance behavior in rodents is the center space of an open field. Similarly, the Elevated Plus Maze measures an animal’s passive avoidance of the open arms. In contrast, light and open space is leveraged together in the Light/Dark Box task, and a decrease in time in the light side of the box has been used to indicate passive avoidance behavior, rather than relying on avoidance of the open space alone.
In contrast to the passive avoidance of anxiety-like measures, fear responses, which have a component of anxiety, are active avoidance behaviors quantified in situations where a threat is imminent and well-defined (PMID: 33005134). Thus, the fear conditioning task is used to evaluate active avoidance and associative memory by quantifying freezing behavior in response to a shock paired with a novel auditory cue and spatial context.
The elevated plus maze (EPM) leverages rodents’ innate inclination to stay close to walls and not to venture out to open spaces (passive avoidance/approach behavior). The EPM apparatus is a cross-shaped maze; two arms of the maze are surrounded by walls while the other arms are open. The EPM apparatus uses beambreaks to measure ambulations, time in arms and the zone, entries into zones and immobility. Less time spent in the open arm or fewer entries as compared to controls suggests increased levels of anxiety-like passive avoidance behavior. Distance traveled is also examined as a measure of exploration in a novel environment.
Our standard protocol is one 5-minute trial. This can be modified to a three-day test (one 5-minute trial per day) to determine if passive avoidance behavior is stable across time. This test is only available for mice and young rats. A larger apparatus is available for larger rats and behavior is tracked via Any-maze software.
EPM measures passive avoidance behavior in a low-threat situation in which perceived danger is diffuse and uncertain. Passive avoidance behavior can also be measured in time spent in the center zone in the Open Field test and in time spent in the light box in the Light/Dark Box task. Together, these tasks inform us of the anxiety-like, passive avoidance features of mouse models.
The contextual and cued fear-conditioning test is one of the most widely used paradigms to assess associative learning and memory. This is a three day task that is followed by a shock sensitivity test. An auditory cue is paired with electric footshock on day 1 (conditioning), then on the following day contextual fear memory (hippocampal-based) is tested by placing the animal in the same context but without auditory cues or footshocks. On day 3, cued fear memory (amygdala-based) is tested by placing the mice in a new context with the auditory cue alone. Percent of time spent freezing is used as a proxy to measure the animal’s fear response.
A shock sensitivity test is conducted after the fear conditioning task to test for potential differences in shock reactivity. Shock sensitivity is assessed to the point of flinch. Available for mice or rats.
The Light/Dark Box test leverages rodents’ innate aversion to brightly illuminated areas and on the spontaneous exploratory behavior of the animals, and is believed to exploit the conflict between the propensity of rodents to explore new environments versus their innate threat aversion. The apparatus consists of a large illuminated compartment and a smaller dark secure compartment. The apparatus uses beambreaks to measure animal movement, location, entries and time spent in each compartment. This task is available for mice only.
The Light/Dark Box test measures passive avoidance in a low-threat situation in which perceived danger is diffuse and uncertain. Passive avoidance behavior can also be measured in time spent in the center zone in the Open Field test and time and entries in the open vs closed arms of the Elevated Plus Maze test. Together, these tasks inform us of the anxiety-like, passive avoidance features of rodent models.
The Open Field test assesses general activity, exploratory behavior and anxiety-like behavior in rodents. It also serves as a control test in order to identify any differences in general activity (hypoactivity, hyperactivity) that may interfere with interpretation of later cognitive, social or emotionality tests that require motoric response. Animals are evaluated over a 1-hr period in a 40 x 40cm enclosure using beambreaks for tracking horizontal and vertical movement. Kinder Scientific Motor Monitor software collects variables such as ambulation (horizontal movement), rearing, location and entries into the center and perimeter zones. The center zone is measured as the inner 50% of the total apparatus and the perimeter zones are located outside of this zone along the walls of the apparatus.
Reduced time spent in and entries to the center zone measures passive avoidance in a low-threat situation in which perceived danger is diffuse and uncertain. Passive avoidance behavior can also be measured in the Elevated Plus Maze and Light/Dark Box test. Together, these tasks inform us of the anxiety-like, passive avoidance features of rodent models.
The Forced Swim Test (FST) is a rodent behavioral paradigm measuring behavioral despair of “depression-like” behavior and learned helplessness. It is a common test used in research of potential antidepressant drugs and in assessing other manipulations expected to affect depression-related behaviors. Mice or rats can be accommodated in this test. Animals are placed in a translucent inescapable beaker or tank of water and behavior is video recorded. Escape related motor behavior is measured as a proxy of learned helplessness. We are currently optimizing this task for automated scoring via Ethovision (Noldus) and will provide the recordings for manual scoring within the investigator’s lab.
The Tail Suspension test is a mouse behavioral paradigm measuring behavioral despair or “depression-like” behavior and learned helplessness. It is a common test used in research of potential antidepressant drugs and in assessing other manipulations expected to affect depression-related behaviors. Mice are suspended by their tails; a thin plastic cylinder is placed around the tailbase to prevent climbing and escape. Freezing behavior is measured as a proxy for learned helplessness. More time spent immobile and a shorter latency to freezing behavior as compared to controls may indicate greater depression-like behavior. ActiMetrics FreezeFrame software is used to record video and Actimetrics Tail Suspension software is used to quantify freezing behavior. Available in mice.