The elevated plus-maze is the most widely used test to measure fear or anxiety and it is particularly sensitive to anxiety-reducing drugs such as benzodiazepines. This test is useful both because of its relative simplicity and short time as well as for its lack of use of reward or conditioning; this test determines the animal’s unconditioned response to a potentially dangerous environment.
Test specifics: The animal is placed in the center of an elevated 4-arm maze with 2 arms open and 2 enclosed arms. Fear/anxiety associated behavior is determined by counting the number of times the animal enters or stays in open or closed arms as well as the time the animal spends in each arm. High anxiety states are directly related to the degree to which the rodent avoids the open arms of the maze and lack of fear is indicated by the “daring” of the animals to enter open arms repeatedly.
The open-field test is a good complementary test to the Elevated plus maze. Anxiety-prone behavior is measured by determining the exploratory pattern of the mouse. Thigmotaxis, the tendency to remain close the walls is higher in anxious animals and decreases gradually during the first minutes of exploration. Therefore, open-field measurements give information both about initial exploratory pattern and habituation patterns.
Test specifics: The animals is placed in the center of an open-field and their activity and exploratory pattern is tracked from 5- 15 min.
This test is based on the natural tendency of rodents to prefer dark enclosed environments as well as their innate tendency to explore a new environment. It is an anxiety-related test useful to determine limbic system damage and is also a used to test the effectiveness of anxiolitic drugs.
Test specifics: The apparatus contains a light opened portion and enclosed dark portion. Rodents prefer dark spaces but also want to explore new ones. Therefore high levels of anxiety can be measured by increased length of time for the animal to emerge into the lighted portion of the apparatus or the avoidance of the area in general while showing no preference for the dark area of the enclosure suggests low levels of anxiety.
A depressed state can be induced in rodents by putting them in a high stress situation from which they cannot escape. The Forced Swim Test is the most commonly used test to screen for depressive-like behavior and is selectively sensitive to antidepressant treatments as well as genetic manipulations.
Test specifics: The animal is placed in a beaker of water and its activity level is monitored. Latency until and duration of immobility is recorded to create an index of depression-like behavior.
Pre-pulse inhibition is based on a cross-species finding where animals and humans are less sensitive to a stimulus once it has been previously presented. Importantly, this behavior is significantly diminished in schizophrenic patients and among patients with Alzheimer’s disease (AD) and is associated with the decreased capacity of these individuals to filter out irrelevant auditory stimulation, taken to signify various aspects associated with these disorders; namely: high levels of distractibility, inattention, and poor cognitive function. The test is particularly useful to evaluate transgenic models of schizophrenia, and Attention Deficit Disorder and potential antipsychotic drugs and potential pharmacological treatments in some AD models. Accoustic startle reactivity is a measure related to anxiety.
Test specifics: The rodent is placed in a small chamber and exposed to a brief pulse of noise (pre-pulse) prior to a second more intense pulse. The reflexive startle response is measured in both trials. The initial response to startle measures the startle reactivity to an acoustic stimulus.
The purpose of this test is to measure territorial aggression in rodents. It is a general measure of aggression.
Test specifics: A naive intruder mouse is placed in the home-cage of a “resident” mouse and latency of attack, aggressive postures and number of attacks are recorded during a 5 min trial.
The purpose of these series of observations is to determine maternal aptitude in rodent mothers.
Test specifics: A series of observations (nest building, pup grooming, pup feeding, huddling etc) are carried out during several days 24 hrs after the birth of the litter. The pup retrieval test involved moving the pups to the opposite end of the cage and timing how long the mother takes to bring them back to their nest.