Light/dark transition 01/Nov/2008 RIKENMPP_025_001 test 0 1 testSt test modification

The light/dark transition test assesses anxiety-like behavior in mice. This test is based on the natural behavior of mice to avoid illuminated areas and move to dark areas. Results from this test can be affected by the locomotor activity of the mice in a novel environment. The testing apparatus consists of a light (illuminated) chamber connected to a dark chamber. The period of time that the mouse stays in the light chamber indicates the anxiety level of the mouse.

Testing should be performed by individuals who have been trained and have demonstrated competency in performing the procedures described herein. Any queries, comments or suggestions, relating either to this SOP in general or to a specific problem encountered during procedure should be addressed to the Behavioral Neuroscience Project Leader. Any deviation from this protocol must be reported to the Behavioral Neuroscience Project Leader.

Testing is performed in accordance with the specified safety and hygiene rules.

Although the period of time spent in the light chamber is used as indicator of anxiety levels in mice, immobility induced by fear and anxiety may also increases the amount of time spent in the light chamber. In these cases, the number of transitions between chambers or the distance that the mouse travels markedly decreases; mice should be carefully observed to determine whether freezing behavior is present. Take an extra caution not to stimulate the mouse before starting the experiment. Do not change the cage on the day of the experiment, because this may significantly influence the test result.

A bright environment tends to decrease the spontaneous locomotor activity of mice. Thus, differences in the sensitivities to light of the test subject and control mice must be investigated. The light/dark transition test examines responses to a novel environment. Repeating the test decreases the novelty of the test scene. Because results vary significantly between the first and second tests, the data should always be grouped for analysis based in the test number when the test is repeated. Because rearing conditions (individual rearing or group rearing) and experimental histories may also influence the results, the test and control groups should be raised and examined in a similar manner.

A light chamber (floor: 200 mm in length, 200 mm in width, and 250 mm in height) and a dark chamber (floor: 200 mm in length, 200 mm in width, and 250 mm in height) are connected in the apparatus. The light chamber is made of white vinyl chloride plates and the dark chamber is made of black vinyl chloride plates. The apparatus has a hole 50 in width, 30 mm in height in the middle of the connection between the chambers, which can be opened and closed with a guillotine door. CCD cameras are mounted onto the ceiling. To monitor and record mouse movements during an experiment, a CCD camera, a TV monitor, and a video recorder are used. A CCD camera is mounted above the center of each chamber Illumination is provided by a fluorescent lamp on the ceiling and a 4 W fluorescent lamp mounted above the light chamber.

1000-fold diluted Purelox (6% sodium hypochlorite) solution Paper towel Duster

Transfer a mouse from a rearing room to the testing room 15 minutes before starting an experiment (note 1). (note 1) Take care not to stimulate the mouse before starting the experiment. Do not change the cage on the day of the experiment, because it may influence the test result significantly. Soak the floor cloth in the drug solution and wring it out to wipe the floor and walls of the apparatus clean. Take a mouse by the tail and place it into the dark chamber with the guillotine door closed. The door to the light chamber is opened 30 seconds later. Measure the amount of time before the mouse enters the light chamber, the number of transitions between chambers, the period of time spent in the light chamber, and the total distance traveled by the mouse. Take the mouse out of the apparatus after 10 minutes. Remove any feces with a paper towel and clean the floor (tray) with water.