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A protocol is provided to use an Open Field Maze to access general locomotor activity, anxiety and emotionality in a laboratory mouse model.
Animal models have proven to be invaluable to researchers trying to answer questions regarding the mechanisms of behavior. The Open Field Maze is one of the most commonly used platforms to measure behaviors in animal models. It is a fast and relatively easy test that provides a variety of behavioral information ranging from general ambulatory ability to data regarding the emotionality of the subject animal. As it relates to rodent models, the procedure allows the study of different strains of mice or rats both laboratory bred and wild-captured. The technique also readily lends itself to the investigation of different pharmacological compounds for anxiolytic or anxiogenic effects. Here, a protocol for use of the open field maze to describe mouse behaviors is detailed and a simple analysis of general locomotor ability and anxiety-related emotional behaviors between two strains of C57BL/6 mice is performed. Briefly, using the described protocol we show Wild Type mice exhibited significantly less anxiety related behaviors than did age-matched Knock Out mice while both strains exhibited similar ambulatory ability.
The Open Field Maze (OFM) was initially developed in 1934 as a test to measure emotionality in rodents1. It has attained the status of being one of the most widely used measures of behavior in animal psychology2. It provides an easy and fairly rapid assessment of well-defined behaviors requiring no training to the test subject and little to no specialized training for the human administering the test. These attributes have led to wide-spread use of the open field maze in research extended to other animal species such as calves, pigs, rabbits, primates, honeybees and lobsters3. Part of its popularity arises from the fact that the psychological and physiological concepts underlying the tests are generally straight-forward and well understood. For example, it has been postulated that evolutionary forces have selected for a common response in animals such that most species display anxiety-mediated fear or flight responses to specific stimuli. Rodents for example, show distinct aversions to large, brightly lit, open and unknown environments4. We can assume they have been phylogenetically conditioned to see these types of environments as dangerous. All of these features are incorporated in the open field maze and form the basis of its use in behavioral paradigm testing.
An open field maze consists of a wall-enclosed area that is of sufficient height to prevent the subject from escaping. Typical maze shapes are circular or square with an area large enough, based on the size of the subject tested, to elicit a feeling of openness in the center of the maze. A number of variables can be scored in the open field maze with most parameters involving differing types of motor activity2. Ambulation is the most common behavior studied but others such as latency or rearing can also be measured. Most often, rodent behavior is analyzed in a bare maze. However, the addition of objects, either one or many to the maze floor, adds the ability to see how the subject interacts with novel additional stimuli2. Relevant parameters when objects are presented are typically the number of approaches to an object or in some cases, preference or aversion for one object over another.
Many behavioral tests of anxiety are based on the subject animal’s body activity and locomotion5. Interpreting behavioral tests for emotionality while separating non-emotional confounding factors, such as motor activity, has been the subject of intense debate6,7. As the OFM was originally described, two measures of emotionality can be deduced, locomotor activity and fecal boli deposits or defecation1. However, these two measures have been shown in some studies to be unrelated supporting the conclusion that emotionality in rodents is multidimensional5. Regardless, discrepancies in the literature regarding these measures and emotionality or anxiety in mouse models may be attributed to differences in analysis criteria or differences in testing procedures. Studies have conclusively linked results from OFM analysis with other measures of anxiety when comparing mouse models8.
NOTE: All procedures performed here were submitted to and approved by IACUC (Office of Research Compliance) and were conducted following NIH guidelines. Mice used in the behavioral testing paradigm were naive and not used for other tests. The C57BL/6 Wild Type and Knock Out mice used in this protocol have been described previously9 and the data presented here are from that manuscript.
1. Preparation of the Testing Room and Open Field Apparatus
2. Preparing the Software to Measure Activity
3. Administration of the Open Field Test
NOTE: The software package used in this protocol allows the tracking of up to 16 individual mice at one time. For ease of completion and as mentioned above, the protocol discussed here is for a single mouse using a single quadrant of the OFM. For the equipment in use for this protocol, a maximum of 4 individual mice could be tracked using each quadrant of the maze. If utilizing a multi-enclosure maze, after placing the first subject mouse in its defined quadrant, place the remaining mice into their respective maze quadrant for tracking analysis. For the purposes of this protocol, further instruction will be specific to a single quadrant of the maze.
4. Measurement and Analysis of Behavior During Testing Procedure
NOTE: For measurement, three aspects of open field behavior are readily characterized using this protocol (see discussion). A brief instruction on how to access these measurements in the video tracking software follows.
The average number of individuals per strain of mice tested in most cases is approximately 20 to generate sufficient statistical relevance. However, this number can be in the range of 8-30 depending on mouse availability. Depending on the measurement or comparisons required, it is also favorable to use age-matched subjects.
The first and arguably most important specific parameter to measure in the Open Field Maze is total ambulatory distance. While the unit of measure is irrelevant for compari...
The Open Field Maze is one of the most widely used platforms in animal behavioral studies. A number of important conventional and ethological parameters2,4 can be collected and analyzed during the performance of the OFM. These data allow the researcher to measure behaviors ranging from overall locomotor activity to anxiety-related emotional behaviors8. However, use of OFM is not without its shortcomings. One confounding issue is the wide range of static variables that can be manipulated during any t...
The authors have nothing to disclose.
This work was supported by The National Institute of Health (NIH-2RO1NS033661) and by the Alabama Agricultural Experiment Station (HATCH ALA021-1-09017).
Name | Company | Catalog Number | Comments |
Multi Unit Open Field Test | San Diego Instruments, Inc. | White 7001-0354 | Any single or multi unit open field maze can be used |
SMART DT Tracking Software | PanLab/Harvard Apparatus | 76-0695 | Any tracking software can be utilized with this protocol |
Sony 990x Video Camera Recorder | Sony | CCD-TRV328 | Any suitable video camera can be attached to computer for recording tracking profiles. |
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