Name: testing animal anxiety in rats: effects of open arm ledges and closed arm wall transparency in elevated plus maze test
Uploaded: 2018-06-29T12:30:00.000+00:00
Duration: 7 min 54 s
Description: Watch this Scientific Journal Video about Testing Animal Anxiety in Rats: Effects of Open Arm Ledges and Closed Arm Wall Transparency in Elevated Plus Maze Test at JoVE.com

The authors wish to thank Mr. Akihiro Hirano for his assistance in producing the customized apparatus. The authors would like to thank Mr. Kosuke Takahashi and Mr. Shingo Nakajima for their technical assistance. This work was supported by Research on Risk of Chemical Substances, Health and Laboratory Sciences Research Grants, Ministry of Health, Labour and Welfare, Japan (H25-KAGAKU-IPPANN-003) and Research Project Grant A by Institute of Science and Technology Meiji University, Japan.

All experimental procedures described here have been approved by the Institutional Animal Care and Use Committee of Meiji University (IACUC 14-0002(1)). Animals used in the representative results were prepared as follows: Male Sprague-Dawley rats were purchased from a laboratory animal company and housed in groups of 4 animals per standard rat cage (W200 &#215; D410 &#215; H250 mm) for at least one week before the start of the behavioral experiment.&#160;The animal housing room was maintained at standard ambient conditions for light (12:12 light/dark schedule with lights on at 10:00 h), room temperature (25.0 &#177; 0.5 &#176;C), humidity (55 &#177; 10%), and ventilation (10 times/h), and animals had ad libitum access to food (Oriental Yeast Co. Ltd., Tokyo, Japan) and water. The animals were kept in a standard rat cage (W410 x D250 x H200 mm, Toyoriko Co., Ltd., Aichi, Japan) with paper bedding (alpha-dri, LSG Corporatin, Tokyo, Japan).
1. Elevated Plus Maze Test
<ol>
	<li>Set up the elevated plus maze apparatus in a customized container (W1,500 &#215; D1,500 &#215; H2,000 mm) (Figure 1A) with a plus-shaped metal framework 500 mm above the floor to support the run way arms (Figure 1B), lighting in the container ceiling to illuminate the surface of the maze to the required light intensity (Figure 1C), and a digital video camera in the center ceiling to enable live video monitoring of the behavioral tests (Figure 1C).</li>
	<li>Fix the arms (L500 x W100 mm) on the plus-shaped framework, and then fix the square central platform (W100 x D100 mm) at the center of the four arms (Figure 1D - F). 
	NOTE: In our laboratory, we have two types of open arms (L500 x W100 mm) and two types of closed arms (L500 x W100 x H450 mm) (Figure 1D). The closed arms have either transparent or opaque walls (Figure 1D), and the open arms are designed with or without a short ledge (H5 mm, Figure 1E). The square central platform (W100 &#215; D100 mm) is placed at center of the four arms (Figure 1D - F). Thus, the following four combinations of arms can be prepared according to experimental purpose: open arms with ledges + closed arms with transparent walls (Ledges/Transparent), open arms with ledges + closed arms with opaque walls (Ledges/Opaque), open arms without ledges + closed arms with transparent walls (No-Ledges/Transparent), and open arms without ledges + closed arms with opaque walls (No-Ledges/Opaque). The surface of the arm runway is black, to enable better animal tracing by the automated behavior analysis software, as described in&#160;Section 2, Behavioral Analysis.</li>
	<li>Adjust lighting intensity on the surface of the distal end part of each arm and central platform to approximately 100 Lux.</li>
	<li>Before each test, clean the entire apparatus with 70% ethanol solution and wipe with distilled water.</li>
	<li>Click the &#34;record button&#34; on the hard disk recorder to start the digital video camera that will record the rat&#39;s behavior for the video imaging analysis described in Section 2, Behavioral Analysis.</li>
	<li>Place an animal on the central platform facing an open arm and allow free exploration on the apparatus for 5 min.</li>
	<li>Click the &#34;stop button&#34; on the hard disk recorder to finish the recording.</li>
	<li>Count the number of feces and urinations after returning the tested animal to the animal housing room.</li>
	<li>Repeat from step 1.4 until the end of the experiment. 
	NOTE: A dry test run is always carried out before starting each experiment to check that all the experimental settings are correctly set up before any experimental animals are exposed to the experimental conditions. Otherwise, some animals, especially the first animal may experience different environmental conditions (e.g., noises possibly induced by the experimenter during manipulation and/or animal cues possibly left by the previously tested animal). 
	NOTE: The experimenters are near the container when an animal is being tested. Thus, even though the experimenters are not visible the rat may still be able to sense them via smell and/or sound.</li>
</ol>
2. Behavioral Analysis
Note: Behavioral analysis is performed by manual observation and automated analysis software.
<ol>
	<li>Manual observation
	<ol>
		<li>After the animal is placed on the ledge, observe the following: number of entries (an entry onto an arm is defined as any instance when all 4 paws are on the arm), time spent on each arm, and number of stretched-attending postures facing an open arm, while backing off the central platform towards a closed arm.</li>
		<li>Measure duration and&#160;frequency of the behaviors defined above by stopwatch and count for 5 min, starting from when the doors of the container are closed.</li>
	</ol>
	</li>
	<li>Automated analysis
	<ol>
		<li>Using the available software program, record the following: distance traveled, time spent in different positions on open arms (proximal, middle, and distal segments from the central platform), and a minute-by-minute analysis of the time spent on open and closed arms.</li>
		<li>Click the &#34;start button&#34; of the automated analysis software at the same time as the manual observation begins (the recording will stop automatically if recording duration is set). 
		NOTE: The behavioral analysis software used in this study tracks the animal via its contrast with the background field; the animal, which is assigned a fixed size, is identified as the brighter object and the locomotion of its center point can thus be used for animal tracking.</li>
	</ol>
	</li>
</ol>

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The authors have nothing to disclose.

As the number of patients suffering from psychiatric disorders, including anxiety-disorder, increases, it is important to develop cutting-edge studies to improve understanding of the basic mechanism of anxiety. To achieve this, it is also important to optimize the experimental procedures. Therefore, to improve the application of the elevated plus maze test, we have demonstrated the effect of arm features on experimental outcomes using rats.
The elevated plus maze was originally established to test animal anxiety in rodents4, but although the basic structures are usually consistent (e.g., elevated 500 mm above the floor with a plus shape), various arm designs are often used. Originally, the apparatus consisted of open arms without ledges, and closed arms with wooden opaque walls. However, more recently open arms have been developed with ledges to prevent animals falling off the apparatus, and closed arms have also been developed with transparent walls to facilitate observation of behavior on the closed arms. However, there have been no reports that addressed the combined effects of these arm features on the experimental outcomes in the elevated plus maze test. As shown by our results, the presence of open arm ledges and the transparency of the closed arm walls decreased avoidance of open arm exploration in rats (Figure 2), which may decrease the detection sensitivity of the anxiolytic effect of diazepam (Figure 3). The Ledges/Transparent apparatus appeared to encourage greater exploration on the open arms by vehicle treated rats (Figure 3). This reduced behavioral discrimination in open arm exploration activity between vehicle and diazepam treated rats, thus making it more difficult to detect differences in anxiety levels. Therefore, the lower sensitivity of Ledges/Transparent apparatus may mean that more animals would need to be tested to demonstrate significant treatment effects compared with using No-Ledges/opaque apparatus.
In our protocol, the duration and number of entries onto each arm was manually measured by well-trained experimenters. This procedure enables accurate measurement of arm entries, defined as all 4 paws placed on an arm. Although it is true that automated animal tracking systems are available for some behavioral parameters, such as traveling distance, in our experience they cannot always accurately distinguish between entries and non-entries onto arms, especially when animals perform stretched-attending postures near the border between the central platform and an arm. Thus, we recommend using a combination of both manual and automated observation systems, based on their respective strengths for each behavioral parameter.
There are some other protocol differences between laboratories. For example, some researchers place animals on the central platform facing a closed arm13,14, whereas others place the rats facing an open arm15,16. In addition, some researchers test behavior immediately after taking rats from their home-cage, whereas others allow the rats some time to acclimatize to the behavior testing room before starting the test. With respect to former case, in preliminary tests we experienced how the outcomes differed depending on which arm the rat initially faced; there was an increased incidence of entering onto the arm that the rat was placed facing. Also, when the rats were placed facing a closed arm, some animals did not move out of that closed arm after the first entry. In such a case, it is difficult to distinguish whether the rats experience conflict between the open and closed arms or that they merely prefer to be in a closed place without ever recognizing the presence of the open arms. Although in our study we chose to place the rats facing an open arm, to ensure a high incidence of being under conflict, we recommend that further studies be conducted to ensure that the effect of this protocol difference on experimental outcomes is properly investigated.
The measurements of exploration of the distal segment of open arms and minute-by-minute analysis provided extra detailed information about rat anxiety-like behavior. These measurements helped to show the differences in detection sensitivity between the different arm designs. Despite this, reported results of anxiety research using the elevated plus maze test often do not report these types of detailed measurements13,17,18. Therefore, we highly recommend that researchers also report further information about rat exploratory activities, including distal exploration, minute-by-minute analysis, and also stretched-attending posture.
In conclusion, our findings suggest that different types of apparatuses may have their own characteristics. From these tests, we have demonstrated that No-ledges/Opaque apparatus can better detect the effect of drugs potentially having an anxiolytic effect. In contrast, it is conceivable that Ledges/Transparent apparatus may have a similar advantage when testing potential anxiogenic drugs. To date, behavioral tests have been used not only for drug screening, but also for phenotyping assays in mutant animals. Indeed, advanced genome editing techniques allow rapid production of mutant animals. Therefore, it is very important to develop testing procedures with better precision and sensitivity to better detect the variations in behavior. This report demonstrates an improved application of the elevated plus test for animal anxiety research based on the expected functions of the drug or target genes. Thus, we believe that our efforts will help to advance research employing the elevated plus maze.

The number of patients suffering from mood disorders, including anxiety-disorder and depression, is increasing. Although the development of these disorders involves both genetic and environmental factors, the detailed pathogenic mechanisms are not yet fully understood1. Therefore, research needs to focus on uncovering the underlying mechanisms of mood disorders, as well as the development of effective drugs that have fewer side effects. 
Behavioral tests for laboratory animals are useful for investigating brain higher function, including emotion. As animal behavior is highly variable, experimental outcomes often differ between laboratories, even if an identical inbred strain was used2. Thus, researchers also need to understand the basic features of the experimental devices they adopt in order to provide reliable, precise outcomes in the laboratory.
The elevated plus maze test was originally established to examine emotional reactivity in rodents3,4. The entire apparatus is usually located 500 mm above the floor, and consists of two open and two closed arms that make a plus shape. Measurements of arm exploration (including duration and frequency of entries on each arm), distance traveled, and specified behaviors such as stretched-attending posture of subjected animals are recorded during observational periods. By these measures, animal anxiety is estimated as an experimental outcome. 
The elevated plus maze test is used throughout the world, but not all laboratories use the same apparatus design5,6, and these differences may affect the experimental outcomes. For example, differences include the presence or absence of ledges along the open arms and/or the use of transparent or opaque walls for closed arms5,6. The ledges along open arms and the use of transparent walls for closed arms were developed to prevent animals falling off the apparatus7, and to facilitate behavioral observations inside the closed arms, respectively8,9. Although there have been some studies that examined how individual arm structure differences may affect the ability to detect animal anxiety1,2,5,10,11, the combined effects of open (with/without short ledge) and closed (transparent/opaque walls) arm features on animal behavior has not yet been investigated. 
In a recent report, we discussed the effect of these combinations of arm designs on anxiety-like behavior in rats12. In brief, open arm ledges significantly increased anxiety-like behavior in rats, while transparent arms may also have decreased this behavior. Furthermore, we verified higher detection sensitivity of the effect of an anxiolytic drug in a combination of no-ledged open arm + opaque walled closed arm compared with a combination of ledged open arm + transparent walled closed arm. In this report, we will introduce our protocol for the elevated plus maze test, together with discussion of the key results from the previous report. We believe this report will provide useful information for those who have employed or who plan to use the elevated plus maze in their studies.

<table><tbody><tr><td>Customized container (W1500 &amp;times; D1500 &amp;times; H2000 mm)</td><td>NA</td><td>NA</td><td>Handmade by Mr. Akihiro Hirano</td></tr><tr><td>Lighting</td><td>NA</td><td>NA</td><td>Handmade by Mr. Akihiro Hirano</td></tr><tr><td>Elevated plus maze apparatus</td><td>NA</td><td>NA</td><td>Handmade by Mr. Akihiro Hirano</td></tr><tr><td>Digital video camera</td><td>Watec</td><td>WAT-250D2</td><td>Any suitable video camera can be attached to a hard disk recorder for recording tracking profiles.</td></tr><tr><td>Hard disk recorder</td><td>TOSHIBA</td><td>RD-R200</td><td>Any suitable hard disk recorder can be attached to the digital video camera.</td></tr><tr><td>Sprague-Dawley rats</td><td>Charles River Laboratories Japan, Inc.</td><td>NA</td><td>Any suitable rats can be used for your study</td></tr><tr><td>Standard rat cage</td><td>Toyoriko</td><td>TP-105</td><td>Any suitable rat cage be used for your study</td></tr><tr><td>Instrument to measure light intensity</td><td>AS ONE</td><td>1-5818-02</td><td>Any suitable instrument to measure light intensity</td></tr><tr><td>EthoVision XT version 8.0</td><td>Noldus</td><td>NA</td><td>Any suitable software to measure animal behavior</td></tr><tr><td>Diazepam</td><td>Taiyo Pharmaceutical Industry</td><td>1124402A2061</td><td>Any suitable drug can be used for your study</td></tr><tr><td>Tween 80</td><td>Wako Pure Chemical Industries</td><td>9005-65-6</td><td>Any suitable drug can be used for your study</td></tr></tbody></table>

testing animal anxiety in rats: effects of open arm ledges and closed arm wall transparency in elevated plus maze test

The elevated plus maze test is a behavioral test for assessing animal anxiety in rodents. Although this test is widely applied in the field of behavioral science, conflicting outcomes are often provided from different laboratories. To identify reasons for the different outcomes, we previously focused on arm features, which differ between laboratories, most notably the presence/absence of ledges at the sides of open arms and the transparency/opaqueness of closed arm walls. In a previous report, we used a custom designed container to compare rat behavior on different combinations of open and closed arm designs under otherwise identical experimental conditions, and showed that differences in arm features interfere with experimental outcomes. In brief, open arm ledges significantly increased anxiety-like behavior in rats, while transparent arms may also have decreased this behavior. Furthermore, we verified a higher detection sensitivity of the effect of an anxiolytic drug in a combination of no-ledged open arm + opaque walled closed arm compared with a combination of ledged open arm + transparent walled closed arm. In this report, we introduce our protocol for the elevated plus maze test, together with discussion of the key results from the previous report and our experimental experience. We believe this report will provide useful information for researchers who have employed or who plan to use the elevated plus maze in their studies.

In the previous study, we compared the combined effects of open arm ledges and transparency of closed arm walls on the exploratory behaviors on the maze12. Rats significantly spent much less time on open arms without ledges than on open arms with ledges (F[1, 60] = 13.49, P = 0.0005) (Figure 2A). Similar results were also found for the number of entries into open arms (F[1, 60] = 11.17, P &#60; 0.0014)12, suggesting that the presence of ledges increases rat exploratory behavior on open arms. Rats significantly showed less stretched-attending posture on the apparatus that had closed arms with transparent walls than on apparatus that had closed arms with opaque walls (F[1,60]= 4.03, P = 0.0492) (Figure 2B), suggesting that transparent closed arm walls decreased anxiety-like behavior in rats. Rats spent more time on the distal segment of open arms on the apparatus that had transparent closed arm walls than on apparatus with opaque closed arm walls (F[1,60] = 8.00, P = 0.0983) (Figure 2C), suggesting that transparent walls may also decrease rat open arm exploratory behavior. Furthermore, open arm exploration on the distal segment was significantly lower in the No-ledges/Opaque apparatus compared to the Ledges/Transparent apparatus (Figure 2C). Taken together, these results indicate that detection sensitivity for anxiety-like behavior could differ depending on the types of arm design features used, and the No-ledges/Opaque apparatus and Ledges/Transparent apparatus may have a relatively large difference in the detection sensitivity.
To verify differences in detection sensitivity between different types of arm design, a further experiment was performed using the anxiolytic drug diazepam (Figures 3A-D). In brief, the No-Ledges/Opaque apparatus detected the effect of high-dose diazepam treatment on the time spent in the open arms, whereas the Ledges/Transparent apparatus did not (Figure 3A-B). Similar results were also found for the number of entries into open arms12 (data not shown). The lack of any significant effect on the Ledges/Transparent apparatus may have been due to the fact that the basal activity (vehicle treatment) on this apparatus was higher than on the No-Ledges/Opaque apparatus, but that open arm exploration never exceeded 33% of the time at any stage on either apparatus. Therefore, this narrower open arm exploration time range made it more difficult to distinguish the anxiolytic effect of diazepam on the Ledged/Transparent apparatus (Figure 3C-D).
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/56428/56428fig1.jpg" /> 
Figure 1: Custom-designed equipment for elevated plus maze test. Panel (A): Elevated plus maze test container. The apparatus is placed in the black container, and a monitor next to the container projects live movie images recorded during the experiment. Panel (B): Plus maze framework in the container that supports fitted arms. Entire apparatus is located 500 mm above the floor. Panel (C): Ceiling lighting that can be adjusted for intensity. A digital video camera (see arrow) surrounded by&#160;lighting records animal movements. Panel (D): Elevated plus maze arms and central platform that are fitted to framework; from left-to-right, opaque wall closed arm, no-ledge open arm, ledged open arm, central platform, transparent wall closed arm. Panel (E): Close-up view of open arms; from left-to-right, open arm without ledges, open arm with ledges (H5 mm). Panel (F): An example of a constructed maze (Ledges/Transparent apparatus). <a href="https://cloudflare.jove.com/files/ftp_upload/56428/56428fig1large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 2" class="xfigimg" src="/files/ftp_upload/56428/56428fig2.jpg" /> 
Figure 2: Open arm ledges reduce anxiety-like behavior, and transparent walls partially decrease anxiety-like behavior. Male rats underwent the elevated plus maze test with different combinations of arm structures (Ledges/Transparent, Ledges/Opaque, No-ledges/Transparent, and No-ledges/Opaque). Testing order was normalized across the experimental groups (each combination of apparatus type). This procedure normalizes unexpected effects that could have occurred due to the time of day of each test. Panel (A): Time spent on open arms; Panel (B): Number of stretched-attending postures; Panel (C): Time spent in the distal segment of open arms. Solid and dashed lines indicate significant main effects of open and closed arm structures, respectively (Two-way ANOVA, #P &#60; 0.1, * P &#60; 0.05, **P &#60; 0.01, ***P &#60; 0.001). Different letters beside the bars in Panel (C) indicate a significant difference (Bonferroni multiple comparison test, a &#60; b, P &#60; 0.0125). The data were expressed as mean with SEM (n = 16 per experimental group). These figures have been modified from our previous report12. <a href="https://cloudflare.jove.com/files/ftp_upload/56428/56428fig2large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 3" class="xfigimg" src="/files/ftp_upload/56428/56428fig3.jpg" /> 
Figure 3: No-Ledges/Opaque apparatus shows higher detection sensitivity of anxiolytic effect of diazepam. Male rats underwent the elevated plus maze test, with either No-Ledges/Opaque or Ledges/Transparent apparatus, 30 min after being treated with either vehicle (0 mg/kg), low (0.25 mg/kg), or high (0.5 mg/kg) doses of the anxiolytic drug diazepam (intraperitoneal injection). Diazepam solution was dissolved in 0.9% normal saline solution with a surface-activating agent. In this experiment, the testing order of the three drug treatment groups and two types of apparatus design were randomized to account for any effects that may occur due to the time of day of each test. Panels (A &#38; B): Total percent time (5 min) spent on open arms of Ledges/Transparent and No-ledges/Opaque apparatus, respectively. Panels (C &#38; D): Minute-by-minute percent time spent on open arms of Ledges/Transparent and No-ledges/Opaque apparatus, respectively. Different letters beside bars in Panel (B) indicate a significant difference between treatments (Bonferroni multiple comparison test, a &#60; b, P &#60; 0.0167). Solid and dashed lines in Panels (C &#38; D) indicate significant main effects of the time-lapse and diazepam treatments, respectively (repeated measures ANOVA, *P &#60; 0.05, **P &#60; 0.01, ***P &#60; 0.001). The data were expressed as mean with SEM. Numbers in the columns indicate animals that completed the experiment (numbers in parenthesis indicate animals falling off the apparatus). These figures have been modified from our previous report12. <a href="https://cloudflare.jove.com/files/ftp_upload/56428/56428fig3large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>

Watch this Scientific Journal Video about Testing Animal Anxiety in Rats: Effects of Open Arm Ledges and Closed Arm Wall Transparency in Elevated Plus Maze Test at JoVE.com

Testing Animal Anxiety in Rats: Effects of Open Arm Ledges and Closed Arm Wall Transparency in Elevated Plus Maze Test

Rats' anxiety-like behavior tested by the elevated plus maze varies highly depending on the testing environment. Here we show how apparatus settings, especially arm structure, affect behavior on the maze, and we explain a reliable protocol to detect effects of anxiolytic drugs. This report will contribute to anxiety research.

The elevated plus maze test is a behavioral test for assessing animal anxiety in rodents. Although this test is widely applied in the field of behavioral ...

testing-animal-anxiety-rats-effects-open-arm-ledges-closed-arm-wall

Nanyang Technological University

Research

JoVE Journal

Behavior

13.5K Views.  Meiji University. Rats' anxiety-like behavior tested by the elevated plus maze varies highly depending on the testing environment. Here we show how apparatus settings, especially arm structure, affect behavior on the maze, and we explain a reliable protocol to detect effects of anxiolytic drugs. This report will contribute to anxiety research. 

Video: Testing Animal Anxiety in Rats: Effects of Open Arm Ledges and Closed Arm Wall Transparency in Elevated Plus Maze Test

The Successive Alleys Test of Anxiety in Mice and Rats

The plus-maze was derived from the early work of Montgomery. He observed that rats tended to avoid the open arms of a maze, preferring the enclosed ones. Handley, Mithani and File et al. performed the first studies on the plus-maze design we use today, and in 1987 Lister published a design for use with mice. 
Time spent on, and entries into, the open arms are an index of anxiety; the lower these indices, the more anxious the mouse is. Alternatively, a mouse that spends most of its time in the closed arms is classed as anxious. 
One of the problems of the plus-maze is that, while time spent on, and entries into, the open arms is a fairly unambiguous measure of anxiety, time in the central area is more difficult to interpret, although time spent here has been classified as &#x201C;decision making&#x201D;. In many tests central area time is a considerable part of the total test time.
Shepherd et al. produced an ingenious design to eliminate the central area, which they called the &#x201C;zero maze&#x201D;. However, although used by several groups, it has never been as widely adopted as the plus-maze. 
In the present article I describe a modification of the plus-maze design that not only eliminates the central area but also incorporates elements from other anxiety tests, such as the light-dark box and emergence tests. It is a linear series of four alleys, each having increasing anxiogenic properties. It has given similar results to the plus-maze in general. Although it may not be more sensitive than the plus-maze (more data is needed before a firm conclusion can be reached on this point), it provides a useful confirmation of plus-maze results which would be useful when, for example, only a single example of a mutant mouse was available, as, for example, in ENU-based mutagenesis programs.

The plus-maze measures anxiety-like behaviour in rodents. There are two opposite closed and two opposite open arms; anxious rodents avoid the open arms. The central area is neither completely open nor closed, so time spent here is ambiguous and difficult to interpret. Here a modification of the plus-maze protocol eliminating this area is described.

The plus-maze was derived from the early work of Montgomery. He observed that rats tended to avoid the open arms of a maze, preferring the enclosed ones.  ...

Barnes Maze Testing Strategies with Small and Large Rodent Models

Spatial learning and memory of laboratory rodents is often assessed via navigational ability in mazes, most popular of which are the water and dry-land (Barnes) mazes. Improved performance over sessions or trials is thought to reflect learning and memory of the escape cage/platform location. Considered less stressful than water mazes, the Barnes maze is a relatively simple design of a circular platform top with several holes equally spaced around the perimeter edge. All but one of the holes are false-bottomed or blind-ending, while one leads to an escape cage. Mildly aversive stimuli (e.g.&#160;bright overhead lights) provide motivation to locate the escape cage. Latency to locate the escape cage can be measured during the session; however, additional endpoints typically require video recording. From those video recordings, use of automated tracking software can generate a variety of endpoints that are similar to those produced in water mazes (e.g.&#160;distance traveled, velocity/speed, time spent in the correct quadrant, time spent moving/resting, and confirmation of latency). Type of search strategy (i.e.&#160;random, serial, or direct) can be categorized as well. Barnes maze construction and testing methodologies can differ for small rodents, such as mice, and large rodents, such as rats. For example, while extra-maze cues are effective for rats, smaller wild rodents may require intra-maze cues with a visual barrier around the maze. Appropriate stimuli must be identified which motivate the rodent to locate the escape cage. Both Barnes and water mazes can be time consuming as 4-7 test trials are typically required to detect improved learning and memory performance (e.g.&#160;shorter latencies or path lengths to locate the escape platform or cage) and/or differences between experimental groups. Even so, the Barnes maze is a widely employed behavioral assessment measuring spatial navigational abilities and their potential disruption by genetic, neurobehavioral manipulations, or drug/ toxicant exposure.

The dry-land Barnes maze is widely used to measure spatial navigation ability in response to mildly aversive stimuli. Over consecutive days, performance (e.g.&#160;latency to locate escape cage) of control subjects improves, indicative of normal learning and memory. Differences between rats and mice necessitate apparatus and methodology changes that are detailed here.

Spatial learning and memory of laboratory rodents is often assessed via navigational ability in mazes, most popular of which are the water and dry-land ...

Use of the Open Field Maze to Measure Locomotor and Anxiety-like Behavior in Mice

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.

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 ...

Quantifying Cognitive Decrements Caused by Cranial Radiotherapy

With the exception of survival, cognitive impairment stemming from the clinical management of cancer is a major factor dictating therapeutic outcome. For many patients afflicted with CNS and non-CNS malignancies, radiotherapy and chemotherapy offer the best options for disease control. These treatments however come at a cost, and nearly all cancer survivors (~11 million in the US alone as of 2006) incur some risk for developing cognitive dysfunction, with the most severe cases found in patients subjected to cranial radiotherapy (~200,000/yr) for the control of primary and metastatic brain tumors1. Particularly problematic are pediatric cases, whose long-term survival plagued with marked cognitive decrements results in significant socioeconomic burdens2. To date, there are still no satisfactory solutions to this significant clinical problem.
We have addressed this serious health concern using transplanted stem cells to combat radiation-induced cognitive decline in athymic rats subjected to cranial irradiation3. Details of the stereotaxic irradiation and the in vitro culturing and transplantation of human neural stem cells (hNSCs) can be found in our companion paper (Acharya et al., JoVE reference). Following irradiation and transplantation surgery, rats are then assessed for changes in cognition, grafted cell survival and expression of differentiation-specific markers 1 and 4-months after irradiation. To critically evaluate the success or failure of any potential intervention designed to ameliorate radiation-induced cognitive sequelae, a rigorous series of quantitative cognitive tasks must be performed. To accomplish this, we subject our animals to a suite of cognitive testing paradigms including novel place recognition, water maze, elevated plus maze and fear conditioning, in order to quantify hippocampal and non-hippocampal learning and memory. We have demonstrated the utility of these tests for quantifying specific types of cognitive decrements in irradiated animals, and used them to show that animals engrafted with hNSCs exhibit significant improvements in cognitive function3.
The cognitive benefits derived from engrafted human stem cells suggest that similar strategies may one day provide much needed clinical recourse to cancer survivors suffering from impaired cognition. Accordingly, we have provided written and visual documentation of the critical steps used in our cognitive testing paradigms to facilitate the translation of our promising results into the clinic.

Cognitive impairment resulting from the radiotherapeutic management of brain tumors represents a clinically intractable condition that adversely impacts quality of life. The capability to critically evaluate potential interventions for ameliorating radiation-induced cognitive decrements ultimately depends on the capability to undertake rigorous quantitative assessments of cognition.

With the exception of survival, cognitive impairment stemming from the clinical management of cancer is a major factor dictating therapeutic outcome. For ...

Medicine

A New Method for Inducing a Depression-Like Behavior in Rats

Contagious depression is a phenomenon that is yet to be fully recognized and this stems from insufficient material on the subject. At the moment, there is no existing format for studying the mechanism of action, prevention, containment, and treatment of contagious depression. The purpose of this study, therefore, was to establish the first animal model of contagious depression.
Healthy rats can contract depressive behaviors if exposed to depressed rats. Depression is induced in rats by subjecting them to several manipulations of chronic unpredictable stress (CUS) over 5 weeks, as described in the protocol. A successful sucrose preference test confirmed the development of depression in the rats. The CUS-exposed rats were then caged with na&#239;ve rats from the contagion group (1 na&#239;ve rat/2 depressed rats in a cage) for an additional 5 weeks. 30 social groups were created from the combination of CUS-exposed rats and na&#239;ve rats.
This proposed depression-contagion protocol in animals consists mainly of cohabiting CUS-exposed and healthy rats for 5 weeks. To ensure that this method works, a series of tests are carried out - first, the sucrose preference test upon inducing depression to rats, then, the sucrose preference test, alongside the open field and forced-swim tests at the end of the cohabitation period. Throughout the experiment, rats are given tags and are always returned to their cages after each test.
A few limitations to this method are the weak differences recorded between the experimental and control groups in the sucrose preference test and the irreversible traumatic outcome of the forced swim test. These may be worth considering for suitability before any future application of the protocol. Nonetheless, following the experiment, na&#239;ve rats developed contagion depression after 5 weeks of sharing the same cage with the CUS-exposed rats.

This protocol describes a new model by which healthy rats could contract depression over a given time periodthrough contagion by exposure to chronic unpredictable stressed (CUS) rats.

Contagious depression is a phenomenon that is yet to be fully recognized and this stems from insufficient material on the subject. At the moment, there is ...

Elevated Plus Maze for Mice

Although the mouse genome is now completely sequenced, the functions of most of the genes expressed in the brain are not known. The influence of a given gene on a specific behavior can be determined by behavioral analysis of mutant mice. If a target gene is expressed in the brain, behavioral phenotype of the mutant mice could elucidate the genetic mechanism of normal behaviors. The elevated plus maze test is one of the most widely used tests for measuring anxiety-like behavior. The test is based on the natural aversion of mice for open and elevated areas, as well as on their natural spontaneous exploratory behavior in novel environments. The apparatus consists of open arms and closed arms, crossed in the middle perpendicularly to each other, and a center area. Mice are given access to all of the arms and are allowed to move freely between them. The number of entries into the open arms and the time spent in the open arms are used as indices of open space-induced anxiety in mice. Unfortunately, the procedural differences that exist between laboratories make it difficult to duplicate and compare results among laboratories. Here, we present a detailed movie demonstrating our protocol for the elevated plus maze test. In our laboratory, we have assessed more than 90 strains of mutant mice using the protocol shown in the movie. These data will be disclosed as a part of a public database that we are now constructing.
Visualization of the protocol will promote better understanding of the details of the entire experimental procedure, allowing for standardization of the protocols used in different laboratories and comparisons of the behavioral phenotypes of various strains of mutant mice assessed using this test. 


The elevated plus maze test is one of the most widely used tests for measuring anxiety-like behavior in mice. Here, we present a movie showing the detailed procedures for conducting the test.

Although the mouse genome is now completely sequenced, the functions of most of the genes expressed in the brain are not known. The influence of a given ...

Biology

Elevated Plus Maze Test Combined with Video Tracking Software to Investigate the Anxiolytic Effect of Exogenous Ketogenic Supplements

The overall goal of this study is to describe the methodology of the elevated plus maze (EPM) test in combination with a video tracking software. The purpose of the method is to document the effect of various potential anxiolytic treatments on laboratory rodent models. The EPM test is based on the rodents&#39; proclivity toward protected, enclosed dark spaces and unconditioned fear of open spaces and heights, and their innate intense motivation to explore novel environments. The EPM test is a widely used behavioral test for investigating the anxiolytic or anxiogenic responses of rodents given drugs that are known to affect behavior. Observation demonstrating a decreased proportion of time spent on closed arms, an increased proportion of time spent on open arms, a reduced number of entries to closed arms, and an elevated number of entries to open arms measured by the EPM test may reflect reduced anxiety levels. Using this method, the effect of exogenous ketone supplements on anxiety-related behavior is tested in Sprague Dawley (SPD) rats. Exogenous ketone supplements are chronically fed to the rats for 83 days or subchronically and acutely orally gavaged, daily for 7 days, before conducting the EPM test. Behavioral data collection is performed using the SMART video tracking system by a blinded observer at the end of the treatments. The main findings indicate that the EPM test is an effective method to detect the ketone supplement-induced anxiolytic effect and can be considered a sensitive measure to assess changes in anxiety behavior associated with drug- or metabolic-based therapies.

Here, we present a protocol to investigate changes in the anxiety level of rodent animal models. The elevated plus maze (EPM) test, used together with a video tracking software, provides a reliable method to document the effect of various potential anxiolytic treatments in preclinical laboratory scenarios.

The overall goal of this study is to describe the methodology of the elevated plus maze (EPM) test in combination with a video tracking software. The ...

Optogenetic Manipulation of Neuronal Activity to Modulate Behavior in Freely Moving Mice

Optogenetic modulation of neuronal circuits in freely moving mice affects acute and long-term behavior. This method is able to perform manipulations of single neurons and region-specific transmitter release, up to whole neuronal circuitries in the central nervous system, and allows the direct measurement of behavioral outcomes. Neurons express optogenetic tools via an injection of viral vectors carrying the DNA of choice, such as Channelrhodopsin2 (ChR2). Light is brought into specific brain regions via chronic optical implants that terminate directly above the target region. After two weeks of recovery and proper tool-expression, mice can be repeatedly used for behavioral tests with optogenetic stimulation of the neurons of interest.
Optogenetic modulation has a high temporal and spatial resolution that can be accomplished with high cell specificity, compared to the commonly used methods such as chemical or electrical stimulation. The light does not harm neuronal tissue and can therefore be used for long-term experiments as well as for multiple behavioral experiments in one mouse. The possibilities of optogenetic tools are nearly unlimited and enable the activation or silencing of whole neurons, or even the manipulation of a specific receptor type by light.
The results of such behavioral experiments with integrated optogenetic stimulation directly visualizes changes in behavior caused by the manipulation. The behavior of the same animal without light stimulation as a baseline is a good control for induced changes. This allows a detailed overview of neuronal types or neurotransmitter systems involved in specific behaviors, such as anxiety. The plasticity of neuronal networks can also be investigated in great detail through long-term stimulation or behavioral observations after optical stimulation. Optogenetics will help to enlighten neuronal signaling in several kinds of neurological diseases.

With optogenetic manipulation of specific neuronal populations or brain regions, behavior can be modified with high temporal and spatial resolution in freely moving animals. By using different optogenetic tools in combination with chronically implanted optical fibers, a variety of neuronal modulations and behavioral testing can be performed.

Optogenetic modulation of neuronal circuits in freely moving mice affects acute and long-term behavior. This method is able to perform manipulations of ...

Validating a Murine Model of Angelman Syndrome Using Behavioral Tests

Behavioral Characterization of an Angelman Syndrome Mouse Model

This manuscript describes a battery of behavioral tests available to characterize Angelman syndrome (AS)-like phenotypes in an established murine model of AS. We use the rotarod learning paradigm, detailed gait analysis, and nest building test to detect and characterize animal motor impairments. We test animal emotionality in the open field and elevated plus maze tests, as well as the affect in the tail suspension test. When AS mice are tested in the open field test, the results should be interpreted with care, since motor dysfunctions influence mouse behavior in the maze and alter activity scores.
The reproducibility and effectiveness of the presented behavioral tests has already been validated in several independent Uba3a mouse lines with different knockout variants, establishing this set of tests as an excellent validation tool in AS research. Models with the relevant construct and face validity will warrant further investigations to elucidate the pathophysiology of the disease and grant the development of causal treatments.

Author Spotlight: A Battery of Highly Reproducible Behavioral Tests to Validate an Angelman Syndrome Murine Model 

This manuscript presents a set of highly reproducible behavioral tests to validate an Angelman syndrome mouse model.

This manuscript describes a battery of behavioral tests available to characterize Angelman syndrome (AS)-like phenotypes in an established murine model of ...

Social Isolation Model: A Noninvasive Rodent Model of Stress and Anxiety

Anxiety disorders are one of the leading causes of disability in the United States (US). Current treatments are not always effective and less than 50% of patients achieve full remission. A critical step in developing a novel anxiolytic is to develop and utilize an animal model, such as mice, to study pathological changes and test drug target(s), efficacy, and safety. Current approaches include genetic manipulation, chronic administration of anxiety-inducing molecules, or the administration of environmental stress. These methods, however, may not realistically reflect anxiety induced throughout daily life. This protocol describes a novel anxiety model, which mimics the intentional or unintentional patterns of social isolation in modern life. The social isolation-induced anxiety model minimizes perceived distractions and invasiveness and utilizes wild type C57BL/6 mice. In this protocol, 6- to 8-week-old mice (male and female) are singly housed in opaque cages to visually block the external environment, such as neighboring mice, for 4 weeks. No environmental enrichments (such as toys) are provided, bedding material is reduced by 50%, any treatment of drug is administered as an agar form, and the exposure/handling of the mice is minimized. Socially isolated mice generated using this protocol exhibit greater anxiety-like behavior, aggression,&#160;as well as decreased cognition.

Presented here is a social isolation (SI)-induced anxiety mouse model that utilizes wild type C56BL/6J mice to induce stress and anxiety-like behavior with minimal handling and no invasive procedures. This model reflects modern life patterns of social isolation and is ideal for studying anxiety and related disorders.

Anxiety disorders are one of the leading causes of disability in the United States (US). Current treatments are not always effective and less than 50% of ...