Name: a new method for inducing a depression-like behavior in rats
Uploaded: 2018-02-22T14:30:00
Description: Watch this Scientific Journal Video about A New Method for Inducing a Depression-Like Behavior in Rats at JoVE.com

The authors gratefully acknowledge Dr. R. Bilyar, Resident, Urology Department, Soroka Medical Center, for his help in the laboratory as well as in the video analysis. The support of Shira Ovadia, Director of Animal Resources Unit, is also gratefully acknowledged. Many thanks to A. Alir and to the staff at the Critical Care Unit, Soroka Medical Center for their support and helpful discussions.

The following procedure was conducted according to the recommendations of the Declaration of Helsinki and Tokyo and the Guidelines for the Use of Experimental Animals of the European Community. The experiments were also approved by the Animal Care Committee at the Ben-Gurion University of the Negev.
1. Preparing Rats for the Experimental Procedure
Note: For the experimental procedure, select male Sprague-Dawley rats with no overt pathology, each weighing between 300 a...

According to the results obtained with the application of this protocol, healthy rats, like humans, were negatively affected by depressed rats when housed together over an extended period. The contagiously depressed rats were affected by their already depressed counterparts after five weeks of cohabitation, establishing a distinct animal depression-contagion model for the first time. An earlier study with pigs had also suggested shared emotional statutes between depressed and healthy pigs25.
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Tests carried out in recent times have suggested that psychiatric illnesses could be easily spread to healthy individuals via contagion1. In this case, it is termed social contagion and is spread through affect, attitude, or behavior. This only requires one depressed individual to interact with one or more healthy individuals, thereby facilitating the sharing of emotion. Social relationships are hence a very important component of mood, as they define the transfer of emotions from one individual to the other, by way of mimicry and &#34;emotional contagion&#34;. Time frames for contagion to take effect vary2, inevitably depending on the severity of the emotion and the strength of resistance of the recipient.
The significant consequences of emotional contagion have ensured that studies made in the past mainly focused on the negative aspects. The outcome of negative effects ensured contagion depression received enormous attention, with studies showing that contagion depression increases the likelihood of families and friends of a depressed individual exhibiting depressive behaviors3,4,5,6.
There are both personal and economic reasons for tackling depression. It commonly causes morbidity; and its lifetime incidence is between 13.3 and 17.1% in the United States7. The World Health Organization files show that depression is fourth on the list of global diseases with huge burdens, occurring in people of all genders, ages, social backgrounds, and is equally capable of inflicting poor health, impacting the ability to interact with others8,9,10,11, and causing excess disability12,13. 850,000 lives are estimated to be lost to depressive suicide each year14. Patients are typically prescribed antidepressant medications or advised to undergo cognitive behavioral therapy. These treatmentshelp about 60-80% of patients. However, dealing with the disease still poses a big problem; treatment is not available to all depressed patients. For those who get treatment, some suffer side effects, while others poorly comply with guidelines15. The number of patients resistant to treatment is up to about 40%14. With depression, the economy has frequently suffered in the form of expensive treatment, a decrease in the workforce, and early retirements16. An estimated annual loss of $44 billion in the United States is caused by depression, accounting for almost half of the country&#39;s lost productivity17. Expensive treatment requires careful medical attention, which incurs a variety of increased medical costs and necessitates anticipation of undesirable outcomes, as well as poor response to treatment18.
Having not come across an already proven animal model to study the depression-contagion mechanism, its prevention, and treatment, this hypothetical animal protocol was used for the first time. It suggests that through cohabitation with CUS-exposed rats, healthy rats tend to express depressive behaviors. The main objective of this experiment was to establish a laboratory procedure that highlighted the transfer of depression, via contagion, from CUS-exposed rats to healthy ones. Next, results were evaluated to determine if depression-contagion was limited only to depressive symptoms, or if it was related to other mood disorders, such as anxiety. The ultimate goal of the experiment is to draw closer to better understanding the mechanism of depression-contagion in the race to develop new therapeutic approaches19.

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	<colgroup>
		<col />
		<col />
		<col />
		<col />
	</colgroup>
	<tbody>
		<tr height="40">
			<td height="40" style="height:40px;width:216px;">Rat Cages</td>
			<td style="width:123px;">Techniplast</td>
			<td style="width:344px;">2000P</td>
			<td style="width:167px;">Conventional housing for rodents. Was used for housing rats throughout the experiment</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;">Water</td>
			<td>-</td>
			<td>-</td>
			<td style="width:167px;">Common tap water used througout the experiment at different stages</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;">Purina Chow</td>
			<td>Purina</td>
			<td>5001</td>
			<td style="width:167px;">Rodent laboratory chow given to rats, mice and hamster is a life-cycle nutrition that has been used in biomedical researc for over 5 decades. Provided to rats ad libitum in this experiment</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;">Bottles</td>
			<td>Techniplast</td>
			<td>ACBT0262SU</td>
			<td style="width:167px;">150 ml bottles filled with 100 ml of water and 100 ml 1%(w/v) sucrose solution</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;">Black lusterless perspex box</td>
			<td>-</td>
			<td>-</td>
			<td style="width:167px;">(120 cm &#215; 60 cm &#215; 60 cm), divided into a 25% central zone and the surrounding border zone</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;">Video Camera</td>
			<td>Canon</td>
			<td>-</td>
			<td style="width:167px;">Digital video camera for high definition recording of rat behavior under open field test</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;">Alcohol</td>
			<td>Pharmacy</td>
			<td>-</td>
			<td style="width:167px;">99% pharmaceutical alcohol diluted to 5% and used for lceaning the open field test box before the introduction of each rat</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;">Glass cylinder</td>
			<td>-</td>
			<td>-</td>
			<td style="width:167px;">100 cm tall, 40 cm in diameter, and 40 cm deep cylinder used for carrying out the forced swim test</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;">Paper towels</td>
			<td>Pharmacy</td>
			<td>-</td>
			<td style="width:167px;">Dry towels used for keeping rats dry after immersing them in water</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;">Bold markers</td>
			<td>-</td>
			<td>-</td>
			<td style="width:167px;">Common bold markers used for labeling rats</td>
		</tr>
	</tbody>
</table>

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.

The sucrose preference test: After exposing rats to 5 weeks of CUS for induction of depression, and then subsequently exposing healthy rats to the CUS-exposed rats for a further 5 weeks, both sets of rats displayed depressive-like behaviorsat the end of the experiment (Figure 2). The evidence of this behavior was seen in the reduced preference for sucrose by the depressed rats, after CUS (65 &#177; 2.8%, p &#60; 0.001, Figure 2), when compared t...

Watch this Scientific Journal Video about A New Method for Inducing a Depression-Like Behavior in Rats at JoVE.com

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

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