This study was supported by the American Heart Association (IRG 14330015, PRE 16850005, PRE 20380386, EIA 0740129N), and the National Institutes of Health (RR 2865AR; P20 RR 016477).

All procedures described below have been reviewed and approved by the Institutional Animal Care and Use Committee at the West Virginia University Health Sciences Center.
1. Selection of Animal Model&#160;

NOTE: Most commonly used species in the UCMS model include Sprague Dawley, and Wistar rats and the BALB/cJ mouse; other murine models have shown limited efficacy (DBA/2, C57BL/6).&#160; However, careful consideration should be given to the particular mouse or rat strain of choice, as the genetic background and susceptibility to environmental stressors vary widely among species and have been shown to be critical factors affecting the outcomes of the study11,14,15,19.
<ol>
	<li>Use animals of the appropriate age (e.g.,&#160;if the desired endpoint is to be evaluated in a 17-week old rat, then the rats must start the UCMS protocol at ~9 weeks of age) as this protocol takes at least 7-9 weeks to fully induce depressive symptoms.</li>
	<li>Single-house animals undergoing UCMS in IACUC-approved cages and facilities, with food and standard chow available ad libitum (unless otherwise required by specific protocol).</li>
	<li>Take special care to ensure controls are housed in a quiet room with minimal activity to reduce effects of any possible unknown environmental stressors.</li>
</ol>
2. Unpredictable Chronic Mild Stress Protocol&#160;
NOTE: Animals undergoing UCMS are transported daily (&#62;5 days per week) to a clean room used for UCMS manipulations. Animals are exposed to 1 or 2 of the stressors listed below each day. Stressors are performed on a randomized schedule, and each stress is administered for a minimum of 3-4 hr (see Table 1).
<ol>
	<li>Dampen the bedding by pouring 10-20 oz. of clean water into each standard cage. Adjust the amount of water accordingly to the size of the cage in order to fully dampen the bedding but not to cause pooling of water. Reside the animals in damp cage for 3-4 hr.</li>
	<li>Remove bedding from each cage for 3-4 hr, after which animals are transitioned into another stressor requiring an empty cage (shallow bath, cage tilt) or placed into a clean cage with fresh bedding.</li>
	<li>Tilt cages to approximately 45&#176; (without bedding) for 3-4 hr. Cages can be tilted with a sturdy object that will remain in place as the animal moves around in the cage.</li>
	<li>Alter normal 12 hr/12 hr light/dark cycles into successions of 30 min periods lasting for 8 hr. After, return animals to the normal cycle.</li>
	<li>Transfer each animal from its home cage to that of the cage of a neighboring animal that has been removed for 3 hr.</li>
	<li>Remove all bedding from each cage and add water to a depth of ~0.25 inches for mice or ~0.5 inches for rats for approximately 4 hr. Use water that is warmer than RT (~30 &#176;C) to minimize hypothermia potential. Briefly dry animals with a soft towel at the conclusion of the water exposure prior to placement into clean cages.</li>
	<li>Expose animals to predator smells/sounds by adding randomly distributed sample tufts of fur or urine (10-20 ml) from a natural predator species into the cage for 3-4 hr. Alternatively, play growling or predatory noises from natural predator species in close proximity to cages for 3 hr.</li>
	<li>At the end of each daily stress period, place all animals into clean cages and return them to the housing facility.</li>
</ol>
3. Animal Monitoring/Grooming Scores
<ol>
	<li>Inspect each animal daily for the development of wounds or sores that may require veterinary treatment. Animals that develop mild injuries may continue in the UCMS protocol on the consent of the veterinarian.
	<ol>
		<li>Two investigators trained in evaluating coat grooming inspect each animal and assign a weekly coat score on a scale of 0-1. This score is determined by assigning individual scores (0- clean, 1-dirty) to each of 8 body regions- head, neck, dorsal coat, ventral coat, tail, forelimbs, hind limbs, and genital region. The same investigators are to perform this task throughout the UCMS protocol to maintain consistency in assigning coat scores.</li>
		<li>Any animal that experiences a sharp reduction in body weight (i.e., &#62;15%) should be reported to the veterinary staff and must be removed from the protocol.</li>
	</ol>
	</li>
</ol>
4. Behavioral Testing and Outcome Measurements&#160;
NOTE: Several methods of assessment can be used to quantify behavioral changes from the UCMS protocol in rodents.
<ol>
	<li>Cumulative Coat Grooming Score.
	<ol>
		<li>As described above, a weekly coat grooming score is assigned for each animal.</li>
	</ol>
	</li>
	<li>Sucrose Splash Test:
	<ol>
		<li>Place the animal in a clean cage lined with an cotton pad or towel to prevent bedding from adhering to its coat. Spray a 10% sucrose solution onto the head and dorsal coat of each animal and record total grooming behavior for 5 min.</li>
		<li>Grooming activity (defined as cleaning of the fur by licking or scratching) is measured by latency (idle time between the first spray and initiation of grooming) and frequency (number of times grooming a particular body part).</li>
	</ol>
	</li>
	<li>Sucrose Preference Test:
	<ol>
		<li>Habituate animals to drink 1% sucrose solution (w/v) 72 hr before the test and then provide exposure to two bottles (1% sucrose solution versus tap water in different bottles). After habituation, provide animals with ad libitum access to sucrose solution and tap water for 3 hr. After 3&#160;hr record the consumption volumes of sucrose solution and tap water and calculate sucrose preference as: [(sucrose consumption)/(water consumption + sucrose consumption)]&#215;100.</li>
	</ol>
	</li>
	<li>Tail Suspension Test (Mice Only):
	<ol>
		<li>Suspend mice by the tail from a stable rod (20 cm from the floor) using adhesive tape (2 cm from tip of tail). Record immobility time over 5 min. Mice are considered immobile only when they hang passively and completely motionless.</li>
	</ol>
	</li>
	<li>The Forced Swim Test:
	<ol>
		<li>Place animals in a container (~15-20 cm diameter for mice; ~55-60 cm diameter for rats) filled with water at a temperature of 26&#160;&#177;&#160;0.5&#160;&#176;C. Record the latency to the first bout of mobility and the time spent immobile during the 5-min testing period. At the end of a test, place the wet animal in a holding cage on a heating pad (30&#8211;35&#160;&#176;C) with normal bedding covered by an absorbent paper towel until dry.</li>
	</ol>
	</li>
	<li>Elevated Plus Maze:
	<ol>
		<li>Allow each animal to explore the maze freely for 5 min. Record total entries into each arm, and total time spent in each arm, according to a priori criteria20.</li>
	</ol>
	</li>
	<li>Locomotor Activity:
	<ol>
		<li>Record activity levels, defined as overall movement, fine movements, rearing movements, and inactivity, for both acute (30 min) and/or chronic (12 hr) time periods. Do this using the home cage or a novel environment, depending on the individual environment (although consistency should be maintained) in real time by an observer or post-hoc by replaying and analyzing camera footage.</li>
	</ol>
	</li>
</ol>
5. Expansion/Variation of UCMS Protocol
<ol>
	<li>Administer appropriate therapeutic agents or challenges to study their ability to either blunt the development of UCMS-induced outcomes (if initiated early) or to reverse severity of established UCMS-induced outcomes (if initiated late). This is dependent on the individual laboratory or protocol11.</li>
</ol>
6. Final Outcome Assessments
<ol>
	<li>Following the conclusion of UCMS protocols and behavioral testing, utilize animals in subsequent experiments in a manner that addresses the specific hypotheses, aims or goals of the individual laboratory. &#160; 
	NOTE: As examples, this can include cardiovascular, inflammatory or endocrine responses to chronic stress. Alternatively, therapeutic interventions can be introduced at this point to evaluate their effectiveness and mechanistic underpinnings.</li>
</ol>

<ol>
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M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Autonomic+nervous+system,+inflammation+and+preclinical+carotid+atherosclerosis+in+depressed+subjects+with+coronary+risk+factors.">Autonomic nervous system, inflammation and preclinical carotid atherosclerosis in depressed subjects with coronary risk factors.</a> Atherosclerosis. 212 (1), 292-298 (2010).</li><li>Barden, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Implication+of+the+hypothalamic-pituitary-adrenal+axis+in+the+physiopathology+of+depression.">Implication of the hypothalamic-pituitary-adrenal axis in the physiopathology of depression.</a> J Psychiatry Neurosci. 29 (3), 185-193 (2004).</li><li>Bowman, R. E., Beck, K. D., Luine, V. 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F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Towards+translational+rodent+models+of+depression.">Towards translational rodent models of depression.</a> Cell Tissue Res. 354 (1), 141-153 (2013).</li><li>Mineur, Y. S., Belzung, C., Crusio, W. 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C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Depressive+behavior+and+vascular+dysfunction:+a+link+between+clinical+depression+and+vascular+disease.">Depressive behavior and vascular dysfunction: a link between clinical depression and vascular disease.</a> J Appl Physiol. 108 (5), 1041-1051 (2010).</li><li>Stanley, S. C., Brooks, S. D., Butcher, J. T., d'Audiffret, A. C., Frisbee, S. J., Frisbee, J. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Protective+effect+of+sex+on+chronic+stress-+and+depressive+behavior-induced+vascular+dysfunction+in+BALB/cJ+mice.">Protective effect of sex on chronic stress- and depressive behavior-induced vascular dysfunction in BALB/cJ mice.</a> J Appl Physiol. 117 (9), 959-970 (2014).</li><li>Ibarguen-Vargas, Y., Surget, A., Touma, C., Palme, R., Belzung, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Multifaceted+strain-specific+effects+in+a+mouse+model+of+depression+and+of+antidepressant+reversal.">Multifaceted strain-specific effects in a mouse model of depression and of antidepressant reversal.</a> Psychoneuroendocrinology. 33 (10), 1357-1368 (2008).</li><li>Dalla, C., Pitychoutis, P. M., Kokras, N., Papadopoulou-Daifoti, Z. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Sex+differences+in+animal+models+of+depression+and+antidepressant+response.">Sex differences in animal models of depression and antidepressant response.</a> Basic Clin Pharmacol Toxicol. 106 (3), 226-233 (2010).</li><li>Mutlu, O., Gumuslu, E., Ulak, G., Celikyurt, I. K., Kokturk, S., K&#305;r, H. M., Akar, F., Erden, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effects+of+fluoxetine,+tianeptine+and+olanzapine+on+unpredictable+chronic+mild+stress-induced+depression-like+behavior+in+mice.">Effects of fluoxetine, tianeptine and olanzapine on unpredictable chronic mild stress-induced depression-like behavior in mice.</a> Life Sci. 91 (25-26), 1252-1262 (2012).</li><li>Gumuslu, E., Mutlu, O., Sunnetci, D., Ulak, G., Celikyurt, I. K., Cine, N., Akar, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+effects+of+tianeptine,+olanzapine+and+fluoxetine+on+the+cognitive+behaviors+of+unpredictable+chronic+mild+stress-exposed+mice.">The effects of tianeptine, olanzapine and fluoxetine on the cognitive behaviors of unpredictable chronic mild stress-exposed mice.</a> Drug Res (Stuttg). 63 (10), 532-539 (2013).</li><li>Isingrini, E., Belzung, C., Freslon, J. L., Machet, M. C., Camus, V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Fluoxetine+effect+on+aortic+nitric+oxide-dependent+vasorelaxation+in+the+unpredictable+chronic+mild+stress+model+of+depression+in+mice.">Fluoxetine effect on aortic nitric oxide-dependent vasorelaxation in the unpredictable chronic mild stress model of depression in mice.</a> Psychosom Med. 74 (1), 63-72 (2012).</li><li>Ripoll, N., David, D. J., Dailly, E., Hasco&#235;t, M., Bourin, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Antidepressant-like+effects+in+various+mice+strains+in+the+tail+suspension+test.">Antidepressant-like effects in various mice strains in the tail suspension test.</a> Behav Brain Res. 143, 193-200 (2003).</li><li>Komada, M., Takao, K., Miyakawa, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Elevated+plus+maze+for+mice.">Elevated plus maze for mice.</a> J Vis Exp. (22), 1088 (2008).</li><li>Golbidi, S., Frisbee, J. 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The authors have nothing to disclose.

Extensive clinical and epidemiological evidence has indicated that chronic stress is one of the most potent precipitating factors for depression. Repeated exposure to stressors may potentiate individual vulnerability to depression and other neuropsychiatric disorders as a consequence of the psychological and physical demands within the body that accumulate over time. The use of validated preclinical animal models offers a valuable translational tool for studying depression and comorbid diseases. Firstly, an ideal animal ...

Depressive mental illness is a complex neurological disorder that is currently recognized as a leading cause of disability and disease burden worldwide. The NIMH reports that approximately 12% of Americans suffer from clinical depression, with twice as many women affected versus men1. In the US alone, depression accounts for billions of dollars direct healthcare costs and an estimated $193 billion more in indirect costs (lowered earnings and lost productivity)2. Symptoms of depression include anhedonia, changes in weight and sleep cycles, decreased physical activity and personal hygiene, feelings of hopelessness or guilt, and/or reoccurring thoughts of death or suicide. During the last decade, epidemiologic and clinical studies have indicated that depression is an independent risk factor for cardiovascular disease (CVD) morbidity and mortality3, and is predictive of more severe prognosis of cardiovascular pathologies, including atherosclerosis, hypertension, myocardial infarction, and coronary artery disease, regardless of prior history of overt CVD4. Despite the increasing prevalence and adverse public health impact of depression, the etiology and related pathophysiology of this disease is poorly understood and the heterogeneity of the disorder due to various factors (e.g., genetic, biological, and environmental components) has made clinical diagnosis difficult to define.
Evidence indicates that irresolvable psychological stress is a major contributing factor for developing depressive illnesses and may also be a potent pathogenic factor linking depression and CVD, in part due to disruption and dysregulation of the hypothalamic-pituitary-adrenal (HPA) axis5,6. Dysfunction of the HPA axis is a major mechanism that has been linked to the behavioral and physiological changes observed in depression and the development of several CVD risk factors, including dyslipidemia, obesity, and diabetes7. Multiple preclinical models of depression have been developed in attempt to replicate the mechanism of altered HPA axis activity characteristic of clinical depression; such models provide a validated means for investigating the behavioral, neurological, and physiological changes associated with chronic and acute stress in animals. The validity of an animal model of disease is based on the relevance of the etiology and progression of the model design and its ability to recapitulate anatomical, neurophysiological, and behavioral features observed in human disease. In addition, preclinical responses to treatments (such as SSRIs) should yield similar results to those observed in clinical settings.
Several animal models of stress-induced depression are currently utilized in research, such as learned helplessness, early life stress, and social defeat stress. However, each of these models has inherent disadvantages that lessen their translational efficacy8. Within the last decades, the Unpredictable Chronic Mild Stress (UCMS) protocol has emerged as one of the most translationally-relevant models for studying the pathophysiology of depression in rodents9. This model is based on the fundamental concept that chronic exposure to stressors disrupts stress response systems and ultimately leads to the development of depressive disorders. During the UCMS protocol, animals are exposed to a randomized series of mild environmental and social stressors on a daily basis. A crucial factor that enhances the relevance of this model to human situations lies in the high degree of unpredictability and uncontrollability of the stressors, as well as the time at which they are introduced. Additionally, the UCMS protocol uses only mild stressors, instead of relying on early life or aggressive physical stimuli. Over a period of UCMS exposure, depressive behaviors develop and are comparable to clinical symptoms, including decreased responsiveness to rewards (anhedonia), changes in physical activity and investigative behavior (helplessness and despair), deterioration of the coat state and altered sexual activity10. Almost all demonstrable symptoms of depression have been reported using this model, and studies have demonstrated that these behaviors persist for several weeks following the cessation of stress. In addition, these UCMS-induced depressive behaviors can gradually be revered by chronic, but not acute, treatment with particular antidepressants, suggesting similar neurological effects of therapeutic improvement that closely mirrors the clinical action and variable efficacy of these agents in humans11,14-18 . Here, we report a detailed description of the UCMS protocol and describe typical behavioral and vascular outcomes in mice.

<table border="0" cellpadding="0" cellspacing="0">
	<tbody>
		<tr>
			<td>Temporary animal cages with lids</td>
			<td>n/a</td>
			<td>n/a&#160;</td>
			<td>Provided by your animal care facility</td>
		</tr>
		<tr>
			<td>Rodent bedding</td>
			<td>n/a</td>
			<td>n/a&#160;</td>
			<td>Provided by your animal care facility</td>
		</tr>
		<tr>
			<td>Predator fur or urine</td>
			<td>n/a</td>
			<td>n/a&#160;</td>
			<td>Provided by your animal care facility</td>
		</tr>
		<tr>
			<td>Rodent cage drinking bottles</td>
			<td>n/a</td>
			<td>n/a&#160;</td>
			<td>Provided by your animal care facility</td>
		</tr>
		<tr>
			<td>1000 ml graduated cylinder</td>
			<td>variable</td>
			<td>variable</td>
			<td>This is optional.&#160; Any container from which a known quantiity of water can be poured will be appropriate</td>
		</tr>
		<tr>
			<td>Wooden blocks cut from 2x4</td>
			<td>variable</td>
			<td>variable</td>
			<td>8 inch sections are cut to facilitate cage tilt procedures</td>
		</tr>
		<tr>
			<td>Soft paper towels</td>
			<td>n/a</td>
			<td>n/a&#160;</td>
			<td>Provided by your institution</td>
		</tr>
		<tr>
			<td>Small spray bottle&#160;</td>
			<td>Walmart</td>
			<td>n/a&#160;</td>
			<td>100-200 ml volume is sufficient, used for sucrose splash test</td>
		</tr>
		<tr>
			<td>Medium (mice) or large (rats) plastic tubs for swim testing</td>
			<td>Walmart</td>
			<td>variable</td>
			<td>Should be of sufficient depth that the animals cannot touch bottom (e.g., 2 feet)</td>
		</tr>
	</tbody>
</table>

an unpredictable chronic mild stress protocol for instigating depressive symptoms, behavioral changes and negative health outcomes in rodents

Chronic, unresolved stress is a major risk factor for the development of clinical depression. While many preclinical models of stress-induced depression have been reported, the unpredictable chronic mild stress (UCMS) protocol is an established translationally-relevant model for inducing behavioral symptoms commonly associated with clinical depression, such as anhedonia, altered grooming behavior, and learned helplessness in rodents. The UCMS protocol also induces physiological (e.g., hypercortisolemia, hypertension) and neurological (e.g., anhedonia, learned helplessness) changes that are clinically associated with depression. Importantly, UCMS-induced depressive symptoms can be ameliorated through chronic, but not acute, treatment with common SSRIs. As such, the UCMS protocol offers many advantages over acute stress protocols or protocols that utilize more extreme stressors. Our protocol involves randomized, daily exposures to 7 distinct stressors: damp bedding, removal of bedding, cage tilt, alteration of light/dark cycles, social stresses, shallow water bath, and predator sounds/smells. By subjecting rodents 3-4 hr daily to these mild stressors for 8 weeks, we demonstrate both significant behavioral changes and poor health outcomes to the cardiovascular system. This approach allows for in-depth interrogation of the neurological, behavioral, and physiological alterations associated with chronic stress-induced depression, as well as for testing of new potential therapeutic agents or intervention strategies.

An example of the schedule for one week following the UCMS procedure is shown in Table 1. Each week, stressors were randomized to prevent acclamation and to ensure unpredictability of the stress challenge each day.
Measures of Depressive like Behaviors
Following 8 weeks of UCMS, there were significant alterations to both behavioral and physiological outcomes in chronically stressed rodents relative to their non-stressed control strains. Development ...

Watch this Scientific Journal Video about An Unpredictable Chronic Mild Stress Protocol for Instigating Depressive Symptoms, Behavioral Changes and Negative Health Outcomes in Rodents at JoVE.com

An Unpredictable Chronic Mild Stress Protocol for Instigating Depressive Symptoms, Behavioral Changes and Negative Health Outcomes in Rodents

The unpredictable chronic mild stress (UCMS) protocol is a validated method for studying behavioral and physiological changes associated with chronic stress and depressive symptoms. Eight weeks of imposition of the UCMS protocol induces behavioral changes and poor health outcomes in rodents of either gender.

Chronic, unresolved stress is a major risk factor for the development of clinical depression. While many preclinical models of stress-induced depression ...

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Behavior

22.2K Views.  West Virginia University Health Sciences Center. The unpredictable chronic mild stress (UCMS) protocol is a validated method for studying behavioral and physiological changes associated with chronic stress and depressive symptoms. Eight weeks of imposition of the UCMS protocol induces behavioral changes and poor health outcomes in rodents of either gender.

Video: An Unpredictable Chronic Mild Stress Protocol for Instigating Depressive Symptoms, Behavioral Changes and Negative Health Outcomes in Rodents

Using Chronic Social Stress to Model Postpartum Depression in Lactating Rodents

Exposure to chronic stress is a reliable predictor of depressive disorders, and social stress is a common ethologically relevant stressor in both animals and humans. However, many animal models of depression were developed in males and are not applicable or effective in studies of postpartum females. Recent studies have reported significant effects of chronic social stress during lactation, an ethologically relevant and effective stressor, on maternal behavior, growth, and behavioral neuroendocrinology. This manuscript will describe this chronic social stress paradigm using repeated exposure of a lactating dam to a novel male intruder, and the assessment of the behavioral, physiological, and neuroendocrine effects of this model. Chronic social stress (CSS) is a valuable model for studying the effects of stress on the behavior and physiology of the dam as well as her offspring and future generations. The exposure of pups to CSS can also be used as an early life stress that has long term effects on behavior, physiology, and neuroendocrinology.

This article describes the use of chronic resident intruder social stress as an ethologically relevant paradigm to model postpartum depression and anxiety in lactating rodents.

Exposure to chronic stress is a reliable predictor of depressive disorders, and social stress is a common ethologically relevant stressor in both animals ...

Nest Building as an Indicator of Health and Welfare in Laboratory Mice

The minimization and alleviation of suffering has moral and scientific implications. In order to mitigate this negative experience one must be able to identify when an animal is actually in distress. Pain, illness, or distress cannot be managed if unrecognized. Evaluation of pain or illness typically involves the measurement of physiologic and behavioral indicators which are either invasive or not suitable for large scale assessment. The observation of nesting behavior shows promise as the basis of a species appropriate cage-side assessment tool for recognizing distress in mice. Here we demonstrate the utility of nest building behavior in laboratory mice as an ethologically relevant indicator of welfare. The methods presented can be successfully used to identify thermal stressors, aggressive cages, sickness, and pain. Observation of nest building behavior in mouse colonies provides a refinement to health and well-being assessment on a day to day basis.

We demonstrate the utility of nest building behavior in laboratory mice as an indicator of welfare. Nest scoring is a sensitive technique that is altered by temperature, illness, and aggression. The time to integrate into nest test (TINT) is a simple cage-side assessment that can detect postoperative pain.

The minimization and alleviation of  suffering has moral and scientific implications. In order to mitigate this  negative experience one must be able to ...

The Forced Swim Test as a Model of Depressive-like Behavior

The goal of the present protocol is to describe the forced swim test (FST), which is one of the most commonly used assays for the study of depressive-like behavior in rodents. The FST is based on the assumption that when placing an animal in a container filled with water, it will first make efforts to escape but eventually will exhibit immobility that may be considered to reflect a measure of behavioral despair. This test has been extensively used because it involves the exposure of the animals to stress, which was shown to have a role in the tendency for major depression. Additionally, the FST has been shown to share some of the factors that are influenced or altered by depression in humans, including changes in food consumption, sleep abnormalities and drug-withdrawal-induced anhedonia. The main advantages of this procedure are that it is relatively easy to perform and that its results are easily and quickly analyzed. Moreover, its sensitivity to a broad range of antidepressant drugs that makes it a suitable screening test is one of the most important features leading to its high predictive validity. Despite its appeal, this model has a number of disadvantages. First, the issue of chronic augmentation is problematic in this test because in real life patients need to be treated for at least several weeks before they experience any relief from their symptoms. Last, due to the aversiveness of the FST, it is important to take into account possible influences it might have on brain structure/function if brain analyses are to be carried out following this procedure.

This protocol describes the forced swim test, which is used for the study of depressive-like behavior in rodents. This procedure involves placing an animal in a container filled with water that eventually will lead to the exhibition of immobility behavior, which is considered to reflect behavioral despair.

The goal of the present protocol is to describe the forced swim test (FST), which is one of the most commonly used assays for the study of depressive-like ...

The Double-H Maze: A Robust Behavioral Test for Learning and Memory in Rodents

Spatial cognition research in rodents typically employs the use of maze tasks, whose attributes vary from one maze to the next. These tasks vary by their behavioral flexibility and required memory duration, the number of goals and pathways, and also the overall task complexity. A confounding feature in many of these tasks is the lack of control over the strategy employed by the rodents to reach the goal, e.g., allocentric (declarative-like) or egocentric (procedural) based strategies. The double-H maze is a novel water-escape memory task that addresses this issue, by allowing the experimenter to direct the type of strategy learned during the training period. The double-H maze is a transparent device, which consists of a central alleyway with three arms protruding on both sides, along with an escape platform submerged at the extremity of one of these arms.
Rats can be trained using an allocentric strategy by alternating the start position in the maze in an unpredictable manner (see protocol 1; &#167;4.7), thus requiring them to learn the location of the platform based on the available allothetic cues. Alternatively, an egocentric learning strategy (protocol 2; &#167;4.8) can be employed by releasing the rats from the same position during each trial, until they learn the procedural pattern required to reach the goal. This task has been proven to allow for the formation of stable memory traces.
Memory can be probed following the training period in a misleading probe trial, in which the starting position for the rats alternates. Following an egocentric learning paradigm, rats typically resort to an allocentric-based strategy, but only when their initial view on the extra-maze cues differs markedly from their original position. This task is ideally suited to explore the effects of drugs/perturbations on allocentric/egocentric memory performance, as well as the interactions between these two memory systems.

The goal of this protocol is to investigate spatial cognition in rodents. The double-H water maze is a novel test, which is particularly useful to elucidate the different components of learning, consolidation and memory, as well as the interplay of memory systems.

Spatial cognition research in rodents typically employs the use of maze tasks, whose attributes vary from one maze to the next. These tasks vary by their ...

A Mouse Model of Subchronic and Mild Social Defeat Stress for Understanding Stress-induced Behavioral and Physiological Deficits

Stressful life events often increase the incidence of depression in humans. To study the mechanisms of depression, the development of animal models of depression is essential. Because there are several types of depression, various animal models are needed for a deeper understanding of the disorder. Previously, a mouse model of subchronic and mild social defeat stress (sCSDS) using a modified chronic social defeat stress (CSDS) paradigm was established. In the paradigm, to reduce physical injuries from aggressors, the duration of physical contact between the aggressor and a subordinate was reduced compared to in the original CSDS paradigm. sCSDS mice showed increased body weight gain, food intake, and water intake during the stress period, and their social behaviors were suppressed after the stress period. In terms of the face validity of the stress-induced overeating and overdrinking following the increased body weight gain, the sCSDS mice may show some features related to atypical depression in humans. Thus, a mouse model of sCSDS may be useful for studying the pathogenic mechanisms underlying depression. This protocol will help establish the sCSDS mouse model, especially for studying the mechanisms underlying stress-induced weight gain and polydipsia- and hyperphagia-like symptoms.

Here, methods for developing a mouse model of subchronic and mild social defeat stress are described and used to investigate the pathogenic features of depression including hyperphagia- and polydipsia-like symptoms following increased body weight.

Stressful life events often increase the incidence of depression in humans. To study the mechanisms of depression, the development of animal models of ...

Feeding Experimentation Device (FED): Construction and Validation of an Open-source Device for Measuring Food Intake in Rodents

Food intake measurements are essential for many research studies. Here, we provide a detailed description of a novel solution for measuring food intake in mice: the Feeding Experimentation Device (FED). FED is an open-source system that was designed to facilitate flexibility in food intake studies. Due to its compact and battery powered design, FED can be placed within standard home cages or other experimental equipment. Food intake measurements can also be synchronized with other equipment in real-time via FED's transistor-transistor logic (TTL) digital output, or in post-acquisition processing as FED timestamps every event with a real-time clock. When in use, a food pellet sits within FED's food well where it is monitored via an infrared beam. When the pellet is removed by the mouse, FED logs the timestamp onto its internal secure digital (SD) card and dispenses another pellet. FED can run for up to 5 days before it is necessary to charge the battery and refill the pellet hopper, minimizing human interference in data collection. Assembly of FED requires minimal engineering background, and off-the-shelf materials and electronics were prioritized in its construction. We also provide scripts for analysis of food intake and meal patterns. Finally, FED is open-source and all design and construction files are online, to facilitate modifications and improvements by other researchers.

Feeding Experimentation Device FED: Construction and Validation of an Open-source Device for Measuring Food Intake in Rodents

Feeding Experimentation Device (FED) is an open-source device for measuring food intake in mice. FED can also synchronize food intake measurements with other techniques via a real-time digital output. Here, we provide a step-by-step tutorial for the construction, validation, and usage of FED.

Food intake measurements are essential for many research studies. Here, we provide a detailed description of a novel solution for measuring food intake in ...

An Automated T-maze Based Apparatus and Protocol for Analyzing Delay- and Effort-based Decision Making in  Free Moving Rodents

Many neurological and psychiatric patients demonstrate difficulties and/or deficits in decision making. Rodent models are helpful to produce a deeper understanding of the neurobiological causes underlying the decision-making problems. A cost-benefit based T-maze task is used for measuring decision making in which rodents choose between a high reward arm (HRA) and a low reward arm (LRA). There are two paradigms of the T-maze decision-making task, one in which the cost is a time delay and the other in which it is physical effort. Both paradigms require a tedious and labor-intensive management of experimental animals, multiple doors, pellet reward, and arm choice recordings. In the current work, we invented an apparatus based on traditional T-maze with full automation for pellet delivery, door management and choice recordings. This automated setup can be used for the evaluation of both delay- and effort-based decision making in rodents. With the protocol described here, our lab investigated the decision-making phenotypes of multiple genetically modified mice. In the representative data, we showed that the mice with ablated medial habenular showed aversions of both delay and effort and tended to choose the immediate and effortless reward. This protocol helps to decrease the variability caused by experimenter intervention and to enhance experiment efficiency. In addition, chronic silicon probe or microelectrode recording, fiber-optic imaging and/or manipulation of neural activity can be easily applied during the decision-making task using the setup described here.

This article introduces an automated T-maze apparatus that we invented, and a protocol based on this apparatus for analyzing delay-based decision making and effort-based decision making in free moving rodents.

Many neurological and psychiatric patients demonstrate difficulties and/or deficits in decision making. Rodent models are helpful to produce a deeper ...

The Unpredictable Chronic Mild Stress Protocol for Inducing Anhedonia in Mice

Depression is a highly prevalent and debilitating condition, only partially addressed by current pharmacotherapies. The lack of response to treatment by many patients prompts the need to develop new therapeutic alternatives and to better understand the etiology of the disorder. Pre-clinical models with translational merits are rudimentary for this task. Here we present a protocol for the unpredictable chronic mild stress (UCMS) method in mice. In this protocol, adolescent mice are chronically exposed to interchanging unpredictable mild stressors. Resembling the pathogenesis of depression in humans, stress exposure during the sensitive period of mice adolescence instigates a depressive-like phenotype evident in adulthood. UCMS can be used for screenings of antidepressants on the variety of depressive-like behaviors and neuromolecular indices. Among the more prominent tests to assess depressive-like behavior in rodents is the sucrose preference test (SPT), which reflects anhedonia (core symptom of depression). The SPT will also be presented in this protocol. The ability of UCMS to induce anhedonia, instigate long-term behavioral deficits and enable reversal of these deficits via chronic (but not acute) treatment with antidepressants strengthens the protocol&#39;s validity compared to other animal protocols for inducing depressive-like behaviors.

Here we present the unpredictable chronic mild stress protocol in mice. This protocol induces a long-term depressive-like phenotype and enables to assess the efficacy of putative antidepressants in reversing the behavioral and neuromolecular depressive-like deficits.

Depression is a highly prevalent and debilitating condition, only partially addressed by current pharmacotherapies. The lack of response to treatment by ...

Stress-Enhanced Fear Learning, a Robust Rodent Model of Post-Traumatic Stress Disorder

Fear behaviors are important for survival, but disproportionately high levels of fear can increase the vulnerability for developing psychiatric disorders such as post-traumatic stress disorder (PTSD). To understand the biological mechanisms of fear dysregulation in PTSD, it is important to start with a valid animal model of the disorder. This protocol describes the methodology required to conduct stress-enhanced fear learning (SEFL) experiments, a preclinical model of PTSD, in both rats and mice. SEFL was developed to recapitulate critical aspects of PTSD, including long-term sensitization of fear learning caused by an acute stressor. SEFL uses aspects of Pavlovian fear conditioning but produces a distinct and robust sensitized fear response far greater than normal conditional fear responses. The trauma procedure involves placing a rodent in a conditioning chamber and administering 15 unsignaled shocks randomly distributed over 90 minutes (for rat experiments; for mouse experiments, 10 unsignaled shocks randomly distributed over 60 minutes are used). On day 2, rodents are placed in a novel conditioning context where they receive a single shock; then, on day 3 they are placed back in the same context as on day 2 and tested for changes in freezing levels. Rodents that previously received the trauma display enhanced levels of freezing on the test day compared to those that received no shocks on the first day. Thus, with this model, a single highly stressful experience (the trauma) produces extreme fear of the stimuli associated with the traumatic event.

Here we describe the detailed methodology required to conduct stress-enhanced fear learning (SEFL) experiments, a preclinical model of post-traumatic stress disorder, in both rats and mice. The model utilizes aspects of Pavlovian fear conditioning and freezing as an index of enhanced fear in rodents.

Fear behaviors are important for survival, but disproportionately high levels of fear can increase the vulnerability for developing psychiatric disorders ...

Novel Object Recognition and Object Location Behavioral Testing in Mice on a Budget

Ethologically relevant behavioral testing is a critical component of any study that uses mouse models to study the cognitive effects of various physiological or pathological changes. The object location task (OLT) and the novel object recognition task (NORT) are two effective behavioral tasks commonly used to reveal the function and relative health of specific brain regions involved in memory. While both of these tests exploit the inherent preference of mice for the novelty to reveal memory for previously encountered objects, the OLT primarily evaluates spatial learning, which relies heavily on hippocampal activity. The NORT, in contrast, evaluates non-spatial learning of object identity, which relies on multiple brain regions. Both tasks require an open-field-testing arena, objects with equivalent intrinsic value to mice, appropriate environmental cues, and video recording equipment and the software. Commercially available systems, while convenient, can be costly. This manuscript details a simple, cost-effective method for building the arenas and setting up the equipment necessary to perform the OLT and NORT. Furthermore, the manuscript describes an efficient testing protocol that incorporates both OLT and NORT and provides typical methods for data acquisition and analysis, as well as representative results. Successful completion of these tests can provide valuable insight into the memory function of various mouse model systems and appraise the underlying neural regions that support these functions.

Here we provide a protocol which includes comprehensive instructions for the economical establishment of murine object location and novel object recognition behavioral testing, including the design, cost, and construction of required equipment as well as execution of behavioral testing, data collection, and analysis.