Name: an unpredictable chronic mild stress protocol for instigating depressive symptoms, behavioral changes and negative health outcomes in rodents
Uploaded: 2015-12-02T15:00:00
Description: 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

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...

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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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