The authors would like to thank Thomas Grace for constructing Y-mazes, barriers, and social defeat cages. The authors would like to thank Jay Lee, Karina Stech, and Prachi Srivastava for assistance with data collection. This work was funded by NIMH Grant R01 MH112861 (BAS).

<ol>
	<li>Kessler, R. C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Lifetime+and+12-month+prevalence+of+DSM-III-R+psychiatric+disorders+in+the+United+States.+Results+from+the+National+Comorbidity+Survey.">Lifetime and 12-month prevalence of DSM-III-R psychiatric disorders in the United States. Results from the National Comorbidity Survey.</a> Arch Gen Psychiatry. 51 (1), 8-19 (1994).</li><li>Breslau, N., Davis, G. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Chronic+stress+and+major+depression.">Chronic stress and major depression.</a> Archives of General Psychiatry. 43 (4), 309-314 (1986).</li><li>Willner, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Chronic+mild+stress+(CMS)+revisited:+consistency+and+behavioural-neurobiological+concordance+in+the+effects+of+CMS.">Chronic mild stress (CMS) revisited: consistency and behavioural-neurobiological concordance in the effects of CMS.</a> Neuropsychobiology. 52 (2), 90-110 (2005).</li><li>Monleon, S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Attenuation+of+sucrose+consumption+in+mice+by+chronic+mild+stress+and+its+restoration+by+imipramine.">Attenuation of sucrose consumption in mice by chronic mild stress and its restoration by imipramine.</a> Psychopharmacology (Berl). 117 (4), 453-457 (1995).</li><li>Willner, P., Towell, A., Sampson, D., Sophokleous, S., Muscat, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Reduction+of+sucrose+preference+by+chronic+unpredictable+mild+stress,+and+its+restoration+by+a+tricyclic+antidepressant.">Reduction of sucrose preference by chronic unpredictable mild stress, and its restoration by a tricyclic antidepressant.</a> Psychopharmacology (Berl). 93 (3), 358-364 (1987).</li><li>Berlin, I., Givry-Steiner, L., Lecrubier, Y., Puech, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Measures+of+anhedonia+and+hedonic+responses+to+sucrose+in+depressive+and+schizophrenic+patients+in+comparison+with+healthy+subjects.">Measures of anhedonia and hedonic responses to sucrose in depressive and schizophrenic patients in comparison with healthy subjects.</a> European psychiatry: the journal of the Association of European Psychiatrists. 13 (6), 303-309 (1998).</li><li>Fawcett, J., Clark, D. C., Scheftner, W. A., Gibbons, R. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Assessing+Anhedonia+in+Psychiatric+Patients:+The+Pleasure+Scale.">Assessing Anhedonia in Psychiatric Patients: The Pleasure Scale.</a> Archives of General Psychiatry. 40 (1), 79-84 (1983).</li><li>Pardo, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Adenosine+A2A+receptor+antagonism+and+genetic+deletion+attenuate+the+effects+of+dopamine+D2+antagonism+on+effort-based+decision+making+in+mice.">Adenosine A2A receptor antagonism and genetic deletion attenuate the effects of dopamine D2 antagonism on effort-based decision making in mice.</a> Neuropharmacology. 62 (5-6), 2068-2077 (2012).</li><li>Salamone, J. D., Cousins, M. S., Bucher, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Anhedonia+or+anergia?+Effects+of+haloperidol+and+nucleus+accumbens+dopamine+depletion+on+instrumental+response+selection+in+a+T-maze+cost/benefit+procedure.">Anhedonia or anergia? Effects of haloperidol and nucleus accumbens dopamine depletion on instrumental response selection in a T-maze cost/benefit procedure.</a> Behav Brain Res. 65 (2), 221-229 (1994).</li><li>Dienes, K. A., Hazel, N. A., Hammen, C. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cortisol+secretion+in+depressed,+and+at-risk+adults.">Cortisol secretion in depressed, and at-risk adults.</a> Psychoneuroendocrinology. 38 (6), 927-940 (2013).</li><li>Gotlib, I. H., Joormann, J., Minor, K. L., Hallmayer, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=HPA+axis+reactivity:+a+mechanism+underlying+the+associations+among+5-HTTLPR,+stress,+and+depression.">HPA axis reactivity: a mechanism underlying the associations among 5-HTTLPR, stress, and depression.</a> Biol Psychiatry. 63 (9), 847-851 (2008).</li><li>Knorr, U., Vinberg, M., Kessing, L. V., Wetterslev, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Salivary+cortisol+in+depressed+patients+versus+control+persons:+a+systematic+review+and+meta-analysis.">Salivary cortisol in depressed patients versus control persons: a systematic review and meta-analysis.</a> Psychoneuroendocrinology. 35 (9), 1275-1286 (2010).</li><li>Joels, M., Karst, H., Sarabdjitsingh, R. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+stressed+brain+of+humans+and+rodents.">The stressed brain of humans and rodents.</a> Acta Physiol (Oxf). 223 (2), 13066 (2018).</li><li>Samuels, B. A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Modeling+treatment-resistant+depression.">Modeling treatment-resistant depression.</a> Neuropharmacology. 61 (3), 408-413 (2011).</li><li>David, D. J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Neurogenesis-dependent+and-independent+effects+of+fluoxetine+in+an+animal+model+of+anxiety/depression.">Neurogenesis-dependent and-independent effects of fluoxetine in an animal model of anxiety/depression.</a> Neuron. 62 (4), 479-493 (2009).</li><li>Dieterich, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Chronic+corticosterone+administration+induces+negative+valence+and+impairs+positive+valence+behaviors+in+mice.">Chronic corticosterone administration induces negative valence and impairs positive valence behaviors in mice.</a> Translational psychiatry. 9 (1), 1-13 (2019).</li><li>Gourley, S. L., Taylor, J. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Recapitulation+and+reversal+of+a+persistent+depression-like+syndrome+in+rodents.">Recapitulation and reversal of a persistent depression-like syndrome in rodents.</a> Current Protocols in Neuroscience. 49 (1), 31-39 (2009).</li><li>Gourley, S. L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Regionally+specific+regulation+of+ERK+MAP+kinase+in+a+model+of+antidepressant-sensitive+chronic+depression.">Regionally specific regulation of ERK MAP kinase in a model of antidepressant-sensitive chronic depression.</a> Biol Psychiatry. 63 (4), 353-359 (2008).</li><li>Gourley, S. L., Wu, F. J., Taylor, J. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Corticosterone+regulates+pERK1/2+map+kinase+in+a+chronic+depression+model.">Corticosterone regulates pERK1/2 map kinase in a chronic depression model.</a> Annals of the New York Academy of Sciences. 1148 (1), 509-514 (2008).</li><li>Mekiri, M., Gardier, A. M., David, D. J., Guilloux, J. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Chronic+corticosterone+administration+effects+on+behavioral+emotionality+in+female+c57bl6+mice.">Chronic corticosterone administration effects on behavioral emotionality in female c57bl6 mice.</a> Experimental and clinical psychopharmacology. 25 (2), 94 (2017).</li><li>Dieterich, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Chronic+corticosterone+shifts+effort-related+choice+behavior+in+male+mice.">Chronic corticosterone shifts effort-related choice behavior in male mice.</a> Psychopharmacology (Berl). , (2020).</li><li>Shafiei, N., Gray, M., Viau, V., Floresco, S. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Acute+Stress+Induces+Selective+Alterations+in+Cost/Benefit+Decision-Making.">Acute Stress Induces Selective Alterations in Cost/Benefit Decision-Making.</a> Neuropsychopharmacology. 37 (10), 2194-2209 (2012).</li><li>Treadway, M. T., Buckholtz, J. W., Schwartzman, A. N., Lambert, W. E., Zald, D. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Worth+the+'EEfRT'?+The+effort+expenditure+for+rewards+task+as+an+objective+measure+of+motivation+and+anhedonia.">Worth the 'EEfRT'? The effort expenditure for rewards task as an objective measure of motivation and anhedonia.</a> PLoS One. 4 (8), (2009).</li><li>Golden, S. A., Covington, H. E., Berton, O., Russo, S. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=p.+A+standardized+protocol+for+repeated+social+defeat+stress+in+mice.">p. A standardized protocol for repeated social defeat stress in mice.</a> Nature protocols. 6 (8), 1183 (2011).</li><li>Yohn, S. E., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+VMAT-2+inhibitor+tetrabenazine+alters+effort-related+decision+making+as+measured+by+the+T-maze+barrier+choice+task:+reversal+with+the+adenosine+A2A+antagonist+MSX-3+and+the+catecholamine+uptake+blocker+bupropion.">The VMAT-2 inhibitor tetrabenazine alters effort-related decision making as measured by the T-maze barrier choice task: reversal with the adenosine A2A antagonist MSX-3 and the catecholamine uptake blocker bupropion.</a> Psychopharmacology (Berl). 232 (7), 1313-1323 (2015).</li><li>Harris, A. Z., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+novel+method+for+chronic+social+defeat+stress+in+female+mice.">A novel method for chronic social defeat stress in female mice.</a> Neuropsychopharmacology. 43 (6), 1276 (2018).</li><li>Takahashi, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Establishment+of+a+repeated+social+defeat+stress+model+in+female+mice.">Establishment of a repeated social defeat stress model in female mice.</a> Scientific Reports. 7 (1), 1-12 (2017).</li><li>Yohn, C. N., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Chronic+non-discriminatory+social+defeat+is+an+effective+chronic+stress+paradigm+for+both+male+and+female+mice.">Chronic non-discriminatory social defeat is an effective chronic stress paradigm for both male and female mice.</a> Neuropsychopharmacology. 44 (13), 2220-2229 (2019).</li><li>Krishnan, V., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Molecular+adaptations+underlying+susceptibility+and+resistance+to+social+defeat+in+brain+reward+regions.">Molecular adaptations underlying susceptibility and resistance to social defeat in brain reward regions.</a> Cell. 131 (2), 391-404 (2007).</li><li>I&#241;iguez, S. D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Vicarious+Social+Defeat+Stress+Induces+Depression-Related+Outcomes+in+Female+Mice.">Vicarious Social Defeat Stress Induces Depression-Related Outcomes in Female Mice.</a> Biol Psychiatry. 83 (1), 9-17 (2018).</li><li>Newman, E. L., Leonard, M. Z., Arena, D. T., de Almeida, R. M., Miczek, K. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Social+defeat+stress+and+escalation+of+cocaine+and+alcohol+consumption:+Focus+on+CRF.">Social defeat stress and escalation of cocaine and alcohol consumption: Focus on CRF.</a> Neurobiology of Stress. 9, 151-165 (2018).</li><li>Nilsson, S. R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Simple+Behavioral+Analysis+(SimBA)+-+an+open+source+toolkit+for+computer+classification+of+complex+social+behaviors+in+experimental+animals.">Simple Behavioral Analysis (SimBA) - an open source toolkit for computer classification of complex social behaviors in experimental animals.</a> bioRxiv. , (2020).</li><li>Newman, E. L., Leonard, M. Z., Arena, D. T., de Almeida, R. M. M., Miczek, K. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Social+defeat+stress+and+escalation+of+cocaine+and+alcohol+consumption:+Focus+on+CRF.">Social defeat stress and escalation of cocaine and alcohol consumption: Focus on CRF.</a> Neurobiology of Stress. 9, 151-165 (2018).</li></ol>

The authors have nothing to disclose.

While the chronic CORT paradigm provides a constant CORT dose in the drinking water, from experience there can be some variability in amount consumed by mice. Further, consumption can only be assessed for the total cage, and an average taken based on the number of mice in the cage. Additionally, spillage can occur when weighing the bottles, transferring the mice for behavior testing, or when changing to a fresh cage. However, tracking Vehicle and CORT consumption is still feasible and accurate across weeks of treatment a...

Mood disorders such as depression and anxiety are highly prevalent in today&#8217;s society. Decades of work has continuously searched for improved treatments and relevant rodent models to study these complex disorders1. Chronic stress is a contributing factor for mood disorders like depression2. Therefore, chronic stress paradigms such as chronic social defeat stress (SDS) and chronic corticosterone administration (CORT) were developed in male mice and are now widely used to assess the neurobiological and behavioral effects of chronic stress exposure. The most widely used behavioral tests for assessing chronic stress effects include tasks associated with avoidance behavior, such as elevated plus maze, open field, and novelty suppressed feeding, or with antidepressant efficacy, such as forced swim test. However, these behaviors in rodents arguably lack face and, more importantly, predictive validity and translational relevance for human disorders such as depression.
A popular chronic stress paradigm, chronic unpredictable mild stress (CUMS), has been validated extensively using behaviors such as sucrose preference3. CUMS reduces preference for a 1% sucrose solution compared to water and is historically interpreted as anhedonia-related behavior4,5. However, this reduction in sucrose preference is not observed in humans with major depressive disorder6,7. In addition, sucrose preference does not allow for the study of effortful reward motivation.
Recently, some research has shifted focus to other behaviors associated with motivation and reward8,9. These tasks have promising translational value because relatively similar behavior assessments can be conducted in both humans and rodents. Here, we describe the CORT and SDS paradigms and their effects in a Y-maze barrier behavioral task that measures motivation to exert effort for reward. We then discuss a new chronic stress paradigm that we developed, chronic non-discriminatory social defeat stress (CNSDS), which is effective in both male and female mice.
Chronic corticosterone administration (CORT) is a paradigm designed to mimic chronic stress without actual stress exposures. Activation of the hypothalamus-pituitary-adrenal axis by stress results in the endogenous release of the adrenal steroid cortisol in humans10,11,12 and corticosterone in mice13,14. Delivery of corticosterone through the drinking water of adult male mice for at least 4 weeks results in maladaptive behavioral responses in avoidance tasks such as open field, elevated plus maze, and novelty suppressed feeding10,11,12,13,14,15,16. Interestingly, CORT also affects reward processing in instrumental tasks16,17,18,19. The CORT paradigm described here produces a consistent serum concentration of below 100 ng/mL CORT, which is more than five times less than that produced by an acute stressor such as forced swim15. Therefore, chronic CORT administration is unlikely to cause hypercortisolemia. While chronic CORT is only effective in male mice20, we recently demonstrated that it produces a robust shift in effortful responding in the Y-maze barrier task21. To our knowledge, this was one of the first studies to examine the effects of chronic stress on an effort-related choice behavior in male mice21. One previous study first demonstrated the impact of acute restraint stress on effort-based decision making in rats22. In effort-related choice behaviors, an animal chooses to either exert effort for a high-value reward or accept a lower-value reward that is more freely available. In humans, the effort-expenditure for rewards task (EEfRT), is a computer game developed to be analogous to effort-related choice tasks in mice23. Depression results in maladaptive responses in EEfRT (decreased likelihood of choosing hard tasks for high-value rewards). Therefore, effort-related choice tasks in rodents are particularly interesting because of their translational relevance.
Chronic social defeat stress (SDS) is one of the more widely used preclinical stress models in male mice. It is a 10-day protocol where large, aggressive retired breeder CD-1 males attack experimental mice, typically C57BL/6J, in 5 min daily sessions24. This produces a robust maladaptive behavioral phenotype in a subset of experimental mice. A social interaction test is used to stratify mice into resilient or susceptible populations to the defeat stress, and several studies have used this unique characteristic of SDS to probe the molecular and neural circuit mechanisms underlying stress reliance and susceptibility. Here we describe the details of the CORT paradigm and its implementation for the Y-maze barrier behavioral task. We also discuss SDS effects in the Y-maze barrier task. The Y-maze barrier task is based on the T-maze barrier task, which is used primarily in rats to measure motivation to expend effort for high or low rewards present in the two arms of the maze8,9,25. This task has also been implemented to study effortful responding in mice administered caffeine or dopamine antagonists in mice26. Rodents can either expend greater effort by climbing barriers of progressively increasing height in one arm of the maze for a higher reward value, typically 4 reward pellets, or expend significantly less effort in the other arm of the maze to receive only 2 reward pellets9. 10-day social defeat paradigms produce a robust maladaptive phenotype in susceptible mice that lasts approximately 30 days, so we modified the Y-maze barrier task to more rapidly train and test animals in order to complete all experiments within this 30-day timeframe24. Therefore, here we also detail a Y-maze barrier behavioral task protocol containing condensed training sessions and single barrier test sessions to measure motivation to expend effort for reward in chronic stress-exposed mice.
Unfortunately, both chronic corticosterone and chronic social defeat stress were developed in male mice and are less effective in female mice. This is highly problematic as women are more likely than men to be diagnosed with mood disorders such as depression1. Clever adaptations to SDS have allowed usage in female mice but require difficult surgeries or tedious urine collection26,27. We recently described a simple modification to the SDS paradigm, called chronic non-discriminatory social defeat stress (CNSDS). CNSDS allows susceptible and resilient stratification of both experimental male and female mice28. Both female and male susceptible mice exposed to CNSDS show increased avoidance of open arms in elevated-plus maze and of the center in open field and display increased latency to eat in novelty-suppressed feeding. CNSDS also is more efficient than other modifications to SDS, as both sexes are combined in defeat sessions. This results in an increased yield of experimental mice without an associated increase in time and effort required to complete the protocol. Therefore, we conclude this manuscript with an in-depth presentation of this recently developed chronic stress paradigm.

<table><tbody><tr><td>Acrylic Sheet</td><td>McMaster Carr</td><td>8560K215</td><td>Clear, 3/16&quot; thick, 24&quot; X 36&quot;</td></tr><tr><td>Beta-cyclodextrin</td><td>Sigma-Aldrich</td><td>C4767</td><td>500 mg</td></tr><tr><td>C57BL/6J Mice</td><td>Jackson Labs</td><td>000664</td><td>Adults age 7-8 weeks</td></tr><tr><td>Corticosterone</td><td>Sigma-Aldrich</td><td>C2505 or C27840</td><td>100 or 500 mg</td></tr><tr><td>Male CD-1 Mice</td><td>Charles River</td><td>022</td><td>&quot;Retired Breeders&quot;</td></tr><tr><td>PVC Acrylic Sheet</td><td>McMaster Carr</td><td>8560K215</td><td>White, 3/16&quot; thick, 48&quot; X 48&quot;</td></tr><tr><td>Solidstate Ultrasonic Cleaner</td><td>Fisher Scientific</td><td>FS-28</td><td>Must reach 40 kHz</td></tr><tr><td>Steel Wire Cloth</td><td>McMaster Carr</td><td>9219T143</td><td>1 ft X 2 ft</td></tr></tbody></table>

chronic stress shifts effort-related choice behavior in a y-maze barrier task in mice

Mood disorders, including major depressive disorder, can be precipitated by chronic stress. The Y-maze barrier task is an effort-related choice test that measures motivation to expend effort and obtain reward. In mice, chronic stress exposure significantly impacts motivation to work for a higher value reward when a lesser value reward is freely available compared to unstressed mice. Here we describe the chronic corticosterone administration paradigm, which produces a shift in effortful responding in the Y-maze barrier task. In the Y-maze task, one arm contains 4 food pellets, while the other arm contains only 2 pellets. After mice learn to select the high reward arm, barriers with progressively increasing height are then introduced into the high reward arm over multiple test sessions. Unfortunately, most chronic stress paradigms (including corticosterone and social defeat) were developed in male mice and are less effective in female mice. Therefore, we also discuss chronic non-discriminatory social defeat stress (CNSDS), a stress paradigm we developed that is effective in both male and female mice. Repeating results with multiple distinct chronic stressors in male and female mice combined with increased usage of translationally relevant behavior tasks will help to advance the understanding of how chronic stress can precipitate mood disorders.

Chronic CORT was administered for 4 weeks followed by Y-maze barrier training and testing (Figure 1A). In a separate cohort, the 10-day SDS paradigm was similarly followed by training and testing in the Y-maze barrier task (Figure 1C), to determine the effect of these chronic stress paradigms on effort-related choice behavior in male mice. Chronic CORT and SDS both reduced mean body weight compared to Vehicle mice and SDS Control mice as determined by t...

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Chronic Stress Shifts Effort-Related Choice Behavior in a Y-Maze Barrier Task in Mice

The Y-maze barrier task is a behavior test that examines motivation to expend effort for reward. Here, we discuss testing multiple well-validated chronic stressors including chronic corticosterone and social defeat stress with this behavior, as well as the novel chronic non-discriminatory social defeat stress (CNSDS), which is effective in females.

Mood disorders, including major depressive disorder, can be precipitated by chronic stress. The Y-maze barrier task is an effort-related choice test that ...

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11.0K Views.  The State University of New Jersey. The Y-maze barrier task is a behavior test that examines motivation to expend effort for reward. Here, we discuss testing multiple well-validated chronic stressors including chronic corticosterone and social defeat stress with this behavior, as well as the novel chronic non-discriminatory social defeat stress (CNSDS), which is effective in females.

Video: Chronic Stress Shifts Effort-Related Choice Behavior in a Y-Maze Barrier Task in Mice

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 ...

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.

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 ...

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 ...

Low-cost Protocol of Footprint Analysis and Hanging Box Test for Mice Applied the Chronic Restraint Stress

Gait disturbance is frequently observed in patients with movement disorders. In mouse models used for movement disorders, gait analysis is important behavioral test to determine whether the mice mimic the symptoms of patients. Motor deficits are often induced by stress when no spontaneous motor phenotype is observed in the mouse models. Therefore, gait analysis followed by stress loading would be a sensitive method for evaluating the motor phenotype in mouse models. However, researchers face the requirement of an expensive apparatus to obtain quantitative results automatically from gait analysis. For stress, stress loading by simple methods without expensive apparatuses required for electric shock and forced running is desirable. Therefore, we introduce a simple and low-cost protocol consisting of footprint analysis with paper and ink, hanging box test to evaluate motor function, and stress loading defined by restraint with a conical tube. The motor deficits of mice were successfully detected by this protocol.

The low-cost protocol consisting of footprint analysis and hanging box test after restraint stress is useful for evaluating the movement disorders of mouse model.

Gait disturbance is frequently observed in patients with movement disorders. In mouse models used for movement disorders, gait analysis is important ...

A Chronic Immobilization Stress Protocol for Inducing Depression-Like Behavior in Mice

Depression is not yet fully understood, but various causative factors have been reported. Recently, the prevalence of depression has increased. However, therapeutic treatments for depression or research on depression is scarce. Thus, in the present paper, we propose a mouse model of depression induced by movement restriction. Chronic mild stress (CMS) is a well-known technique to induce depressive-like behavior. However, it necessitates a complex procedure consisting of a combination of various mild stresses. In contrast, chronic immobilization stress (CIS) is a readily accessible chronic stress model, modified from a restraint model that induces depressive behavior by restricting movement using a restrainer for a certain period. To evaluate the depressive-like behaviors, the sucrose preference test (SPT), the tail suspension test (TST), and the ELISA assay to measure stress marker corticosterone levels are combined in the present experiment. The described protocols illustrate the induction of CIS and evaluation of the changes in behavior and physiological factors for the validation of depression.

This article provides a simplified and standardized protocol for induction of depressive-like behavior in chronically immobilized mice by using a restrainer. In addition, behavior and physiological techniques to verify induction of depression are explained.

Depression is not yet fully understood, but various causative factors have been reported. Recently, the prevalence of depression has increased. However, ...

Assessment of Stress Effects on Cognitive Flexibility using an Operant Strategy Shifting Paradigm

Stress affects cognitive function. Whether stress enhances or impairs cognitive function depends on several factors, including the 1) type, intensity, and duration of the stressor; 2) type of cognitive function under study; and 3) timing of the stressor in relation to learning or executing the cognitive task. Furthermore, sex differences among the effects of stress on cognitive function have been widely documented. Described here is an adaptation of an automated operant strategy shifting paradigm to assess how variations in stress affect cognitive flexibility in male and female Sprague Dawley rats. Specifically, restraint stress is used before or after training in this operant-based task to examine how stress affects cognitive performance in both sexes. Particular brain areas associated with each task in this automated paradigm have been well-established (i.e., the medial prefrontal cortex and orbitofrontal cortex). This allows for targeted manipulations during the experiment or the assessment of particular genes and proteins in these regions upon completion of the paradigm. This paradigm also allows for the detection of different types of performance errors that occur after stress, each of which has defined neural substrates. Also identified are distinct sex differences in perseverative errors after a repeated restraint stress paradigm. The use of these techniques in a preclinical model may reveal how stress affects the brain and impairs cognition in psychiatric disorders, such as post-traumatic stress disorder (PTSD) and major depressive disorder (MDD), which display marked sex differences in prevalence.

Stressful life events impair cognitive function, increasing the risk of psychiatric disorders. This protocol illustrates how stress affects cognitive flexibility using an automated operant strategy shifting paradigm in male and female Sprague Dawley rats. Specific brain areas underlying particular behaviors are discussed, and translational relevance of results are explored.

Stress affects cognitive function. Whether stress enhances or impairs cognitive function depends on several factors, including the 1) type, intensity, and ...

Threat-Safety Test for Stress Susceptibility or Resilience in Mice Models

Social Threat-Safety Test Uncovers Psychosocial Stress-Related Phenotypes

Social stress is a major cause of the development of mental disorders. To enhance the translational value of preclinical studies, social stress experience and its behavioral impact on mice should be comparable to humans. Chronic social defeat (CSD) utilizes a type of social stress involving physical attacks and sensory threats to induce mental dysfunctions resembling human affective disorders. To strengthen the psychosocial component of CSD, a 10-day CSD protocol was applied in which daily physical attacks are standardized to three 10 s episodes followed by a 24 h sensory phase. After the 10th sensory phase, the CSD protocol is followed by a refined behavioral assay called the social threat-safety test (STST). Post-stress behavioral assays need to determine how and to what extent the social stressor has influenced behavior. The STST allows chronically socially defeated male mice to interact with 2 novel male individuals (social targets): one social target from the attacking strain encountered during the CSD days and the other from a novel strain. Both are presented simultaneously in different compartments of a three-chambered test arena. The test enables a simultaneous assessment of social avoidance development to measure successful aversive conditioned learning and social threat-safety discrimination ability. The development of social avoidance towards both strains reflects a generalized aversive response and thus, a measurement of stress susceptibility. Meanwhile, the development of social avoidance towards only the attacking strain reflects threat-safety discrimination and thus, a measurement of stress resilience. Finally, the absence of social avoidance towards the attacking strain reflects impaired aversive conditioned learning. The protocol aims to refine the currently used mouse models of stress susceptibility/resilience by including translational criteria, specifically threat-safety discrimination and aversive response generalization, to categorize a single group of chronically socially defeated animals into resilient and susceptible subgroups, eventually advancing future translational approaches.

Author Spotlight: Unveiling Mechanisms of Stress Resilience - Significant Findings, Advancements, and Future Research

The social threat-safety test allows a simultaneous assessment of social avoidance development as a measurement of aversive conditioned learning and social threat-safety discrimination ability, both utilized to identify stress-susceptible and stress-resilient individuals within a single group of chronically socially defeated male mice.

Social stress is a major cause of the development of mental disorders. To enhance the translational value of preclinical studies, social stress experience ...

Modeling Early Life Trauma in Mice to Study PTSD and Social Avoidance Behavior

Chronic Social Defeat Stress in Early Adolescent Male Mice

Physical abuse and trauma in childhood is reported in as many as 1 in 7 children and is a major risk factor for the development of psychiatric diseases, such as Post-Traumatic Stress Disorder (PTSD), in adolescence and adulthood. Hallmark behavioral symptoms of PTSD include avoidance of cues and contexts associated with trauma. The ability to model long-lasting changes in the brain due to early life trauma is critical to determine potential circuit and molecular targets for the modulation of resultant symptoms. This manuscript describes a protocol for modeling early life physical and psychological trauma in early adolescent male mice that produces socially avoidant behavior. Adolescent male mice are exposed to repeated aggressive encounters followed by overnight housing, which provides an added dimension of psychological stress, with an adult male aggressor every day for 10 days. Repeated social defeat paired with overnight housing by the aggressor in early adolescence produces robust social avoidance behavior that lasts throughout adulthood. Social avoidance can be readily quantified in early adolescents, adolescents, and adults using open field social interaction testing. Early adolescent social defeat robustly produces more than 60% susceptible animals in adulthood.

This protocol details how to perform 10 day chronic social defeat stress in early adolescent male mice to produce long-lasting social avoidance in adulthood in more than 60% of mice.

Physical abuse and trauma in childhood is reported in as many as 1 in 7 children and is a major risk factor for the development of psychiatric diseases, ...

Adolescent Social Stress Paradigm in C57BL&#47;6 Mice for Behavioral Research

Social Defeat Stress Model for Adolescent C57BL&#47;6 Male and Female Mice

Social adversity in adolescence is prevalent and can negatively impact mental health trajectories. Modeling social stress in adolescent male and female rodents is needed to understand its effects on ongoing brain development and behavioral outcomes. The chronic social defeat stress paradigm (CSDS) has been widely used to model social stress in adult C57BL/6 male mice by leveraging on the aggressive behavior displayed by an adult male rodent to an intruder invading its territory. An advantage of this paradigm is that it allows to categorize defeated mice into resilient and susceptible groups based on their individual differences in social behavior 24 h after the last defeat session. Implementing this model in adolescent C57BL/6 mice has been challenging because adult or adolescent mice do not typically attack early adolescent male or female mice and because adolescence is a short period of life, encompassing discreet temporal windows of vulnerability. This limitation was overcome by adapting an accelerated version of the CSDS to be used for adolescent male and female mice. This 4-day stress paradigm with 2 physical attack sessions per day uses a C57BL/6 male adult to prime the CD-1 mouse for aggressiveness such that it readily attacks the male or female adolescent mouse. This model was termed accelerated social defeat stress (AcSD) for adolescent mice. Adolescent exposure to AcSD induces social avoidance 24 h later in both males and females, but only in a subset of defeated mice. This vulnerability occurs despite the number of attacks being consistent across sessions between resilient and susceptible groups. The AcSD model is short enough to allow exposure during discrete periods within adolescence, allows the segregation of mice according to the presence or absence of social avoidance behavior, and is the first model available to study social defeat stress in adolescent C57BL/6 female mice.

Author Spotlight: Understanding Adolescent Social Adversity Effects on Neurodevelopment in Mice

We developed an accelerated social defeat stress model for adolescent C57BL/6 mice, which works in both males and females and allows exposure during discrete adolescent periods. Exposure to this model induces social avoidance, but only in a subset of defeated male and female mice.

Social adversity in adolescence is prevalent and can negatively impact mental health trajectories. Modeling social stress in adolescent male and female ...

Neuroscience

Modeling Early-Life Adversity in Mice Using Limited Bedding and Nesting

Limited Bedding and Nesting as a Model for Early-Life Adversity in Mice

Early-life adversity (ELA), such as abuse, neglect, lack of resources, and an unpredictable home environment, is a known risk factor for developing neuropsychiatric disorders such as depression. Animal models for ELA have been used to study the impact of chronic stress on brain development, and typically rely on manipulating the quality and/or quantity of maternal care, as this is the major source of early-life experiences in mammals, including humans. Here, a detailed protocol for employing the Limited Bedding and Nesting (LBN) model in mice is provided. This model mimics a low-resource environment, which provokes fragmented and unpredictable patterns of maternal care during a critical developmental window (postnatal days 2-9) by limiting the amount of nesting materials given to the dam to build a nest for her pups and separating the mice from the bedding via a mesh platform in the cage. Representative data are provided to illustrate the changes in maternal behavior, as well as the diminished pup weights and long-term changes in basal corticosterone levels, that result from the LBN model. As adults, offspring reared&#160;in the LBN environment have been shown to exhibit an aberrant stress response, cognitive deficits, and anhedonia-like behavior. Therefore, this model is an important tool to define how the maturation of stress-sensitive brain circuits is altered by ELA and results in long-term behavioral changes that confer vulnerability to mental disorders.

Author Spotlight: Exploring Microglial Interactions with Stress-Response Circuitry Using the Limited Bedding and Nesting Model

This protocol describes an animal model for studying how early-life adversity, provoked by an impoverished environment and unpredictable maternal care during the early postnatal period, affects brain development and the future risk of mental disorders.

Early-life adversity (ELA), such as abuse, neglect, lack of resources, and an unpredictable home environment, is a known risk factor for developing ...