title: An efficient chronic unpredictable stress protocol to induce stress-related responses in C57BL/6 mice.
abstract: Exposure to chronic stress can have broad effects on health ranging from increased predisposition for neuropsychiatric disorders to deregulation of immune responses. The chronic unpredictable stress (CUS) protocol has been widely used to study the impact of stress exposure in several animal models and consists in the random, intermittent, and unpredictable exposure to a variety of stressors during several weeks. CUS has consistently been shown to induce behavioral and immunological alterations typical of the chronic stress-response. Unfortunately C57BL/6 mice, one of the most widely used mouse strains, due to the great variety of genetically modified lines, seem to be resistant to the commonly used 4-week-long CUS protocol. The definition of an alternative CUS protocol allowing the use of C57BL/6 mice in chronic stress experiments is a need. Here, we show that by extending the CUS protocol to 8 weeks is possible to induce a chronic stress-response in C57BL/6 mice, as revealed by abrogated body weight gain, increased adrenals weight, and an overactive hypothalamic-pituitary-adrenal axis with increased levels of serum corticosterone. Moreover, we also observed stress-associated behavioral alterations, including the potentiation of anxious-like and depressive-like behaviors and a reduction of exploratory behavior, as well as subtle stress-related changes in the cell population of the thymus and of the spleen. The present protocol for C57BL/6 mice consistently triggers the spectrum of CUS-induced changes observed in rats and, thus, will be highly useful to researchers that need to use this particular mouse strain as an animal model of neuropsychiatric disorders and/or immune deregulation related to CUS.
authors.affiliation: Life and Health Sciences Research Institute (ICVS), School of Health Sciences, University of Minho , Braga , Portugal ; ICVS/3B's Research Group - PT Government Associate Laboratory , Braga , Portugal.
authors.forename: Susana
authors.initials: S
authors.lastname: Monteiro
authors.affiliation: Life and Health Sciences Research Institute (ICVS), School of Health Sciences, University of Minho , Braga , Portugal ; ICVS/3B's Research Group - PT Government Associate Laboratory , Braga , Portugal.
authors.forename: Susana
authors.initials: S
authors.lastname: Roque
authors.affiliation: Life and Health Sciences Research Institute (ICVS), School of Health Sciences, University of Minho , Braga , Portugal ; ICVS/3B's Research Group - PT Government Associate Laboratory , Braga , Portugal.
authors.forename: Daniela
authors.initials: D
authors.lastname: de Sá-Calçada
authors.affiliation: Life and Health Sciences Research Institute (ICVS), School of Health Sciences, University of Minho , Braga , Portugal ; ICVS/3B's Research Group - PT Government Associate Laboratory , Braga , Portugal.
authors.forename: Nuno
authors.initials: N
authors.lastname: Sousa
authors.affiliation: Life and Health Sciences Research Institute (ICVS), School of Health Sciences, University of Minho , Braga , Portugal ; ICVS/3B's Research Group - PT Government Associate Laboratory , Braga , Portugal.
authors.forename: Margarida
authors.initials: M
authors.lastname: Correia-Neves
authors.affiliation: Life and Health Sciences Research Institute (ICVS), School of Health Sciences, University of Minho , Braga , Portugal ; ICVS/3B's Research Group - PT Government Associate Laboratory , Braga , Portugal.
authors.forename: João José
authors.initials: JJ
authors.lastname: Cerqueira
keywords: CUS; anxiety; chronic stress; depressive-like behavior; immune dysfunction; neuropsychiatric disorders; social defeat