title: Stereotypic behaviour in standard non-enriched cages is an alternative to depression-like responses in C57BL/6 mice.
abstract: Depressive-like forms of waking inactivity have been recently observed in laboratory primates and horses. We tested the hypotheses that being awake but motionless within the home-cage is a depression-like symptom in mice, and that in impoverished housing, it represents an alternative response to stereotypic behaviour. We raised C57BL/6 ('C57') and DBA/2 ('DBA') females to adulthood in non-enriched (n=62 mice) or enriched (n=60 mice) cages, observing home-cage behaviour during the active (dark) phases. We predicted that being still but awake would be reduced by environmental enrichment; more pronounced in C57s, as the strain most prone to learned helplessness; negatively related to stereotypic behaviour; and positively related to immobility in Forced Swim Tests (FST). Compared to enriched mice, non-enriched subjects did spend more time spent being inactive but awake, especially if they displayed relatively little stereotypic behaviour. C57 mice also spent more time awake but motionless than DBAs. Furthermore, even after statistically controlling for housing type and strain, this behaviour very strongly tended to predict increased immobility in the FST, while high levels of stereotypic behaviours in contrast predicted low immobility in the FST. Being awake but motionless is thus a reaction to non-enriched housing that seems to be an alternative to stereotypic behaviour, and could reflect depression-like states.
authors.affiliation: Animal Biosciences, University of Guelph, Ontario N1G 2W1, Canada. Electronic address: carole.fureix@bristol.ac.uk.
authors.forename: Carole
authors.initials: C
authors.lastname: Fureix
authors.affiliation: Animal Biosciences, University of Guelph, Ontario N1G 2W1, Canada.
authors.forename: Michael
authors.initials: M
authors.lastname: Walker
authors.affiliation: Animal Biosciences, University of Guelph, Ontario N1G 2W1, Canada.
authors.forename: Laura
authors.initials: L
authors.lastname: Harper
authors.affiliation: Molecular & Cellular Biology, University of Guelph, Ontario N1G 2W1, Canada.
authors.forename: Kathryn
authors.initials: K
authors.lastname: Reynolds
authors.affiliation: Animal Biosciences, University of Guelph, Ontario N1G 2W1, Canada.
authors.forename: Amanda
authors.initials: A
authors.lastname: Saldivia-Woo
authors.affiliation: Animal Biosciences, University of Guelph, Ontario N1G 2W1, Canada. Electronic address: gmason@uoguelph.ca.
authors.forename: Georgia
authors.initials: G
authors.lastname: Mason
mesh_terms: D000818:Animals; D003863:Depression / Q000235:genetics / Q000451:nursing* / Q000503:physiopathology*; D004195:Disease Models, Animal; D004777:Environment; D046353:Immobility Response, Tonic / Q000502:physiology; D016014:Linear Models; D051379:Mice; D008810:Mice, Inbred C57BL; D008811:Mice, Inbred DBA; D013045:Species Specificity; D013239:Stereotyped Behavior / Q000502:physiology*; D013550:Swimming / Q000523:psychology
keywords: Depression; Environmental enrichment; Forced Swim Test; Inactivity; Mice; Stereotypic behaviour