title: Long-term effects of the periadolescent environment on exploratory activity and aggressive behaviour in mice: social versus physical enrichment.
abstract: The aims of the present study were (i) to investigate the effects of environmental enrichment during periadolescence on different behavioural and neurochemical responses in male CD-1 mice at adulthood and (ii) to describe the relative role of the physical and social components of the enrichment in producing these effects. Thirty 5-day-old mice were randomly assigned to one of the following housing conditions lasting five consecutive days: (i) individually housed in a standard cage, (ii) housed in pairs in a standard cage, (iii) individually housed in a physically enriched cage, and (iv) housed in pairs in a physically enriched cage. At adulthood, 80 days after the enrichment exposure, the explorative behaviour in an open field, as well as the behaviour in agonistic encounters, was evaluated in association with the analysis of selected central (hypothalamic levels of nerve growth factor (NGF) and brain-derived growth factor(BDNF)) and peripheral (plasma corticosterone levels) biochemical parameters. The results show that the long-term effects of the physical and the social enrichment are different and not additive. In particular, while social enrichment by itself exerted very limited effects, physical enrichment decreased the exploratory activity and altered social behaviour. Mice housed in pairs in an enriched cage showed low activity levels in the open field, and they tended to become more frequently dominant, although showing a more affiliative and less aggressive social interaction strategy. Furthermore, they presented low levels of hypothalamic NGF and high levels of brain-derived growth factor, suggesting an important effect of the combination of social and physical enrichment on neurobehavioral markers of brain plasticity and on animal ability to cope with social challenges.
authors.affiliation: Section of Behavioural Neurosciences, Department of Cell Biology and Neurosciences, Istituto Superiore di Sanità, Viale Regina Elena 299, 00161 Rome, Italy.
authors.forename: Susanna
authors.initials: S
authors.lastname: Pietropaolo
authors.forename: Igor
authors.initials: I
authors.lastname: Branchi
authors.forename: Francesca
authors.initials: F
authors.lastname: Cirulli
authors.forename: Flavia
authors.initials: F
authors.lastname: Chiarotti
authors.forename: Luigi
authors.initials: L
authors.lastname: Aloe
authors.forename: Enrico
authors.initials: E
authors.lastname: Alleva
mesh_terms: D000374:Aggression / Q000502:physiology*; D000818:Animals; D019208:Brain-Derived Neurotrophic Factor / Q000097:blood; D003345:Corticosterone / Q000097:blood; D004777:Environment; D004797:Enzyme-Linked Immunosorbent Assay; D005106:Exploratory Behavior / Q000502:physiology*; D005260:Female; D006120:Grooming; D007031:Hypothalamus / Q000378:metabolism; D008297:Male; D051379:Mice; D009414:Nerve Growth Factors / Q000097:blood; D009490:Neurosecretory Systems / Q000502:physiology; D011863:Radioimmunoassay; D051381:Rats; D012726:Sexual Behavior, Animal / Q000502:physiology; D012919:Social Behavior; D012931:Social Environment
chemical_list: D019208:Brain-Derived Neurotrophic Factor; D009414:Nerve Growth Factors; D003345:Corticosterone