The Long-Term Effects of Environmental Enrichment on Agonism in Female C57BL/6, DBA/2, and BALB/c Mice

Abstract

Female mice are usually kept in non-enriched shoebox cages that increase agonism. I sought to understand why environmental enrichment (EE) reduces agonism by observing home-cage agonism, stereotypic behaviour, and inactive-but-awake behaviour (IBA: a depressive-like state), and by assessing hearing loss and anxiety, in 165 mice (C57BL/6s, BALB/cs, and DBA/2s). I employed statistics to see if any of these variables predicted agonism; only IBA did in some sub-groups. Low agonism in EE mice was also partially explained by low social interaction rates. Lastly, I assessed agonism in an unfamiliar arena with stranger mice, but enriched mice did not exhibit less agonism in this setting. Overall, these findings demonstrate that a) EE reduces agonism in females, b) IBA co-varies with agonism, c) low agonism is partially a by-product of low interaction rates, and d) enriched mice are no less agonistic than non-enriched mice when in an unfamiliar arena with strangers.