Exploring the similarities between risk factors triggering depression in humans and elevated in-cage “inactive but awake” behavior in laboratory mice

• DOI: 10.3389/fvets.2024.1348928
• Publication Date: 2024-03-28T13:59:56Z
• Authors: Oceane Schmitt; Emily Finnegan; Anna Trevarthen; Chanakarn Wongsae...; Elizabeth S. Paul; Michael Mendl; Carole Fureix
• Keywords: Cage; Depression

Depression is a human mental disorder that can also be inferred in non-human animals. This study explored whether time spent inactive but awake ("IBA") the home-cage mice was further triggered by risk factors similar to those increasing vulnerability depression humans (early life stress, genetic predispositions, adulthood stress). Eighteen DBA/2 J and 18 C57BL/6 females were tested, of which half underwent as pups daily maternal separation on post-natal days 2-14 (early-life stress "ELS") (other left undisturbed). To assess effect procedure, dams from subjects born active nest (proxy for behavior) recorded 2, 6, 10 14 1 h before following reunion (matched times controls), using live instantaneous scan sampling (total: 96 scans/dam). For each ELS condition, about housed post-weaning (i.e., 27 old average) either barren (triggering IBA depression-like symptoms) or larger, highly enriched cages (n = 4-5 per group). Time observed blind treatment two 90-min blocks, days/week, 6 weeks 192 scans/mouse). Data analyzed R generalized linear mixed models. The significantly more over (p 0.016), however with no significant difference between strains 0.18), conditions 0.20) before/after 0.83). As predicted, than < 0.0001). However, neither 0.4) nor strain 0.84) influenced IBA, interaction environmental condition (ELS × environment: p 0.2861; 0.5713). Our results therefore only partly support hypothesis greater depression. We discuss possible explanations this research directions.