Difference in Endocrine and Behavior between Short-Term Single- And Paired-Housing Mice in Metabolic Cage

Abstract

Metabolic cage housing which is exposed to a number of environmental stressors is often used in pharmacokinetic studies. In this study, we compared the difference in stress response between single- and paired-housing in metabolic cages by evaluating the alteration of urinary stress hormones and behavior. Mice were randomly divided into single- or paired-housing groups and placed in a metabolic cage with wire mesh. Their urine was collected every 24 hours for consecutive 4 days to determine excreted catecholamine and corticosterone. The change in body weight was significantly decreased at 3 and 4 days in the single-housing group compared with that before the experiment, but not paired-housing group. The level of urinary catecholamines, such as noradrenaline, adrenaline, and their metabolite vanillylmandelic acid, was significantly increased in the single-housing compared with paired housing group and urinary corticosterone increased as well. Next, for the two similarly housed groups, we observed spontaneous behavior on the fourth day and conducted an elevated cross-maze test on the fifth day. Spontaneous behavior was not different between experimental groups. In the elevated cross-maze test, the proportion of time spent in the open arms was significantly prolonged in the paired-housing group compared to that of the single-housing group.  Short-term social isolation stress loading in metabolic cages was suggested to exhibit endocrinological and behavioral changes in mice. To reduce such interference due to stress exposure, it was suggested to keep two mice in a metabolic cage.

Note:
Funding declaration: This work was supported by JSPS KAKENHI (Grant Number 19H04036).

Conflicts of Interest: None

Ethical Approval: The present study was approved by the Animal Care and Use Committee of the Shibaura Institute of Technology (Permit Number, AEA21008) and conducted to comply with the ARRIVE guidelines and in accordance with the National Research Council's Guide for the Care and Use of Laboratory Animals.

Keywords: Social isolation stress, catecholamine, corticosterone, Anxiety