Lack of social touch alters anxiety-like and social behaviors in male mice

Abstract

The importance of social interactions has been reported in a variety of animal species. In human and rodent models, social isolation is known to alter social behaviors and change anxiety or depression levels. During the coronavirus pandemic, although people could communicate with each other through other sensory cues, social touch was mostly prohibited under different levels of physical distancing policies. These social restrictions inspired us to explore the necessity of physical contact, which has rarely been investigated in previous studies on mouse social interactions. We first conducted a long-term observation to show that pair-housed mice in a standard laboratory cage spent nearly half the day in direct physical contact with each other. Furthermore, we designed a split-housing condition to demonstrate that even with free access to visual, auditory, and olfactory social signals, the lack of social touch significantly increased anxiety-like behaviors and changed social behaviors. There were correspondingly higher levels of the pro-inflammatory cytokine interleukin-6 in the hippocampus in mice with no access to physical contact. Our study demonstrated the necessity of social touch for the maintenance of mental health in mice and could have important implications for human social interactions.

Keywords:

• Social touch
• social isolation
• anxiety-like behaviors
• social behaviors
• cytokines

Acknowledgements

The authors thank the members of the Kuo and Lin labs for experimental help. We also thank National Yang Ming Chiao Tung University for the mouse facility.

Disclosure statement

The authors declare no competing financial interests.

Ethics approval and consent to participate

All animal procedures were in compliance with institutional guidelines established and approved by the Institutional Animal Care and Use Committee of National Tsing Hua University.

Author contributions

K-T Lin, and T-H Kuo designed the experiments; Y-K Ma, C-L Lee, Y-H Chu, C-H Chen, and Y-S Su performed the experiments; Y-K Ma, P-Y Zeng, Y-H Chu, and C-C Cheng analyzed the data; K-T Lin and T-H Kuo wrote the manuscript.

Data availability statement

All data generated or analyzed during this study are included in this published article and its supplementary information files.

Additional information

Funding

The work was supported by. [MOST 108-2314-B-007-003-MY3 to K-T Lin] [MOST 108-2636-B-007-002 Young Scholar Fellowship to T-H Kuo], by the Higher Education Sprout Project funded by Ministry of Education and the Ministry of Science and Technology to the Brain Research Center (to T-H Kuo).