Social transfer of pain in mice

I recently read this great paper that found that “bystander” mice housed in the same room as mice in a heightened pain state (CFA, opioid withdrawal, or EtOH withdrawal) showed a reduction in pain thresholds for both mechanical and thermal stimuli. This transfer of pain occurs via olfactory cues, and isn’t dependent on a concurrent state of anxiety or heightened CORT levels.

This paper lead me to reconsider how we house our rodents in pain studies and has admittedly made me a little paranoid about social confounds in pain studies. If you’re starting a behavioral cohort, consider filter tops on your cages!

1 Like

Thanks for sharing this paper @runDRG. Indeed, if this is true and a general effect, it would influence all of our behavior assays. I’m not sure how we would practically change anything though. 20 rooms for 20 separate animals?

Here is there take on the implications:

The current findings also have broader methodological implications for rodent studies. It is common for experimental groups to be housed and tested with or near their respective comparison groups to control for environmental confounds. The present findings demonstrate that a physiologically relevant behavioral state can be transmitted between rodents housed throughout a room via olfactory cues. Although the experimental conditions used here may have maximized the potential for social transfer via an olfactory channel (cages had wire tops with no filter lids to permit access to drinking bottles, and the mice were tested in the room in which they were housed), the manner in which the experimental animals are housed and tested should be considered as a factor in the experimental design. Our findings expand the concern raised by a recent study, which has suggested that mice undergoing neuropathic pain can induce hypernociception in cagemates (10). It will be important in future studies to determine the various environmental and test conditions in which social transfer of pain occurs. For example, it is possible that filter tops or cage filtration could reduce the exposure to olfactory cues and, in turn, attenuate the development of hyperalgesia in bystanders.