Behavioral outcomes in the bystander and demonstrator male mice following a socially-transferred allodynia paradigm

Abstract

The state of mechanical allodynia can be socially transferred from one individual to another during a brief empathetic contact. Our recent research has identified inter-individual differences in behavioral adaptations among bystander (BY) mice after a brief social contact with a demonstrator mouse experiencing complete Freund's Adjuvant (CFA)-induced inflammatory pain. However, the impact of the duration of social contact on the development of socially transferred allodynia is not yet clear. Additionally, it remains unknown whether social contact with different subgroups of BY mice differentially affects the pain behavior of CFA demonstrator mice. In the current study, we established a socially transferred allodynia paradigm with varying durations of social contact in male C57BL/6 J mice. We found that a 30-min or a longer social exposure to a CFA demonstrator mouse led to stable mechanical allodynia in naive BY mouse. As the duration of social contact increased, the persistence of the socially transferred allodynia also extended. Interestingly, the CFA demonstrator mice exhibited a partial reversal of mechanical allodynia when exposed to the BY mice for 24 h, but not for shorter durations. Surprisingly, this analgesic-like behavioral adaptation occurred only when the BY mice were susceptible to socially transferred allodynia. These findings demonstrate that behavioral adaptations in both BY and CFA demonstrator mice develop in a time-dependent manner. Additionally, the social contact-induced analgesic-like effect in CFA mice requires a specific cage mate that is susceptible to socially transferred allodynia.