Social agency buffers pain sensitivity during a critical window following spared nerve injury

Social buffering of pain, where social contact blunts pain intensity, is well established. However, the degree to which agency over social contact, rather than passive social exposure alone, modifies pain intensity or social behavior is unclear.

Using a social operant self-administration procedure in which mice lever-press for access to their pair-housed partner, we show that voluntary social engagement gates pain after spared nerve injury (SNI). After 8 days of training, mice underwent SNI and then regained access to social self-administration either 1 day (Early) or 5 days (Delayed) following surgery. We compared these mice to groups without social self-administration access, non-contingent social-access, and food self-administration. We assessed changes in pain, or mechanical allodynia, via the von Frey test.

Early access to social self-administration after SNI preserved pre-injury social reinforcement and buffered pain. Delayed access similarly preserved social reinforcement but failed to buffer allodynia, revealing an early post-injury critical window for social buffering of pain. Females were more sensitive to both SNI and disrupted social access, while males maintained social reward-seeking after SNI when given early access and showed robust social buffering of pain. Non-contingent (involuntary) social self-administration did not modify pain, nor did food self-administration.

There is an early critical window during which voluntary social interactions buffer pain after nerve injury. These results highlight social reward agency and proximity to injury as key variables, since pain outcomes do not generalize to food reward, non-contingent social reward, or delayed access to social reward.