Acute partner loss enhances social motivation and nucleus accumbens dopamine release in prairie voles
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The loss of close social relationships triggers profound mental and physical health consequences across social species. We utilized the socially selective prairie vole (Microtus ochrogaster) to investigate how 5-day separation from a bonded mate or peer partner shapes social motivation and dopamine release kinetics in males and females. Prior to partner loss, baseline social motivation to access a partner or a novel object differed by sex and relationship type (mate or peer partnership). Across all groups, however, separation induced heightened partner-seeking. Partner loss enhanced dopamine signaling in the nucleus accumbens, increasing evoked dopamine release, the number of putative dopamine release sites, and tyrosine hydroxylase abundance, regardless of sex or relationship type. These findings suggest that mesolimbic reward circuitry rapidly adapts to the loss of a bonded partner, signaling a critical social deficit across relationship frameworks. Furthermore, by leveraging synthetic sensors, this study provides novel subcellular insights into presynaptic dopaminergic plasticity following 5-day relationship disruption, directly linking relationship loss to heightened social motivation and shifts in reward signaling.
Significance Statement
From friendships to mate partnerships, reciprocal social connections are vital for humans and other species that form social bonds. This study explores the behavioral and neural consequences of disrupting these relationships using the prairie vole, a species capable of forming selective bonds with both peers and mates. We demonstrate that, despite baseline sex and relationship-type differences in social reward, separation from a bonded partner triggers a uniform enhancement in social drive accompanied by elevated accumbal dopamine release and synthesis. This reveals a conserved, homeostatic reward mechanism that treats the loss of relationships as a critical deficit, advancing our understanding of the neurobiology of social bonding as well as grief and loneliness.
