Differential effects of chronic fluoxetine on the behavior of dominant and subordinate naked mole-rats

•Naked mole-rats are eusocial rodents, living in large social groups with strict hierarchies.•Fluoxetine, a selective serotonin reuptake inhibitor, affects behavior in naked mole-rats in a status- and context-dependent manner.•Fluoxetine decreases aggression in dominant naked mole-rats when paired with unfamiliar animals.•Fluoxetine decreases digging behavior in subordinate naked mole-rats when in their home colony. Naked mole-rats are eusocial rodents that live in large subterranean colonies with a strict reproductive and social hierarchy. The breeding female (referred to as the queen) and 1 to 3 breeding males are the only reproductive members of the colony. Breeders are socially dominant and all other colony members are non-reproductive subordinates. The effects of manipulating the serotonergic neurotransmitter system on aggression and dominance behaviors are well studied in many species, but not in eusocial rodents like the naked mole-rat. The current study investigated how the serotonergic system influences aggressive/dominant behaviors in this species. To do this, two separate but related experiments were conducted: the effects of fluoxetine hydrochloride (FLX) on status-specific behaviors of subordinates (Experiment 1) and dominant queens (Experiment 2) were evaluated both in-colony and in a social-pairing paradigm. In accordance with our main hypothesis, chronic treatment of FLX attenuated the frequency and duration of aggression in queens, but not subordinates, when paired with an unfamiliar conspecific. Further exploration of pharmacological manipulation on status-specific behaviors of this eusocial species may elucidate the neurobiological mechanisms underlying their unique and rigid social hierarchy.