title: Subcaste differences in neural activation suggest a prosocial role for oxytocin in eusocial naked mole-rats.
abstract: The neuropeptide oxytocin (OT) influences prosocial behavior(s), aggression, and stress responsiveness, and these diverse effects are regulated in a species- and context-specific manner. The naked mole-rat (Heterocephalus glaber) is a unique species with which to study context-dependent effects of OT, exhibiting a strict social hierarchy with behavioral specialization within the subordinate caste: soldiers are aggressive and defend colonies against unfamiliar conspecifics while workers are prosocial and contribute to in-colony behaviors such as pup care. To determine if OT is involved in subcaste-specific behaviors, we compared behavioral responses between workers and soldiers of both sexes during a modified resident/intruder paradigm, and quantified activation of OT neurons in the hypothalamic paraventricular nucleus (PVN) and supraoptic nucleus (SON) using the immediate-early-gene marker c-fos co-localized with OT neurons. Resident workers and soldiers were age-matched with unfamiliar worker stimulus animals as intruders, and encounters were videorecorded and scored for aggressive behaviors. Colony-matched controls were left in their home colony for the duration of the encounters. Brains were extracted and cell counts were conducted for OT immunoreactive (ir), c-fos-ir, and percentage of OT-c-fos double-labeled cells. Results indicate that resident workers were less aggressive but showed greater OT neural activity than soldiers. Furthermore, a linear model including social treatment, cortisol, and subcaste revealed that subcaste was the only significant predictor of OT-c-fos double-labeled cells in the PVN. These data suggest that in naked mole-rats OT promotes prosocial behaviors rather than aggression and that even within subordinates status exerts robust effects on brain and behavior.
authors.affiliation: Department of Psychology, University of Toronto Mississauga, Mississauga, ON L5L 1C6, Canada.
authors.forename: Georgia A
authors.initials: GA
authors.lastname: Hathaway
authors.affiliation: Department of Psychology, University of Toronto Mississauga, Mississauga, ON L5L 1C6, Canada.
authors.forename: Mariela
authors.initials: M
authors.lastname: Faykoo-Martinez
authors.affiliation: Department of Psychology, University of Toronto Mississauga, Mississauga, ON L5L 1C6, Canada.
authors.forename: Deane E
authors.initials: DE
authors.lastname: Peragine
authors.affiliation: Department of Psychology, University of Toronto Mississauga, Mississauga, ON L5L 1C6, Canada.
authors.forename: Skyler J
authors.initials: SJ
authors.lastname: Mooney
authors.affiliation: Department of Psychology, University of Toronto Mississauga, Mississauga, ON L5L 1C6, Canada; Departments of Cell & Systems Biology and Ecology & Evolutionary Biology, University of Toronto, Toronto, ON M5S 3G5, Canada. Electronic address: melissa.holmes@utoronto.ca.
authors.forename: Melissa M
authors.initials: MM
authors.lastname: Holmes
mesh_terms: D000374:Aggression / Q000187:drug effects; D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects* / Q000502:physiology; D001921:Brain / Q000187:drug effects; D005260:Female; D006608:Hierarchy, Social; D008297:Male; D019577:Mole Rats; D009474:Neurons / Q000187:drug effects* / Q000502:physiology; D010121:Oxytocin / Q000494:pharmacology*; D010286:Paraventricular Hypothalamic Nucleus / Q000166:cytology / Q000187:drug effects; D012919:Social Behavior; D013495:Supraoptic Nucleus / Q000166:cytology / Q000187:drug effects
chemical_list: D010121:Oxytocin
keywords: Aggression; Eusocial; Naked mole-rat; Oxytocin; Prosocial; Social status; Sub-caste; c-fos