Social status in mouse social hierarchies is associated with variation in oxytocin and vasopressin 1a receptor densities

Abstract

The neuropeptides oxytocin and vasopressin and their receptors have established roles in the regulation of mammalian social behavior including parental care, sex, affiliation and pair-bonding, but less is known regarding their relationship to social dominance and subordination within social hierarchies. We have previously demonstrated that male mice can form stable linear dominance hierarchies with individuals occupying one of three classes of social status: alpha, subdominant, subordinate. Alpha males exhibit high levels of aggression and rarely receive aggression. Subdominant males exhibit aggression towards subordinate males but also receive aggression from more dominant individuals. Subordinate males rarely exhibit aggression and receive aggression from more dominant males. Here, we examined whether variation in social status was associated with levels of oxytocin (OTR) and vasopressin 1a (V1aR) receptor binding in socially relevant brain regions. We found that socially dominant males had significantly higher OTR binding in the nucleus accumbens core than subordinate animals. Alpha males also had higher OTR binding in the anterior olfactory nucleus, posterior part of the cortical amygdala and rostral lateral septum compared to more subordinate individuals. Conversely, alpha males had lower V1aR binding in the rostral lateral septum and lateral preoptic area compared to subordinates. These observed relationships have two potential explanations. Preexisting individual differences in the patterns of OTR and V1aR binding may underlie behavioral differences that promote or inhibit the acquisition of social status. More likely, the differential social environments experienced by dominant and subordinate animals may shift receptor expression, potentially facilitating the expression of adaptive social behaviors. HighlightsO_LIMice living in social hierarchies express different levels of oxytocin receptor (OTR) and vasopressin 1a receptor (V1aR) binding in various brain regions according to their social status. C_LIO_LIAlphas and subdominants have higher OTR binding in the nucleus accumbens compared to subordinates. C_LIO_LIAlphas have higher OTR binding in the anterior olfactory nucleus compared to subdominants and subordinates. C_LIO_LIAlphas have higher OTR and lower V1aR binding in the rostral lateral septum compared to subordinates. C_LIO_LIAlphas have lower V1aR binding in the lateral preoptic area compared to subordinates. C_LI