Evidence for a Role of Oxytocin Receptors in the Long-Term Establishment of Dominance Hierarchies

Abstract

Exposure to stress can affect the establishment of dominance hierarchies. In our model, a social hierarchy established by two male rats during a first encounter is not maintained 1 week later. If one of the two rats is stressed, the stressed rat becomes subordinate and the hierarchy that is formed is maintained. In this study, we investigated the changes in the expression of oxytocin (Otr) and vasopressin (V1aR) receptor genes in the medial amygdala (MeA) and the lateral septum (LS) in the hours following hierarchy establishment under both stressed and basal conditions. We found that the potentiation of a social hierarchy induced by stress is accompanied by social status- and region-specific changes in the expression of Otr mRNA in the MeA 3 h after the social encounter. At this time point, no evidence was found for the regulation of V1aR mRNA in any of the brain regions examined. Results from pharmacological experiments involving the microinfusion of a specific OTR antagonist immediately after the acquisition of a subordinate status under basal, non-stress conditions suggested a role for this receptor in the MeA on the long-term establishment of the subordinate status. Altogether, these findings highlight a role for the oxytocinergic system in the mechanisms through which stress facilitates the long-term establishment of a social hierarchy.

Stress and the social brain: behavioural effects and neurobiological mechanisms

“…In one study, acute intracerebral administration of oxytocin reversed the social avoidance and reduced social preference elicited by prior social defeat stress in rodents 155 . In another study, a reduction in oxytocin receptor expression in the medial amygdala 156 was found in male rats that acquire a long-term subordinate status as a result of application of an acute stressor just before being exposed to a social contest against a non-stressed rat 157 . Long-term subordination was also induced in rats without former exposure to stress by microinfusion of an oxytocin receptor antagonist in the medial amygdala immediately after hierarchy formation 156 , which suggests a role for the modulation of oxytocin receptors in stress-induced facilitation of long-term subordination.…”

“…In another study, a reduction in oxytocin receptor expression in the medial amygdala 156 was found in male rats that acquire a long-term subordinate status as a result of application of an acute stressor just before being exposed to a social contest against a non-stressed rat 157 . Long-term subordination was also induced in rats without former exposure to stress by microinfusion of an oxytocin receptor antagonist in the medial amygdala immediately after hierarchy formation 156 , which suggests a role for the modulation of oxytocin receptors in stress-induced facilitation of long-term subordination. This view is in agreement with the findings of pharmacological experiments that implicated oxytocin in the medial amygdala in the establishment of social memories in rats 158 .…”

Social memories in rodents: Methods, mechanisms and modulation by stress

“…Pharmacological experiments in which a specific OTR antagonist was infused into the MeA immediately after the acquisition of a subordinate status under basal, non-stress conditions suggested a role for this receptor in the MeA in the long-term establishment of subordinate status. Overall, these findings highlight a role for the oxytocinergic system in the mechanisms by which stress facilitates the long-term establishment of social hierarchy (Timmer et al, 2011).…”

“…More specifically, the role of OTR and V1aR in the MeA and lateral septum was investigated (Timmer et al, 2011). Potentiation of the social hierarchy by stress was found to be accompanied by social status-and region-specific changes in the expression of OTR gene (Otr) mRNA in the MeA 3 h after the social encounter.…”

Breaking the Dynamics of Emotions and Fear in Conflict and Reconstruction

“…However, existing knowledge about the neurobiological mechanisms underlying these complementary social processes is scarce. Timmer et al (2011) show that anxiety trait is highly predictive for social dominance; highly anxious (HA) animals tend to become submissive during an encounter when matched for weight to low anxious (LA) conspecifics as apparent from both total duration of offensive behavior (Figure 1, right panel).…”