Effects of Post-Weaning Social Isolation and Oxytocin on Adult Anxiety and Sociability in Female Rats

Abstract

Positive social interactions during childhood and adolescence are essential for human neurobehavioral development. All social animals show persistent physiological and behavioral deficits after extended periods of social isolation. Our goal was to determine whether post-weaning social isolation negatively impacts adult anxiety and sociability in female Long Evans rats. Additionally, we tested whether administration of the pro-social hormone, oxytocin, could prevent behavioral deficits induced by isolation. On post-natal day (PND) 21, subjects were randomly assigned to social isolation (n = 30) or group housing (n = 30). Half of the subjects in each housing condition received 1 mg/kg oxytocin every three days for thirty days. The other half received saline-vehicle control. On PND 51-52, anxiety was assessed in the elevated-plus-maze (EPM). Subjects were then group housed (“resocialization”) in novel triplets. Due to the potential influence of ovarian hormones on social motivation, daily vaginal cytology was initiated to track subjects’ estrous cycles. On PND 66-67, subjects completed a second EPM test. On PND 70-72, subjects’ social motivation was assessed using a three-chamber sociability apparatus. Isolated subjects exhibited higher anxiety in the first EPM test (immediately following isolation) compared to group housed subjects (p < 0.01). In the second EPM test, however, there were no group differences in anxiety, suggesting that the detrimental effects of post-weaning social isolation on anxiety had been redressed by resocialization. Also as predicted, previously isolated subjects exhibited reduced social motivation compared to group-housed subjects (p < 0.05). These findings suggest that post-weaning isolation leads to persistent social deficits that cannot be explained by an increase in generalized anxiety. Lastly, oxytocin treatment did not prevent the detrimental behavioral effects of post-weaning social isolation, which suggests that the developmental consequences of adolescent social deprivation may not be caused by reduced oxytocin output. Overall, this study substantiates the theory that early social isolation has detrimental effects on adult emotionality and behavior. Future animal research should continue to explore the potential clinical utility of oxytocin in treating social deficits.

Keywords

• social isolation
• development
• adolescence
• oxytocin
• anxiety
• sociability