Changes in Sociability and Preference for Social Novelty in Female Rats in Prolonged Social Isolation

Chronic stress due to social isolation (SI) can lead to distress with negative consequences for both humans and animals. Numerous disorders caused by SI include disorders in the emotional-motivational domain and cognitive functions, as well as changes in social behavior. There are currently no data identifying the sequelae of SI when its duration is significantly increased. Although female rats have been shown to be highly sensitive to stress, research on them is lacking. The present study assessed sociability and preference for "social novelty" in a three-chamber social test in female Wistar rats in two series of experiments at different time points during prolonged SI, which began at adolescence and continued to ages 5.5 and 9.5 months. At two months of SI, rats showed an increased preference for a social object over a non-social object (increased sociability) simultaneously with the appearance of signs of a decrease in the preference for a new social object over an already familiar social object (signs of a decrease in the preference for social novelty). In a social interaction test, the rats also displayed increases in the durations of social contacts, including aggressive interactions; they showed a decrease in exploratory risk assessments (head dips from the open arms) in the elevated plus maze test and a decrease in exploratory activity. After SI lasting 8.5 months, the rats showed signs of social deficit and a marked decrease in the preference for social novelty. No signs of increased aggressiveness were found. Thus, the impact of SI on social behavior depended on its duration and, we believe, was accompanied by a change in coping strategies.