Adolescent social isolation increases social behavior in Wistar rats: Role of post-weaning isolation housing on Social Familiarity-induced Anxiolysis (SoFiA) and social memory in adulthood.

Social connectedness is a critical part of adolescent development. Social support provides a robust facilitator for managing anxiety disorders that afflict nearly 1⁄3 of the U.S. adult population at some point in life. Consequently, it is important to understand the neurobiological mechanisms underlying the impact of social affiliation, or lack thereof, on treating or causing maladaptive anxiety states. In the current experiment, we manipulated the housing conditions in Wistar rats beginning on postnatal day (P) 21, rearing them in pairs (RP), in isolation (RI), or purchased adults rats reared at the facility (RF). We tested adult rats in the open field test, the social interaction habituation test (SI-Hab), which is a social safety learning animal model, and in the social recognition test (SRT), which is an animal model of sociability and social memory. Rats RI showed generalized increases in SI time compared to rats RP. However, there was no effect of rearing on acquisition of social safety during SI-Hab. During the SRT, rats RI exhibited a preference for a novel rat indicating robust social memory, whereas rats RP did not. Rats RF exhibited higher thigmotaxis relative to RP and RI and lower movement compared to RP in the novel open field. Numerous social and non-social behaviors were correlated with each other, and some depended on rearing condition. Based on correlation differences between RI and RP rats, RI history may be more conducive to the anxiolytic aspects of the SI-Hab protocol, which may improve the ability to deal with a perceived threat.