Social instability stress in adolescent male rats reduces social interaction and social recognition performance and increases oxytocin receptor binding

- Adolescent social instability (SS) reduced the time spent interacting with unfamiliar peers.
- Control rats spent more time investigating for novel versus familiar rats and SS rats did not.
- SS rats did not differ from non-stressed controls in tests of social conditioned place preference.
- Adolescent SS enhanced oxytocin receptor binding density in the dorsal lateral septum and in the nucleus accumbens.

Social experiences in adolescence are essential for displaying context-appropriate social behaviors in adulthood. We previously found that adult male rats that underwent social instability stress (SS) in adolescence had reduced social interactions with unfamiliar peers compared with non-stressed controls (CTL). Here we determined whether SS altered social recognition and social reward and brain oxytocin and vasopressin receptor density in adolescence. We confirmed that SS rats spent less time interacting with unfamiliar peers than did CTL rats (p = 0.006). Furthermore, CTL rats showed a preference for novel over familiar conspecifics in a social recognition test whereas SS rats did not, which may reflect reduced recognition, impaired memory, or reduced preference for novelty in SS rats. The reward value of social interactions was not affected by SS based on conditioned place preference tests and based on the greater time SS rats spent investigating stimulus rats than did CTL rats when the stimulus rat was behind wire mesh (p = 0.03). Finally, oxytocin receptor binding density was higher in the dorsal lateral septum and nucleus accumbens shell in SS rats compared with CTL rats (p = 0.02, p = 0.01, respectively). No effect of SS was found for vasopressin 1a receptor binding density in any of the brain regions analyzed. We discuss the extent to which the differences in social behavior exhibited after social instability in adolescence involve changes in social salience and social competency, and the possibility that changes in oxytocin signaling in the brain underlie the differences in social behavior.