Social Instability Stress in Adolescence and Social Interaction in Female Rats

Adolescence is a critical time of brain development for regions governing social behaviour and social learning. Social experiences influence the ongoing maturation of the neural structures and ultimately modify the social behaviour of adults in response to social cues. Social instability stress in adolescence (SS; daily 1-hour isolation + change of cage partner in postnatal days [PND] 30-45) leads to a long-lasting reduction in social interaction in SS rats compared with non-stressed (CTL) rats in males; here we investigate females. In a first experiment, we found that female rats exposed to adolescent SS also showed the decrement in social interaction irrespective of age at which tested, and replicated the effects previously found in males. In experiment 2, which involved females only, SS and CTL rats did not differ in anxiety-like behaviour in the elevated plus maze (EPM) and the reduction in social interaction was not significant. Nevertheless, when tested in adolescence at P47 (and not at P71), SS female rats had higher corticosterone release during the social interaction test than did CTL rats, and they exhibited a different pattern of neural activation as measured by immunoreactivity to the protein products of zif268 and c-fos (SS CTL in medial prefrontal cortex and SS CTL in hippocampus), and reduced oxytocin immunoreactivity in the paraventricular nucleus of the hypothalamus than did CTL rats. These results extend our previous findings of effects of SS in adolescent female rats on behavioural responses to psychostimulants to social behaviour, and point to directions for investigations of the neural mechanisms involved.