Stress and the Development of Social behaviour in Adolescent Female Rats
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Adolescence is a critical time of brain development for regions governing social behaviour and social learning. In adolescence, social experiences may influence the ongoing maturation of the neural structures involved in social behaviour and ultimately modify the social behaviours 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 deficits in social behaviour in SS rats compared with non-stressed (CTL) rats in males; less is known in females. The main goal of my thesis is to investigate the effects of adolescent SS procedure on the development of social behaviour and brain regions underlying social behaviour in female rats when tested soon after and long after the end of the SS procedure. In the second chapter, I found that SS in male and female rats reduced time spent in social interaction when tested soon (PND 46) or long (PND 70) after the SS procedure in comparison to CTL rats. Irrespective of time post-stress and sex, SS rats spent less time in social interaction than did CTL rats, and female rats spent less time in social interaction than did male rats. The results from the third chapter demonstrated that SS females had higher corticosterone concentrations and lower Zif268 immunoreactive cell counts in the cingulate gyrus after the SI test than did CTLs when tested at PND 46. Furthermore, in the fourth chapter, brains were collected at PND 46 and PND 70 for RT-qPCR in female rats. Effects of SS on mRNA expression were observed for oxytocin receptor, vasopressin 1a receptor, corticotropin-releasing hormone receptor1, glucocorticoid receptor, and mineralocorticoid receptor that depended on age (time since the SS) and brain region (medial prefrontal cortex [mPFC], hippocampus). Some of the differences between SS and CTL rats were evident irrespective of age at which tested at PND 46 (such as GR in mPFC and MR in the hippocampus), whereas others emerged in adulthood at PND 70 (such as OTR and GR in the hippocampus).