Long-term Behavioral and Neuroendocrine Consequences of Early Adversity (Juvenile Stressor Exposure), and the Buffering Effects of ‘Comfort’ Food.

The adolescent period has been proposed to be exquisitely sensitive to the impacts of stress and juvenile stressor exposure is associated with anxiety- and depressive- like characteristics in adulthood. Among adult rats, access to a palatable diet has shown to mitigate the effects of stressors, a form of ‘self-medication.’ The present collection of studies sought to further characterize the long-term consequences of stressor exposure early in the juvenile period, as well as the use of palatable food as a coping strategy. The first study (Chapter 2) highlighted the importance of methodological rigor in the design of experiments employing social stressors. The second study (Chapter 3) provided further evidence that exposure to juvenile social defeat can have long-lasting consequences into adulthood, and access to a palatable diet may impart some resilience to initial stressor exposure. The third study (Chapter 4) demonstrated that access to a palatable diet can mitigate the long-term behavioral consequences of a 3-day sub chronic non-social stressor applied during juvenility in pair housed rats. The fourth study (Chapter 5) sought to replicate these findings in individually housed (purportedly more stressed) animals. Interestingly, access to a palatable diet was sufficient to protect against the neuroendocrine consequences of juvenile stress but did not mitigate the behavioral consequences, raising the question of an effectiveness “threshold” of self-medication via a palatable diet. The final study (Chapter 6) provided some preliminary evidence that exposure to juvenile stress amid access to a palatable diet has long-lasting changes on dopamine receptor expression in the nucleus accumbens, although the functional significance needs further characterization. Collectively, all studies provided further evidence that self-medication with a palatable diet comes at the price of poor metabolic outcomes. The results of this body of work provide further evidence that exposure to stress during juvenility can have protracted effects into adulthood, at the cost of poor metabolic outcomes. It also raises the suggestion of an effectiveness threshold of palatable food to cope with stress. Further understanding of the interplay between stress and diet may serve to inform the development of prevention based programs to mitigate the rising tide of concurrent childhood obesity and levels of perceived stress