Early life rearing of stressed animals in complex housing environment drives stress resilience in physiology, behavior and brain plasticity during adulthood

Abstract

Early-life maternal separation leads to hyper-reactive stress-response in adulthood along with long-lasting anxiogenic and depressive-like behavior. Maternal separation occurring during the vulnerable postnatal period interferes with the normal development of brain and its neuronal morphology. Most studies on maternal separation during early life highlight the dysregulation in emotional behavior of an individual in various stages of life. Emotional learning and memory are processed in amygdala. Thus, exploring the amygdala in maternally separated rats is crucial in understanding the mechanisms that drives emotional dysregulation in early-life stress model. Interestingly, recent studies showed that short-term enriched environment can enhance prominent innate behaviours like avoidance of predator odour and attractiveness of adult male rats. Additionally, short-term enrichment during adulthood can reverse the negative impacts of repeated early life maternal separation on behavior and morphology of basolateral amygdala neurons. In this thesis, rat pups were exposed to concomitant maternal separation stress and enriched environment during early life (P2-P21) and their stress-response and behavior were yested during adulthood. Changes in neuronal morphology using Golgi staining was analyzed. Protein regulation of GR, BDNF and p-MAPK in the basolateral amygdala (BLA) using western blot and immunostaining was also examined. Through the above series of experiments, it was demonstrated that exposure to early-life enriched environment can ameliorate the effects of maternal separation stress by renormalizing the underlying neurobiological substrate (namely neuronal morphology and protein regulation) as well as physiology and behavior.