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In 2011, the U.S. reported 3 million child maltreatment cases, an uncomfortably high but recurring figure each year. Research shows exposure to early life stress (ELS) increases an individual’s susceptibility to substance abuse, specifically of nicotine, alcohol, and cocaine. Increased susceptibility may result from dysregulation of the HPA axis sustaining activation into adulthood after ELS. Hyperactivation of the HPA axis significantly reduces hippocampal BDNF, a neurotrophin involved in neuronal growth and plasticity. Reduced hippocampal BDNF may be a factor in substance abuse vulnerability. Additionally, research shows exercise protects hippocampal BDNF from stress induced down-regulation. To explore these relationships, this study used maternal separation (MS) to model ELS in rats. Following MS, rats voluntarily exercised for three weeks, or were sedentary, followed by cocaine conditioned place preference. We quantified hippocampal BDNF from these groups and predicted MS would down-regulate BDNF and exercise would ameliorate this effect. Finally, we predicted BDNF levels would correlate with total running activity. We found no significant effect of MS or exercise, and total running activity weakly correlated with BDNF expression. Our results parallel the behavioral results of this experiment, in which there also were no significant effects of exercise on sensitivity to the locomotor or rewarding effects of cocaine. Thus, although no significance was found in this study, it may provide further insight into the relationships between ELS, exercise, and substance abuse and provide footing for improvement in the development of designs exploring them.


BDNF; Brain-derived neurotrophic factor; Child abuse; Cocaine; Drug abuse; Early life stress; Exercise; Growth factors; Hippocampus (Brain); Neurotropin; Substance abuse


Developmental Psychology




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