Stress hormone exposure induces anhedonic-like behavior in adult male rats but not in adolescent rats. (2016)

Undergraduates: Brayden Fortino, Verda Agan Anel Jaramillo Joyce Besheer

Faculty Advisor: Joyce Besheer
Department: Psychology & Neuroscience

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Stress has been shown to be a major predictor in the onset of various neuropsychological disorders including major depressive disorder (MDD). A core symptom of MDD is anhedonia or a loss of interest/pleasure in normally rewarding activities. However little is known about how stress exposure during the adolescent developmental period affects the emergence of anhedonia and how this differs from stress exposure in adulthood. Using an animal model we have previously shown anhedonic-like behavior in adult rats following chronic exposure to the stress hormone corticosterone (CORT). Thus the aim of this work is to explore the relationship between CORT exposure and anhedonic-like behavior as measured by sucrose intake tests in adolescent and adult male rats. Adolescent (PND 28) and adult (PND 70) rats were exposed to CORT (0.3 mgs/ml) for 21 days. Sucrose intake tests were conducted weekly to measure anhedonic-like behavior. Here we show that chronic CORT exposure does indeed predict a significant decrease in sucrose intake in adult male rats; however, this effect was not observed in adolescent male rats. These results suggest that there are underlying molecular mechanisms occurring within adolescent male rats protecting them from the effects of CORT exposure on anhedonic-like behavior. Additional analysis of Arc expression-an immediate early gene and marker for neural plasticity-were conducted to identify the underlying molecular mechanisms of this effect.