ORIGINAL

Abstract

In humans, adversity faced during youth is commonly known to increase the risk of psychiatric disorders such as anxiety disorders, major depressive disorder, and attention deficit hyperactivity disorder (ADHD) in adulthood. In an effort to determine how these damaging effects can be mitigated, there is a pressing need to understand the neuronal mechanisms underlying these behavioral effects. Previous studies have established how early life adversity (ELA) in rodents can lead to increased avoidance behavior as well as hyperactivity in adulthood. Studies have suggested that ELA may exert its actions on the brain by interfering with developmental trajectories. However, the emergence of differences in defensive behaviors and associated neuronal changes due to ELA have yet to be elucidated in the early stages of development. This project characterized behavioral differences between control and ELA mice across development from P16 to P45 and also searched for changes to the neuronal substrates in the brain regions involved in stress and threat responses, such as the dentate gyrus (DG), ventral hippocampus (vHIP), and the basolateral amygdala (BLA). While increased avoidance behavior did not emerge until the mice were fully adults, hyperactivity was present in ELA males at P25 and P45 during aversive tests, and ELA males at P16 had a larger percentage of PV\(^{+}\) and PNN colocalized cells in the vDG than the control males.