Paternal Aggression in Early-Life Impairs the Spatial Memory and Passive Avoidance Learning in Adulthood of Male Rats: The Possible Role of DRD2

Abstract

Negative early-life experiences (e.g., having an aggressive father) can leave long-lasting impacts on the behavior. However, it is not clear if they influence learning and memory. In this study, we investigated the influences that the presence of an aggressive father had on the level of passive avoidance learning and spatial memory. We also studied the changes in the dopamine receptor D2 (DRD2) and peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α) gene expression in the hippocampus. Then, we evaluated if a DRD2 antagonist (Sulpiride, 0.125, 0.25, or 0.5 µg/rat) could modulate these changes. We found that the subjects exposed to early-life stress made by aggressive fathers had impaired passive avoidance learning and spatial memory than those with normal fathers. Treatment with Sulpiride improved passive avoidance learning and spatial memory in rats with aggressive fathers. The rats with aggressive fathers also had higher expression of the DRD2 gene in their hippocampus than those with normal fathers, while the PGC-1α gene expression was not different among groups. Treatment with Sulpiride (0.125, 0.25, or 0.5 µg/rat) reduced the DRD2 gene expression in those with aggressive fathers to the normal level in those with normal fathers. These data suggest that living in a shared place with an aggressive father, even without any physical contact, can detrimentally affect passive avoidance learning and spatial memory which is accompanied by the increased expression of the DRD2 gene. Also, Sulpiride as a dopaminergic antagonist could reverse this process.