BDNF Knockdown in the VTA Blocks Social Stress‐Induced Deficits in Social Behavior and Nucleus Accumbens ΔFosB Expression

Abstract

Social defeat stress, a salient stressor that translates readily from animal studies to humans, alters social approach behavior and induces brain‐derived neurotrophic factor (BDNF) in the ventral tegmental area (VTA), as well as the stable transcription factor, ΔFosB, in the nucleus accumbens (NAc) of rats. However, it is unknown whether VTA BDNF is required for these effects of stress. Rats underwent stereotaxic surgery to receive bilateral intra‐VTA infusions of adeno‐associated virus inducing green fluorescent protein (AAV‐GFP) or GFP and short hairpin RNA directed against BDNF (shRNA‐BDNF). Following recovery, rats were subjected to control handling or social defeat stress, consisting of a brief confrontation between an aggressive resident and an experimental intruder rat every third day for 10 days. Social interaction was assessed in a social approach assay two weeks later. Following perfusion, brains were removed and processed for immunohistochemical analysis of ΔFosB expression. VTA BDNF knockdown attenuated the effect of social stress on weight gain, and increased social approach behavior, which is normally reduced by social stress. Furthermore, social stress increased NAc ΔFosB labeling in AAV‐GFP rats, but this effect was blocked by prior shRNA‐BDNF treatment. This study further implicates VTA BDNF signaling in the effects of stress on social behavior. VTA BDNF appears to be required for the long‐lasting effects of social stress on ΔFosB expression in the NAc. Thus, activation of BDNF signaling in mesolimbic circuits may underlie the persistent deficits of social behavior induced by stress exposure in some individuals.