Neonatal endotoxin exposure modifies the acoustic startle response and circulating levels of corticosterone in the adult rat but only following acute stress

A variety of early life stressors have consistently been implicated in the development of psychopathology in adulthood. The current study investigates a rarely considered form of early life stress, bacterial infection, for its ability to induce psychopathology-like symptoms in adult rat. Specifically, neonatal rats were exposed to a simulated bacterial infection. In adulthood the acoustic startle response of these animals was evaluated both prior to and following exposure to restraint stress. Our results indicate that animals neonatally exposed to infection exhibit a significantly exaggerated acoustic startle response but only following exposure to stress. Additionally, we observed that adult animals neonatally exposed to infection, exhibited increased production of circulating corticosterone following stress, indicating potentiated hypothalamic pituitary adrenal axis activity as well as altered novelty seeking behaviour and locomotor activity. These results extend upon existing pre-clinical findings that indicate certain stressful early life events can predispose the adult animal to exhibit abnormal behaviour in adulthood.