Early life stress and the embryonic social brain.

Early life stress is often associated with negative consequences, but recent studies suggest stress in early life can also have adaptive effects. Stress may serve as a signal of adverse conditions, triggering developmental changes to prepare an individual for the future in accordance with the environmental matching hypothesis. We know little about how stress affects the brain regions regulating social behaviour, but since early life stress can have an adaptive effect on social behaviour, we expect it to impact on the neural circuits that regulate these behaviours. Here we investigated the effects of prenatal stress on mesotocin in the avian ‘social brain’. We used a late stage quail embryo model to investigate the short term consequences of prenatal stress and explore how the avian social brain is ‘set-up’ for post-hatch life. We manipulated stress by injecting corticosterone, the avian stress hormone, into incubating Japanese quail eggs (both sexes) and collected brains onto dry ice the day before hatch. Corticosterone injection in ovo is biologically relevant and avoids any maternal influence confounds. The nonapeptide mesotocin is associated with social behaviour, so we quantified mesotocin mRNA using in situ hybridization in brain regions, specifically the bed nucleus of the stria terminalis (Bnst) and the paraventricular nucleus. Initial analyses show no significant differences in mesotocin mRNA expression in the Bnst of prenatally stressed embryos compared to controls. Additional studies on the effects of early life stress on social behaviour at different sensitive developmental time points are required to help us determine when modifications to social behaviour occur, and whether these changes in behaviour correspond to changes in the mesotocin system and other social brain circuitry.