Long-term consequences of early maternal deprivation in serotonergic activity and HPA function in adult rat

Increasing body of evidence indicates that early life stressful events may induce permanent alterations in neurodevelopment, which in turn, could lead to the development of psychopathologies in adulthood. In particular, maternal deprivation (MD) for 24h in rats has been associated with several abnormalities in brain and behaviour during adulthood, relevant to the neurobiological substrate of anxiety disorders. The aim of the present study was to clarify the long-term effects of MD, on hypothalamo-pituitary-adrenal (HPA) axis activity and serotonergic (5-HT) function, in adulthood, subjects that have not been yet thoroughly investigated. For this purpose, Wistar rat pups were deprived from their mothers for a 24-h single period at postnatal day 9 (pnd 9) and were examined when aged 69-90 days. Plasma corticosterone and ACTH levels along with the animal's behaviour in an open field were used as indices of stress. Moreover, serotonergic activity was estimated in hypothalamus and hippocampus, key structures in the coordination of neuroendocrine and behavioural responses to stress. Interestingly, in adulthood, MD rats compared to controls, displayed decreased body weight, increased serotonergic activity and "anxiety" related behaviour, as well as elevated plasma corticosterone and ACTH levels. The findings of this study showed that MD results in long-term modifications in HPA axis and serotonergic activity indicating a clear relationship between early life stressful events and the development of anxiety-like disorders later in adulthood.