Early maternal deprivation in rats: a proposed animal model for the study of developmental neuroimmunoendocrine interactions

Adult animals that had been subjected to a single prolonged episode of maternal deprivation (MD) [24 h, postnatal day (PND) 9-10] show long-term behavioral alterations that resemble specific symptoms of schizophrenia. Moreover, at adolescence MD rats showed depressive-like behavior and altered motor responses. According to the neurodevelopmental hypothesis, certain behavioral abnormalities observed in MD animals may be related to altered neurodevelopmental processes triggered by MD-induced elevated glucocorticoids in relevant specific brain regions. We review here these neuroendocrine effects and show new data indicating that the MD procedure induces diverse detrimental effects on the immune system that are already revealed in the short term (PND 13) and persist into adulthood. These long-lasting effects might be related to altered hypothalamus-pituitary-adrenal axis activity and to social as well as nutrition-related factors. In fact, MD induces long-lasting decreases in body weight. In view of our findings we propose the present MD procedure as a potentially useful model to analyze developmental interactions between early psychophysiological stress and immunodeficient states.