title: Maternal separation and maternal care act independently on the development of HPA responses in male rats.
abstract: Postnatal manipulations such as brief (early handling, EH) and long, daily mother-offspring separations (maternal separation, MS) in rats are used to study the mechanisms underlying developmental plasticity of stress and fear responses, and to model stress-related disorders in humans and in non-human animals. Current evidence suggests that, compared to non-handled rats, EH reduces hypothalamic-pituitary-adrenal (HPA) reactivity in the adult offspring through stimulating increased levels of active maternal care. In contrast, despite a similar increase in active maternal care, MS does not reduce HPA reactivity, thus suggesting that long mother-offspring separations may counteract the effects of increased active maternal care. We therefore attempted to selectively manipulate levels of active maternal care and durations of mother-offspring separations in neonate rats. Rat pups were exposed to different combinations of EH and MS from postnatal day (PND) 2 to 10 using a split-litter design. Maternal behaviour was recorded from PND 2 to 8 and behavioural and endocrine responses to stress were studied in adult male offspring. Low levels of maternal care combined with long mother-offspring separations increased HPA-reactivity compared to both high maternal care combined with long mother-offspring separations and low maternal care combined with brief separations. These findings further support the hypothesis that active maternal care and long mother-offspring separation act independently, and exert opposing effects, on adult offspring's HPA responses, but that increased maternal care may buffer the adverse consequences of long separations.
authors.affiliation: Institute of Animal Sciences, Swiss Federal Institute of Technology (ETH), Schorenstrasse 16, CH-8603 Schwerzenbach, Switzerland. simone.marci@iss.it
authors.forename: Simone
authors.initials: S
authors.lastname: Macrì
authors.forename: Flavia
authors.initials: F
authors.lastname: Chiarotti
authors.forename: Hanno
authors.initials: H
authors.lastname: Würbel
mesh_terms: D000324:Adrenocorticotropic Hormone / Q000097:blood; D000704:Analysis of Variance; D000818:Animals; D000831:Animals, Newborn; D019540:Area Under Curve; D001522:Behavior, Animal; D003345:Corticosterone / Q000097:blood; D005106:Exploratory Behavior / Q000502:physiology; D005260:Female; D007030:Hypothalamo-Hypophyseal System / Q000254:growth & development*; D008297:Male; D008425:Maternal Behavior; D008426:Maternal Deprivation; D010913:Pituitary-Adrenal System / Q000254:growth & development*; D011247:Pregnancy; D051381:Rats; D012149:Restraint, Physical / Q000379:methods; D012737:Sex Factors
chemical_list: D000324:Adrenocorticotropic Hormone; D003345:Corticosterone