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Behav Brain Res. 2008 Aug 22;191(2):227-34. doi: 10.1016/j.bbr.2008.03.031. Epub 2008 Apr 1.

Maternal separation and maternal care act independently on the development of HPA responses in male rats.

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  • 1Institute of Animal Sciences, Swiss Federal Institute of Technology (ETH), Schorenstrasse 16, CH-8603 Schwerzenbach, Switzerland. simone.marci@iss.it

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.

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