Journal
HORMONES AND BEHAVIOR
Volume 60, Issue 2, Pages 165-176Publisher
ACADEMIC PRESS INC ELSEVIER SCIENCE
DOI: 10.1016/j.yhbeh.2011.04.003
Keywords
Maternal separation; Corticosterone; ACTH; SHRP; Novelty; Environment; Genotype; Maternal care; Tyrosine hydroxylase; Melanocortin receptor-2
Categories
Funding
- Top Institute Pharmaceutical Sciences [209]
- EU
- NWO
- Marie Curie Foundation
- Netherlands Ministry of Economic Affairs
- Netherlands Ministry of Education, Culture and Science
- Royal Netherlands Academy of Arts and Sciences
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Adrenal corticosterone secretion of newborn mice rapidly desensitizes to repeated maternal absence. The present study investigated the effects of novelty exposure, maternal care and genotype on this phenomenon. Maternal separation (MS) took place on postnatal days (pnd) 3-5. In Wistar rats, the degree of novelty in the MS-environment was varied by exposing pups to: (i) home separation: pups remained in the home cage: (ii) novel separation: pups were placed individually in a novel cage. Maternal care was recorded on pnd 1 to 4. To investigate the effect of genotype, we also examined Long Evans in the home separation condition. Basal and stress-induced ACTH and corticosterone levels were measured. Adrenal tyrosine hydroxylase (TH) and melanocortin receptor-2 (MCR-2) proteins served as markers for adrenal function. We show, in both rat strains, that the rise in plasma corticosterone induced by a single 8 h-MS on pnd 5 was abolished, when this separation procedure had also been performed on pnd 3 and 4. Habituation to maternal absence occurred irrespective of housing conditions. However, pups in the home separation condition received less maternal care upon reunion than those placed in the novel separation. These home separation pups appeared more responsive to a subsequent acute novelty-stressor, and their adrenal TH and MCR-2 were higher. Long Evans rats appeared more stress responsive than the Wistars, in the home separation condition. In conclusion, separation environment, maternal care and genotype do not affect adrenal desensitization to repeated 8 h-MS itself, but may modulate the adrenal stress-responsiveness of separated pups. (C) 2011 Elsevier Inc. All rights reserved.
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