Interaction with stressed mothers affects corticosterone levels in pups after reunion and impairs the response to dexamethasone in adult mice.
BACKGROUND
Early adverse experiences are preeminent factors for the development of affective disorders. In the present study, we analyzed the effects of different postnatal manipulations applied either on the mother or on the offspring in mice. Maternal behavior and adrenocortical activity of both mothers and offspring at the end of postnatal stress and at adulthood were considered.


METHODS
From postnatal day (PND) 1 to 14 mice underwent 15min of: (a) brief (15min) pups' exposure to clean bedding (CB: clean bedding), (b) mothers' exposure to the odor of a novel male (SM: stressed mother) or (c) mothers' exposure to a clean cage (CSM: control stressed mother), and (d) standard rearing (N-H: non-handled). The behavior of mouse dams during and after stress sessions was analyzed. Serum corticosterone of mothers and pups at the end of the stress session and 30min after reunion was assessed on PND 14. Moreover, anxiety levels and HPA-axis inhibitory feedback in response to dexamethasone administration were evaluated in adult male offspring.


RESULTS
Overall, during the 14 days of treatment CB mothers when reunited with their pups showed higher maternal behavior than other dams. After the last stress (PND 14) SM and CSM maternal corticosterone levels increased as well as those of CB pups. While 30min of mother-infant interaction restored baseline corticosterone levels in SM and CSM mothers and in CB pups, SM and CSM offspring showed a decrease of corticosterone under baseline levels. At adulthood, SM and CSM males did not show the suppressive hormonal response to dexamethasone treatment. Moreover, adult CB and SM male mice displayed decreased anxiety in the open field.


CONCLUSIONS
Maternal psychosocial stress during lactation seems to permanently affect the offspring's HPA functioning. These effects may be dissociated from the behavioral response as suggested by the decrease of anxiety in SM and CB adult mice.
Moles
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Institute of Neuroscience, CNR, Via del Fosso di Fiorano 64, 00137 Roma, Italy.
Sarli
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Bartolomucci
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D'Amato
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D000305:Adrenal Cortex Hormones / Q000097:blood; D000367:Age Factors; D000818:Animals; D000831:Animals, Newborn / Q000097:blood*; D003345:Corticosterone / Q000097:blood*; D003907:Dexamethasone / Q000494:pharmacology; D005260:Female; D005938:Glucocorticoids / Q000494:pharmacology; D007030:Hypothalamo-Hypophyseal System / Q000254:growth & development* / Q000378:metabolism; D008297:Male; D008425:Maternal Behavior / Q000523:psychology*; D008426:Maternal Deprivation; D051379:Mice; D010913:Pituitary-Adrenal System / Q000254:growth & development* / Q000378:metabolism; D012931:Social Environment; D013268:Stimulation, Chemical; D013315:Stress, Psychological / Q000523:psychology*
D000305:Adrenal Cortex Hormones; D005938:Glucocorticoids; D003907:Dexamethasone; D003345:Corticosterone