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In adult animals, the consequences of stress are often severe and long lasting. Repeated subjugation in adult male golden hamsters inhibits aggression and increases submissive and avoidant behaviours. By contrast, subjugation during puberty enhances offensive aggression. The goals of this study were to characterize behavioural and neuroendocrine responses of naïve and repeatedly subjugated juveniles to social defeat and to assess potential recovery from social stress. From the onset of puberty on postnatal day 28 (P28) to mid puberty (P42), animals were either socially subjugated or placed in a clean and empty cage for 20 min daily. The subjugated and control groups were further divided into subgroups and sacrificed under basal conditions or after social defeat on P28, P35 (early puberty), P45 (mid puberty) and P70 (early adulthood). On P35 and P45, repeatedly subjugated juveniles showed a complete inhibition of olfactory investigation (i.e. risk assessment) towards aggressive adults. Repeatedly subjugated also animals had lower postdefeat cortisol levels than controls on P45. Interestingly, basal cortisol levels increased gradually during puberty but did not differ between treatment groups at any point. Repeated subjugation was also associated with increased tyrosine hydroxylase immunoreactivity (ir-TH) within the extended medial amygdala. After a 4-week recovery period, none of these variables differed between subjugated and control groups. In an additional experiment, subjugated adults also had increased ir-TH in the medial extended amygdala, suggesting that these neurones are particularly responsive to social stress. In conclusion, puberty may be a developmental period characterized by behavioural and neuroendocrine plasticity in stress responsiveness. Furthermore, peri-pubertal changes in stress hormones may explain why juvenile hamsters are more resilient to social stress than adults.

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We examined the effects of acculturation, depressive symptoms, progesterone, and estriol (E3) as predictors of preterm birth (PTB) in pregnant Hispanic women. This cross-sectional study recruited a sample of 470 Hispanic women between 22- and 24-week gestation from physician practices and community clinics. We used the CES-D to measure maternal depressive symptoms. We measured acculturation by English proficiency on the Bidimensional Acculturation Scale, residence index by years in the USA minus age, nativity, and generational status. Serum progesterone and E3 were analyzed by EIA. Ultrasound and medical records determined gestational age after delivery. In χ2 analysis, there were a significantly greater percentage of women with higher depressive scores if they were born in the USA. In a structural equation model (SEM), acculturation (English proficiency, residence index, and generational status) predicted the estriol/progesterone ratio (E/P), and the interaction of depressive symptoms with the E/P ratio predicted PTB. Undiagnosed depressive symptoms during pregnancy may have biological consequences increasing the risk for PTB.