Stress hormones and emotion-regulation in two genetic animal models of depression

Children of depressed parents often exhibit emotion-regulation deficits, characterized by either excessive withdrawal or approach strategies toward the mother. The current study examined behavioral and physiological emotion-regulation in preweanling pups (postnatal day 17-19) belonging to two different genetic animal models of depression, Wistar-Kyoto (WKY) and Flinders Sensitive-Line (FSL) rats. The study also examined the effects of stress on the two animal models, hypothesizing an interactive effect of hereditary vulnerability and exposure to stress. Chronic-stress was simulated by providing limited bedding to the dam and litter for a week, in the early postnatal period. Acute-stress was generated by exposure to an adult mate rat, an ethologically valid stressor. Emotion - regulation of the pups was examined using a Y-maze preference test and radioimmunoassay of Hypothalamic-Pituitary-Ad renal (HPA) axis hormones (corticosterone Et adrenocorticotropin/ACTH). WKY and FSL pups exhibited reduced approach-behavior toward the dam, an emotion-regulation profile reminiscent of avoidant attachment evident in many children of depressed parents. In contrast, the two animal models did not show similar HPA axis activity. FSL pups exhibited markedly lower ACTH levels compared to controls, while WKY pups did not differ from controls. With regard to the stress manipulations, the limited-bedding condition had no effect, white the acute-stressor induced overall effects on all groups, with more pronounced