Maken, D.S.: Central Mechanisms Regulating Pituitary-Adrenal Activity in Infant Guinea Pigs (Cavia porcellus) during Exposure to Psychological Stressors: Independent and Combined Effects of Maternal Separation and Novelty
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Thema: Maken, D.S.: Central Mechanisms Regulating Pituitary-Adrenal Activity in Infant Guinea Pigs (Cavia porcellus) during Exposure to Psychological Stressors: Independent and Combined Effects of Maternal Separation and Novelty 22.12.12 3:07
Maken, Deborah Suzanne: Central Mechanisms Regulating Pituitary-Adrenal Activity in Infant Guinea Pigs (Cavia porcellus) during Exposure to Psychological Stressors: Independent and Combined Effects of Maternal Separation and Novelty. Doctor of Philosophy (PhD), Wright State University, Biomedical Sciences PhD, 2009.
Separation from the maternal attachment figure, particularly when it occurs in a novel or threatening environment, reliably increases pituitary-adrenal activity in a number of species, and is thought to increase later susceptibility to psychopathology in humans. However, little is known about the central mechanisms mediating these effects. Therefore, I investigated cortisol and ACTH levels in plasma, corticotropin-releasing factor (CRF) mRNA expression in the hypothalamic paraventricular nucleus (PVN), and c-Fos activity in a circuit [medial amygdala (MeA)- bed nucleus of the stria terminalus (BNST)] thought to drive pituitary-adrenal activity during exposure to psychological stressors, as well as in the PVN. Measurements were taken in 16 (+/-1)-day-old infant guinea pigs (Cavia porcellus) during maternal separation, exposure to a novel environment, and exposure to both separation and a novel environment. Levels of plasma cortisol and ACTH, and PVN CRF mRNA expression were elevated only when animals were exposed to both separation and novelty. The putative MeA-BNST circuit was activated during exposure to novelty regardless of whether or not the animals were separated, and c-Fos activity in the PVN was elevated during separation regardless of whether infants were in a novel environment. In sum, there were effects due only to separation; others due only to novelty; and some due to both. These results suggest that CRF activity in the PVN can account for changes in pituitary-adrenal activity during separation in a novel environment. Further, it appears that the effect of novelty on the hypothalamus is mediated at least in part by a circuit from MeA to BNST to PVN. However, other factors appear to mediate activation of the PVN during separation from the attachment figure in a familiar environment, and the lack of activation in the PVN when the attachment figure is present in a novel environment.
Maken, D.S.: Central Mechanisms Regulating Pituitary-Adrenal Activity in Infant Guinea Pigs (Cavia porcellus) during Exposure to Psychological Stressors: Independent and Combined Effects of Maternal Separation and Novelty