| Abstract No.: | A-E1169 |
| Country: | Canada |
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| Title: | THE EFFECTS OF NATURAL VARIATIONS IN MATERNAL CARE ON THE CIRCADIAN CLOCK PROTEIN PERIOD2 |
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| Authors/Affiliations: | 2 Sabine Dhir*; 1 Shakti Sharma; 1 Josie Diorio; 2 Michael J. Meaney;
1 Douglas Hospital Research Center; 2 McGill University, Douglas Hospital Research Center, Montreal, QC, Canada
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| Content: | Background: Variations in levels of maternal care during the immediate postpartum period exert enduring influences on the stress and neuroendocrine development of offspring of high and low licking and grooming (LG) rats. As adults, the offspring of female rats that receive lower levels of LG in the first week of life display lower levels of glucocorticoid receptors (GR) in the hippocampus when compared to offspring of female rats who display higher levels of licking. Moreover, in response to tests of both restraint stress and chronic stress, the offspring of Low LG rats exhibit higher levels of hypothalamic-pituitary-adrenal axis (HPA) activity when compared to offspring of High LG mothers (Liu et al., 1997). Previously, we have found that Low LG male offspring display significantly higher basal levels of both corticosterone and ACTH two hours before lights off and at least an hour into the dark phase which also peak at least three hours earlier when compared to High LG offspring (Dhir et al., 2006). This indicates that the basal glucocorticoid/HPA pattern in these two phenotypes is dissimilar in excretion and amplitude. In the brain and in peripheral tissues throughout the body, glucocorticoids play a key role in the regulation of circadian clock genes which allow for the timing and coordination of many key events and daily occurrences (Balsalobre et al., 2000, Dickmeis et al., 2007). Objectives: In this study we aimed to investigate the effect of natural variations in maternal care on basal glucocorticoid levels and the circadian clock protein Period2 (Per2) in both the brain and periphery. Materials & Methods: Male offspring of High and Low LG dams were sacrificed at six time points across a 24 hour period to provide a daily profile of Per2 activity via immunohistochemistry and immunoblot in the brain and periphery. Adrenalectomy surgeries (ADX) were also performed at two key time points (ZT10 and ZT13) in male offspring and brain sections were analyzed for Per2. Results: In both the central nucleus of the amygdala (CEA) and in the oval nucleus of the bed nucleus of the stria terminalis (BNSTov) the offspring of High LG rats have significantly lower levels of Per2 compared to Low LG offspring at ZT10. In the suprachiasmatic nucleus (SCN), High LG offspring have significantly higher levels of Per2 immunoreactivity (IR) compared with the offspring of Low LG dams. In the liver, higher levels of Per2 IR are expressed in the Low LG offspring compared to the High offspring at ZT 7 and 16. ADX significantly blunted Per2 IR in the CEA and BNSTov at ZT10 with no significant ADX effect in the SCN. Conclusion: These results suggest that maternal LG may act as an environmental signal through the circadian system to potentially modulate adaptability of an organism to its surroundings. |
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