This Article Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Copyright Permission Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Girotti, M. Articles by Spencer, R. L. Search for Related Content PubMed PubMed Citation Articles by Girotti, M. Articles by Spencer, R. L.

Differential Responses of Hypothalamus-Pituitary-Adrenal Axis Immediate Early Genes to Corticosterone and Circadian Drive

Division of Behavioral Neuroscience, Department of Psychology, University of Colorado, Boulder, Colorado 80309

Address all correspondence and requests for reprints to: Dr. M. Girotti, Department of Psychology, Muenzinger Building Room D244, University of Colorado, UCB 345, Boulder, Colorado 80309. E-mail: girotti{at}colorado.edu.

The hypothalamus-pituitary-adrenal (HPA) axis diurnal cycle of activity is manifest in circadian rhythms of ACTH and corticosterone secretion, which in the rat peak around the onset of the dark period. This cycle is thought to be driven by daily fluctuations in activity of CRH neurons within the paraventricular nucleus of the hypothalamus (PVN), controlled by suprachiasmatic nucleus inputs. In this study we examined whether the circadian drive that regulates ACTH and corticosterone basal secretion in the rat is reflected in PVN immediate early gene expression and, if so, whether different genes respond uniformly or uniquely to circadian stimulatory input. In addition, we examined how circadian drive and acute stress, two categories of stimuli that induce HPA axis activation, comparatively affect gene expression within different components of the HPA axis (c-fos mRNA, CRH heteronuclear RNA, and zif268 mRNA in PVN; c-fos mRNA, proopiomelanocortin heteronuclear RNA, and zinc finger 268 mRNA in anterior pituitary; c-fos mRNA and nerve growth factor I-B mRNA in adrenal cortex). Finally, we examined whether circadian differences in gene expression depend on endogenous glucocorticoids and, if so, whether the dependence is on an acute or permissive influence of the hormone. We found that a circadian drive that regulates HPA axis basal hormone secretion is also manifest on basal c-fos gene expression in the PVN. Moreover, we show that different immediate early genes within the HPA axis anatomical components display different diurnal patterns of gene expression. These differential patterns result, in part, from gene-specific responses to circadian signals and acute and/or permissive glucocorticoid actions.

This article has been cited by other articles:

				M. Girotti, M. S. Weinberg, and R. L. Spencer Diurnal expression of functional and clock-related genes throughout the rat HPA axis: system-wide shifts in response to a restricted feeding schedule Am J Physiol Endocrinol Metab, April 1, 2009; 296(4): E888 - E897. [Abstract] [Full Text] [PDF]

				A. Kapoor and S. G. Matthews Prenatal Stress Modifies Behavior and Hypothalamic-Pituitary-Adrenal Function in Female Guinea Pig Offspring: Effects of Timing of Prenatal Stress and Stage of Reproductive Cycle Endocrinology, December 1, 2008; 149(12): 6406 - 6415. [Abstract] [Full Text] [PDF]