Skip to main content
Article thumbnail
Location of Repository

Diurnal expression of functional and clock-related genes throughout the rat HPA axis: system-wide shifts in response to a restricted feeding schedule

By Milena Girotti, Marc S. Weinberg and Robert L. Spencer

Abstract

The diurnal rhythm of glucocorticoid secretion depends on the suprachiasmatic (SCN) and dorsomedial (putative food-entrainable oscillator; FEO) nuclei of the hypothalamus, two brain regions critical for coordination of physiological responses to photoperiod and feeding cues, respectively. In both cases, time keeping relies upon diurnal oscillations in clock gene (per1, per2, and bmal) expression. Glucocorticoids may play a key role in synchronization of the rest of the body to photoperiod and food availability. Thus glucocorticoid secretion may be both a target and an important effector of SCN and FEO output. Remarkably little, however, is known about the functional diurnal rhythms of the individual components of the hypothalamic-pituitary-adrenal (HPA) axis. We examined the 24-h pattern of hormonal secretion (ACTH and corticosterone), functional gene expression (c-fos, crh, pomc, star), and clock gene expression (per1, per2 and bmal) in each compartment of the HPA axis under a 12:12-h light-dark cycle and compared with relevant SCN gene expression. We found that each anatomic component of the HPA axis has a unique circadian signature of functional and clock gene expression. We then tested the susceptibility of these measures to nonphotic entrainment cues by restricting food availability to only a portion of the light phase of a 12:12-h light-dark cycle. Restricted feeding is a strong zeitgeber that can dramatically alter functional and clock gene expression at all levels of the HPA axis, despite ongoing photoperiod cues and only minor changes in SCN clock gene expression. Thus the HPA axis may be an important mediator of the body entrainment to the FEO

Topics: Articles
Publisher: American Physiological Society
OAI identifier: oai:pubmedcentral.nih.gov:2670633
Provided by: PubMed Central
Download PDF:
Sorry, we are unable to provide the full text but you may find it at the following location(s):
  • http://www.pubmedcentral.nih.g... (external link)
  • Suggested articles


    To submit an update or takedown request for this paper, please submit an Update/Correction/Removal Request.