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Ultradian corticosterone secretion is maintained in the absence of circadian cues.

Authors
  • Waite, Eleanor J1
  • McKenna, Mervyn
  • Kershaw, Yvonne
  • Walker, Jamie J
  • Cho, Kwangwook
  • Piggins, Hugh D
  • Lightman, Stafford L
  • 1 Henry Wellcome Laboratories for Integrative Neuroscience and Endocrinology, University of Bristol, Dorothy Hodgkin Building, Whitson Street, Bristol BS1 3NY, UK. [email protected]
Type
Published Article
Journal
European Journal of Neuroscience
Publisher
Wiley (Blackwell Publishing)
Publication Date
Oct 01, 2012
Volume
36
Issue
8
Pages
3142–3150
Identifiers
DOI: 10.1111/j.1460-9568.2012.08213.x
PMID: 22823558
Source
Medline
License
Unknown

Abstract

Plasma levels of corticosterone exhibit both circadian and ultradian rhythms. The circadian component of these rhythms is regulated by the suprachiasmatic nucleus (SCN). Our studies investigate the importance of the SCN in regulating ultradian rhythmicity. Two approaches were used to dissociate the hypothalamic-pituitary-adrenal (HPA) axis from normal circadian input in rats: (i) exposure to a constant light (LL) environment and (ii) electrolytic lesioning of the SCN. Blood was sampled using an automated sampling system. As expected, both treatments resulted in a loss of the circadian pattern of corticosterone secretion. Ultradian pulsatile secretion of corticosterone however, was maintained across the 24 h in all animals. Furthermore, the loss of SCN input revealed an underlying relationship between locomotor and HPA activity. In control (LD) rats there was no clear correlation between ultradian locomotor activity and hormone secretion, whereas, in LL rats, episodes of ultradian activity were consistently followed by periods of increased pulsatile hormone secretion. These data clearly demonstrate that the ultradian rhythm of corticosterone secretion is generated through a mechanism independent of the SCN input, supporting recent evidence for a sub-hypothalamic pulse generator.

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