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Ultradian corticosterone secretion is maintained in the absence of circadian cues
Author(s) -
Waite Eleanor J.,
McKenna Mervyn,
Kershaw Yvonne,
Walker Jamie J.,
Cho Kwangwook,
Piggins Hugh D.,
Lightman Stafford L.
Publication year - 2012
Publication title -
european journal of neuroscience
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.346
H-Index - 206
eISSN - 1460-9568
pISSN - 0953-816X
DOI - 10.1111/j.1460-9568.2012.08213.x
Subject(s) - ultradian rhythm , circadian rhythm , endocrinology , medicine , corticosterone , pulsatile flow , suprachiasmatic nucleus , biology , light effects on circadian rhythm , hypothalamus , hormone
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.