|
Sign In to gain access to subscriptions and/or personal tools.
|
Getting Through to Circadian Oscillators: Why Use Constant Routines?
Jeanne F. Duffy
Division of Sleep Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115, USA
Derk-Jan Dijk
Centre for Chronobiology, School of Biomedical and Life Sciences, University of Surrey, Guildford GU2 7XH, UK
Overt 24-h rhythmicity is composed of both exogenous and endogenous components, reflecting the product of multiple (periodic) feedback loops with a core pacemaker at their center. Researchers attempting to reveal the endogenous circadian (near 24-h) component of rhythms commonly conduct their experiments under constant environmental conditions. However, even under constant environmental conditions, rhythmic changes in behavior, such as food intake or the sleep-wake cycle, can contribute to observed rhythmicity in many physiological and endocrine variables. Assessment of characteristics of the core circadian pacemaker and its direct contribution to rhythmicity in different variables, including rhythmicity in gene expression, may be more reliable when such periodic behaviors are eliminated or kept constant across all circadian phases. This is relevant for the assessment of the status of the circadian pacemaker in situations in which the sleep-wake cycle or food intake regimes are altered because of external conditions, such as in shift work or jet lag. It is also relevant for situations in which differences in overt rhythmicity could be due to changes in either sleep oscillatory processes or circadian rhythmicity, such as advanced or delayed sleep phase syndromes, in aging, or in particular clinical conditions. Researchers studying human circadian rhythms have developed constant routine protocols to assess the status of the circadian pacemaker in constant behavioral and environmental conditions, whereas this technique is often thought to be unnecessary in the study of animal rhythms. In this short review, the authors summarize constant routine methodology and what has been learned from constant routines and argue that animal and human circadian rhythm researchers should (continue to) use constant routines as a step on the road to getting through to central and peripheral circadian oscillators in the intact organism.
Key Words: chronobiology • sleep • melatonin • temperature • masking
Journal of Biological Rhythms, Vol. 17, No. 1,
4-13 (2002)
DOI: 10.1177/074873002129002294
 CiteULike  Complore  Connotea  Del.icio.us  Digg  Reddit  Technorati  Twitter What's this?
This article has been cited by other articles:
|
|
|
|
 
S. Vollenweider, A. Wirz-Justice, J. Flammer, S. Orgul, and K. Krauchi
Chronobiological characterization of women with primary vasospastic syndrome: body heat loss capacity in relation to sleep initiation and phase of entrainment
Am J Physiol Regulatory Integrative Comp Physiol,
February 1, 2008;
294(2):
R630 - R638.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
C. Gronfier, K. P. Wright Jr., R. E. Kronauer, and C. A. Czeisler
Entrainment of the human circadian pacemaker to longer-than-24-h days
PNAS,
May 22, 2007;
104(21):
9081 - 9086.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
C. E. Kline, J. L. Durstine, J. M. Davis, T. A. Moore, T. M. Devlin, M. R. Zielinski, and S. D. Youngstedt
Circadian variation in swim performance
J Appl Physiol,
February 1, 2007;
102(2):
641 - 649.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
J. Arendt
Melatonin: Characteristics, Concerns, and Prospects
J Biol Rhythms,
August 1, 2005;
20(4):
291 - 303.
[Abstract]
[PDF]
|
|
|
|
|
|
|
S. M. W Rajaratnam, B. Middleton, B. M Stone, J. Arendt, and D.-J. Dijk
Melatonin advances the circadian timing of EEG sleep and directly facilitates sleep without altering its duration in extended sleep opportunities in humans
J. Physiol.,
November 15, 2004;
561(1):
339 - 351.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
C. Gronfier, K. P. Wright Jr., R. E. Kronauer, M. E. Jewett, and C. A. Czeisler
Efficacy of a single sequence of intermittent bright light pulses for delaying circadian phase in humans
Am J Physiol Endocrinol Metab,
July 1, 2004;
287(1):
E174 - E181.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
V. Mongrain, S. Lavoie, B. Selmaoui, J. Paquet, and M. Dumont
Phase Relationships between Sleep-Wake Cycle and Underlying Circadian Rhythms in Morningness-Eveningness
J Biol Rhythms,
June 1, 2004;
19(3):
248 - 257.
[Abstract]
[PDF]
|
|
|
|
|
|
|
S. M. W. Rajaratnam, D.-J. Dijk, B. Middleton, B. M. Stone, and J. Arendt
Melatonin Phase-Shifts Human Circadian Rhythms with No Evidence of Changes in the Duration of Endogenous Melatonin Secretion or the 24-Hour Production of Reproductive Hormones
J. Clin. Endocrinol. Metab.,
September 1, 2003;
88(9):
4303 - 4309.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
S. B. S Khalsa, M. E Jewett, C. Cajochen, and C. A Czeisler
A phase response curve to single bright light pulses in human subjects
J. Physiol.,
June 15, 2003;
549(3):
945 - 952.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
S. Mahamed, D. A Cunningham, and J. Duffin
Changes in respiratory control after three hours of isocapnic hypoxia in humans
J. Physiol.,
February 15, 2003;
547(1):
271 - 281.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
D. Aeschbach, L. Sher, T. T. Postolache, J. R. Matthews, M. A. Jackson, and T. A. Wehr
A Longer Biological Night in Long Sleepers Than in Short Sleepers
J. Clin. Endocrinol. Metab.,
January 1, 2003;
88(1):
26 - 30.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
E. B. Klerman, T. L. Shanahan, D. J. Brotman, D. W. Rimmer, J. S. Emens, J. F. Rizzo III, and C. A. Czeisler
Photic Resetting of the Human Circadian Pacemaker in the Absence of Conscious Vision
J Biol Rhythms,
December 1, 2002;
17(6):
548 - 555.
[Abstract]
[PDF]
|
|
|
|
|
