This Article Full Text (PDF) References 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 Web of Science Similar articles in PubMed Alert me to new issues of the journal Add to Saved Citations Download to citation manager Request Permissions Request Reprints Add to My Marked Citations Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Citing Articles via Scopus Google Scholar Articles by Liu, T. Articles by Borjigin, J. Search for Related Content PubMed PubMed Citation Articles by Liu, T. Articles by Borjigin, J. Pubmed/NCBI databases Compound via MeSH Substance via MeSH Social Bookmarking                         What's this?

Free-Running Rhythms of Pineal Circadian Output

Department of Molecular and Integrative Physiology, University of Michigan Medical School, Ann Arbor

Jimo Borjigin

Department of Molecular and Integrative Physiology, University of Michigan Medical School, Ann Arbor, borjigin{at}umich.edu

Circadian rhythms are self-sustaining oscillations that free-run in constant conditions with a period close to 24 h. Overt circadian rhythms have been studied mostly using onset phase as the marker for the underlying pacemaker. Using in vivo online pineal microdialysis, the authors have performed detailed analysis of free-running profiles of rat pineal secretory products, including N-acetylserotonin (NAS) and melatonin that have precisely defined onsets and offsets. When rats entrained in LD 12:12 were released into constant darkness (DD), both onset and offset phases of melatonin and NAS free-run. However, while onsets free-run with a period closer to a day (FRP^on = 24-24.17 h) at the beginning, offset phases free-run with significantly larger FRPs (free-running periods) (FRP^off = 24.24-24.42 h). This asymmetric free-running of onset and offset of NAS and melatonin in DD resulted in a 60- to 120-min increase of secretion duration of both NAS and melatonin. The rate of expansion of melatonin duration was 10 to 15 min per circadian cycle. The expansion of melatonin secretion duration ended for some within 4 days, while others were still expanding by the end of 10th day in DD. These results revealed that upon release into DD, the pacemaker’s oscillation is initially driven by 2 forces, free running and decompression, before reaching a stable state of free running, and suggest that the circadian pacemaker may be an elastic structure that can decompress and compress under varying photic conditions. They also illustrate the importance of using both onset and offset of a given rhythm as phase markers, as compression/decompression, and transient disparity between FRP^on and FRP^off may be a common phenomenon of the circadian pacemaker.

Key Words: pineal gland • melatonin • pineal microdialysis • free-running period • circadian rhythms • constant dark • aftereffects • decompression

Journal of Biological Rhythms, Vol. 20, No. 5, 430-440 (2005)
DOI: 10.1177/0748730405277868


CiteULike    Complore    Connotea    Del.icio.us    Digg    Reddit    Technorati    Twitter    What's this?

This article has been cited by other articles:

				M. D. Schwartz, C. Wotus, T. Liu, W. O. Friesen, J. Borjigin, G. A. Oda, and H. O. de la Iglesia Dissociation of circadian and light inhibition of melatonin release through forced desynchronization in the rat PNAS, October 13, 2009; 106(41): 17540 - 17545. [Abstract] [Full Text] [PDF]