Document Detail

Redefining the limits of day length responsiveness in a seasonal mammal.
MedLine Citation:
PMID:  17901234     Owner:  NLM     Status:  MEDLINE    
At temperate latitudes, increases in day length in the spring promote the summer phenotype. In mammals, this long-day response is mediated by decreasing nightly duration of melatonin secretion by the pineal gland. This affects adenylate cyclase signal transduction and clock gene expression in melatonin-responsive cells in the pars tuberalis of the pituitary, which control seasonal prolactin secretion. To define the photoperiodic limits of the mammalian long day response, we transferred short day (8 h light per 24 h) acclimated Soay sheep to various longer photoperiods, simulating those occurring from spring to summer in their northerly habitat (57 degrees N). Locomotor activity and plasma melatonin rhythms remained synchronized to the light-dark cycle in all photoperiods. Surprisingly, transfer to 16-h light/day had a greater effect on prolactin secretion and oestrus activity than shorter (12 h) or longer (20 and 22 h) photoperiods. The 16-h photoperiod also had the largest effect on expression of circadian (per1) and neuroendocrine output (betaTSH) genes in the pars tuberalis and on kisspeptin gene expression in the arcuate nucleus of the hypothalamus, which modulates reproductive activity. This critical photoperiodic window of responsiveness to long days in mammals is predicted by a model wherein adenylate cyclase sensitization and clock gene phasing effects of melatonin combine to control neuroendocrine output. This adaptive mechanism may be related to the latitude of origin and the timing of the seasonal transitions.
Gabriela C Wagner; Jonathan D Johnston; Iain J Clarke; Gerald A Lincoln; David G Hazlerigg
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't     Date:  2007-09-27
Journal Detail:
Title:  Endocrinology     Volume:  149     ISSN:  0013-7227     ISO Abbreviation:  Endocrinology     Publication Date:  2008 Jan 
Date Detail:
Created Date:  2007-12-21     Completed Date:  2008-02-26     Revised Date:  2014-02-19    
Medline Journal Info:
Nlm Unique ID:  0375040     Medline TA:  Endocrinology     Country:  United States    
Other Details:
Languages:  eng     Pagination:  32-9     Citation Subset:  AIM; IM    
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MeSH Terms
Acclimatization / genetics*,  physiology*
Adenylate Cyclase / metabolism
CLOCK Proteins
Estrous Cycle / physiology
Eye Proteins / genetics,  metabolism
Gene Expression Regulation
Hypothalamus / metabolism,  physiology
Melatonin / blood*,  secretion
Models, Biological
Motor Activity / physiology
Period Circadian Proteins
Pineal Gland / metabolism,  physiology
Pituitary Gland, Anterior / metabolism,  physiology,  secretion
Thyrotropin, beta Subunit / genetics,  metabolism
Trans-Activators / genetics,  metabolism
Grant Support
G0600678//Medical Research Council
Reg. No./Substance:
0/Eye Proteins; 0/Period Circadian Proteins; 0/Thyrotropin, beta Subunit; 0/Trans-Activators; EC Proteins; EC Cyclase; JL5DK93RCL/Melatonin

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