Document Detail

The photoperiodic response in Syrian hamster depends upon a melatonin-driven circadian rhythm of sensitivity to melatonin.
MedLine Citation:
PMID:  8748127     Owner:  NLM     Status:  MEDLINE    
The pineal gland, via the daily pattern of melatonin (MEL) secretion, is directly involved in the conduction of photoperiodic information. The duration of MEL secretion is proportional to the duration of the dark period and, whatever the photoperiod is, MEL synthesis occurs 3 or 4 h after the dark onset in Syrian hamsters. In order to determine the relative importance of the duration or the coincidence hypothesis, a daily infusion protocol was used in sexually active pinealectomized hamsters. Long duration of MEL infusion (10 h) completely inhibit testes whereas short duration infusion (5 h) had no effect. When the animals were infused twice within 2 h 30 min separated by 3 h, they presented a complete gonadal atrophy, similar to the one observed with the 10 h infusion. Measurement of plasma MEL during the infusion and separation periods revealed that MEL reached physiological nighttime values during the infusion period and fell to daytime values 1 h after the end of an infusion period. Thus, the results could not be due to a time additive action of the two MEL pulses. An intermediate response was observed when the 2 signals were applied across the light/dark transition. Gonadal regression did not occur when the 2 periods of infusion were separated by 5 h 30 min. The efficiency of this type of infusion was not dependent on the ambiant photoperiod since similar results were obtained in long and short photoperiods. The infusion was also as effective during the day as well as during the night. These results suggest that there is a rhythm of sensitivity to MEL, based on the coincidence hypotheses, that are important for transmission of photoperiodic information. This rhythm of sensitivity to MEL seems to be entrained by MEL itself, since the efficiency of the two pulses of MEL is not dependent of time of application and/or of photoperiod.
B Pitrosky; R Kirsch; B Vivien-Roels; I Georg-Bentz; B Canguilhem; P Pevet
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Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  Journal of neuroendocrinology     Volume:  7     ISSN:  0953-8194     ISO Abbreviation:  J. Neuroendocrinol.     Publication Date:  1995 Nov 
Date Detail:
Created Date:  1996-10-11     Completed Date:  1996-10-11     Revised Date:  2005-11-17    
Medline Journal Info:
Nlm Unique ID:  8913461     Medline TA:  J Neuroendocrinol     Country:  ENGLAND    
Other Details:
Languages:  eng     Pagination:  889-95     Citation Subset:  IM    
CNRS-URA 1332, Neurobiologie des fonctions rythmiques et saisonnières, Université Louis Pasteur, Strasbourg, France.
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MeSH Terms
Circadian Rhythm / drug effects*,  physiology
Melatonin / pharmacology*
Organ Size
Pineal Gland / metabolism
Sensitivity and Specificity
Testis / drug effects
Time Factors
Reg. No./Substance:
Comment In:
J Neuroendocrinol. 1996 Jun;8(6):481-2   [PMID:  8809679 ]
J Neuroendocrinol. 1996 Jun;8(6):482-6   [PMID:  8809680 ]

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