Document Detail

Daily rhythm of tryptophan hydroxylase-2 messenger ribonucleic acid within raphe neurons is induced by corticoid daily surge and modulated by enhanced locomotor activity.
MedLine Citation:
PMID:  17595225     Owner:  NLM     Status:  MEDLINE    
Tryptophan hydroxylase (TPH, the rate-limiting enzyme of serotonin synthesis) protein and mRNA levels display a circadian expression in the rat dorsal and median raphe. These patterns suggest a rhythmic synthesis of serotonin under the control of the master clock of suprachiasmatic nuclei. In the present study, we examined the involvement of endocrine and behavioral output signals of the master clock upon the Tph2 mRNA levels by quantitative in situ hybridization. In the absence of adrenals, a complete suppression of Tph2 mRNA rhythm was observed in dorsal and median raphe over 24 h. The restoration of corticosterone daily variations in adrenalectomized rats induced a Tph2 mRNA rhythmic pattern de novo, indicating that Tph2 mRNA rhythm is dependent upon daily fluctuations of glucocorticoids. Enhanced voluntary locomotor activity during 6 wk increased the level of Tph2 mRNA in both raphe nuclei of control rats without concomitant increase of corticosterone plasma levels. Moreover, this long-term enhanced locomotor activity was able to restore significant variation of Tph2 mRNA in adrenalectomized rats. In conclusion, both endocrine and behavioral cues can modulate Tph2 expression in dorsal and median raphe. The corticosterone surge acts as a rhythmic cue that induces the rhythmic expression of Tph2 in the raphe neurons. On the other hand, long-term exercise modulates the expression levels of this gene. Thus, the serotonin neurons are a target for both endocrine and behavioral circadian cues, and the serotoninergic input to the suprachiasmatic nuclei might feedback and influence the functioning of the clock itself.
Zeina S Malek; Dominique Sage; Paul Pévet; Sylvie Raison
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't     Date:  2007-06-26
Journal Detail:
Title:  Endocrinology     Volume:  148     ISSN:  0013-7227     ISO Abbreviation:  Endocrinology     Publication Date:  2007 Nov 
Date Detail:
Created Date:  2007-10-17     Completed Date:  2007-11-27     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  0375040     Medline TA:  Endocrinology     Country:  United States    
Other Details:
Languages:  eng     Pagination:  5165-72     Citation Subset:  AIM; IM    
Département de Neurobiologie des Rythmes, Institut des Neurosciences Cellulaires et Intégratives, 5 rue Blaise Pascal, F-67084, Strasbourg Cedex, France.
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MeSH Terms
Circadian Rhythm / physiology*
Corticosterone / blood,  pharmacology,  physiology*,  secretion
Gene Expression Regulation / drug effects
Motor Activity / physiology*
Neurons / metabolism
Pulsatile Flow / physiology
RNA, Messenger / metabolism
Raphe Nuclei / metabolism*
Rats, Wistar
Tryptophan Hydroxylase / genetics*,  metabolism
Reg. No./Substance:
0/RNA, Messenger; 50-22-6/Corticosterone; EC Hydroxylase; EC protein, rat
Comment In:
Endocrinology. 2007 Nov;148(11):5162-4   [PMID:  17940188 ]

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