title: Glucocorticoid-mediated nycthemeral and photoperiodic regulation of tph2 expression.
abstract: In the Syrian hamster dorsal and median raphé nuclei, the tryptophan hydroxylase 2 gene (tph2), which codes the rate-limiting enzyme of serotonin synthesis, displays daily variations in its expression in animals entrained to a long but not to a short photoperiod. The present study aimed to assess the role of glucocorticoids in the nycthemeral and photoperiodic regulation of daily tph2 expression. In hamsters held in long photoperiod from birth, after adrenalectomy and glucocorticoid implants the suppression of glucocorticoid rhythms induced an abolition of the daily variations in tph2-mRNA concentrations, a decrease in the amplitude of body temperature rhythms and an increase in testosterone levels. All these effects were reversed after experimental restoration of a clear daily rhythm in the plasma glucocorticoid concentrations. We conclude that the photoperiod-dependent rhythm of glucocorticoids is the main regulator of tph2 daily expression.
authors.affiliation: Département de Neu\robiologie des Rythmes, Institut des Neurosciences Cellulaires et Intégratives, CNRS UPR-3212, 5 rue Blaise Pascal, 67084 Strasbourg, France.
authors.forename: Laurent
authors.initials: L
authors.lastname: Nexon
authors.forename: Dominique
authors.initials: D
authors.lastname: Sage
authors.forename: Paul
authors.initials: P
authors.lastname: Pévet
authors.forename: Sylvie
authors.initials: S
authors.lastname: Raison
mesh_terms: D000315:Adrenalectomy; D000818:Animals; D001683:Biological Clocks / Q000187:drug effects / Q000502:physiology; D001831:Body Temperature; D002940:Circadian Rhythm / Q000187:drug effects*; D006224:Cricetinae; D015870:Gene Expression / Q000187:drug effects*; D005938:Glucocorticoids / Q000494:pharmacology*; D017403:In Situ Hybridization; D008297:Male; D008647:Mesocricetus; D009919:Orchiectomy; D017440:Photoperiod; D020033:Protein Isoforms / Q000235:genetics* / Q000378:metabolism; D011903:Raphe Nuclei / Q000187:drug effects / Q000201:enzymology / Q000502:physiology; D013739:Testosterone / Q000097:blood; D014365:Tryptophan Hydroxylase / Q000235:genetics* / Q000378:metabolism
chemical_list: D005938:Glucocorticoids; D020033:Protein Isoforms; D013739:Testosterone; D014365:Tryptophan Hydroxylase