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      Postnatal Development of TRH and TSH Rhythms in the Rat

      , , ,

      Hormone Research in Paediatrics

      S. Karger AG

      TRH, TSH, Rhythm, Ontogenesis, Rat

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          We previously observed that under a 12-hour light/12-hour dark schedule (lights off at 19.00 h), adult male Sprague-Dawley rats showed a circadian rhythm for serum thyroid-stimulating hormone (TSH) with a zenith near midday. In the present work, the ontogenesis of serum TSH rhythm was determined as well as pituitary TSH variations. In addition, hypothalamic and blood TRH were measured in these rats aged 15, 25, 40 and 70 days when sacrificed. As from the first age studied (15 days), a hypothalamic thyrotropin-releasing hormone (TRH) circadian rhythm was present. The mesor and the amplitude of this hypothalamic TRH rhythm increased while the rats were growing up, in contrast with the decrease observed for these parameters as far as blood TRH circadian rhythm is concerned. The time of the acrophase moved from 17.32 h in the 15-day-old rats to 13.57 h in the 70-day-old rats, being constantly in phase opposition with the blood TRH acrophase. The low amplitude pituitary TSH circadian rhythm detected in the young rat disappeared in the adult while, in contrast, the serum TSH rhythm became consistent to reach the well-characterized circadian midday peak in the 70-day-old rats.

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          Author and article information

          Horm Res Paediatr
          Hormone Research in Paediatrics
          S. Karger AG
          28 November 2008
          : 27
          : 4
          : 216-224
          Faculté de Médecine Alexis-Carrel, INSERM U-197, Lyon, France
          180823 Horm Res 1987;27:216–224
          © 1987 S. Karger AG, Basel

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          Pages: 9
          Original Paper


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