Blog
About

  • Record: found
  • Abstract: found
  • Article: not found

Characterizing a mammalian circannual pacemaker.

Science (New York, N.Y.)

Biological Clocks, physiology, Circadian Rhythm, Cues, Denervation, Lactotrophs, Male, Melatonin, blood, Models, Biological, Motor Activity, Photoperiod, Pineal Gland, innervation, Pituitary Gland, Anterior, secretion, Prolactin, Seasons, Sheep, Animals

Read this article at

ScienceOpenPublisherPubMed
Bookmark
      There is no author summary for this article yet. Authors can add summaries to their articles on ScienceOpen to make them more accessible to a non-specialist audience.

      Abstract

      Many species express endogenous cycles in physiology and behavior that allow anticipation of the seasons. The anatomical and cellular bases of these circannual rhythms have not been defined. Here, we provide strong evidence using an in vivo Soay sheep model that the circannual regulation of prolactin secretion, and its associated biology, derive from a pituitary-based timing mechanism. Circannual rhythm generation is seen as the product of the interaction between melatonin-regulated timer cells and adjacent prolactin-secreting cells, which together function as an intrapituitary "pacemaker-slave" timer system. These new insights open the way for a molecular analysis of long-term timing mechanisms.

      Related collections

      Most cited references 26

      • Record: found
      • Abstract: not found
      • Article: not found

      Circannual Rhythms

        Bookmark
        • Record: found
        • Abstract: found
        • Article: not found

        Biology of mammalian photoperiodism and the critical role of the pineal gland and melatonin.

        In mammals, photoperiodic information is transformed into a melatonin secretory rhythm in the pineal gland (high levels at night, low levels during the day). Melatonin exerts its effects in discrete hypothalamic areas, most likely through MT1 melatonin receptors. Whether melatonin is brought to the hypothalamus from the cerebrospinal fluid or the blood is still unclear. The final action of this indoleamine at the level of the central nervous system is a modulation of GnRH secretion but it does not act directly on GnRH neurones; rather, its action involves a complex neural circuit of interneurones that includes at least dopaminergic, serotoninergic and aminoacidergic neurones. In addition, this network appears to undergo morphological changes between seasons.
          Bookmark
          • Record: found
          • Abstract: found
          • Article: not found

          Circannual control of hibernation by HP complex in the brain.

          Seasonal hibernation in mammals is under a unique adaptation system that protects organisms from various harmful events, such as lowering of body temperature (Tb), during hibernation. However, the precise factors controlling hibernation remain unknown. We have previously demonstrated a decrease in hibernation-specific protein (HP) complex in the blood of chipmunks during hibernation. Here, HP is identified as a candidate hormone for hibernation. In chipmunks kept in constant cold and darkness, HP is regulated by an individual free-running circannual rhythm that correlates with hibernation. The level of HP complex in the brain increases coincident with the onset of hibernation. Such HP regulation proceeds independently of Tb changes in constant warmth, and Tb decreases only when brain HP is increased in the cold. Blocking brain HP activity using an antibody decreases the duration of hibernation. We suggest that HP, a target of endogenously generated circannual rhythm, carries hormonal signals essential for hibernation to the brain.
            Bookmark

            Author and article information

            Journal
            17185605
            10.1126/science.1132009

            Comments

            Comment on this article