Cell and Tissue Research

, Volume 324, Issue 1, pp 175–179 | Cite as

T3 implantation mimics photoperiodically reduced encasement of nerve terminals by glial processes in the median eminence of Japanese quail

  • Takashi Yamamura
  • Shinobu Yasuo
  • Kanjun Hirunagi
  • Shizufumi Ebihara
  • Takashi Yoshimura
Short Communication


Photoperiodically generated triiodothyronin (T3) in the mediobasal hypothalamus (MBH) has critical roles in the photoperiodic response of the gonads in Japanese quail. In a previous study, we demonstrated seasonal morphological changes in the neuro-glial interaction between gonadotrophin-releasing hormone (GnRH) nerve terminals and glial endfeet in the median eminence (ME). However, a direct relationship between photoperiodically generated T3 and seasonal neuro-glial plasticity in the ME remained unclear. In the present study, we examined the effect of T3 implantation into the MBH on the neuro-glial interaction in the ME. T3 implantation caused testicular growth and reduced encasement of nerve terminals in the external zone of the ME. In contrast, no morphological changes were observed in birds given an excessive dose of T3, which did not cause testicular growth. These results support the hypothesis that thyroid hormone regulates photoperiodic GnRH secretion via neuro-glial plasticity in the ME.


Thyroid hormone Glia Median eminence Photoperiodism Japanese quail 


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Copyright information

© Springer-Verlag 2006

Authors and Affiliations

  • Takashi Yamamura
    • 1
  • Shinobu Yasuo
    • 1
  • Kanjun Hirunagi
    • 3
  • Shizufumi Ebihara
    • 1
  • Takashi Yoshimura
    • 1
    • 2
  1. 1.Division of Biomodeling, Graduate School of Bioagricultural SciencesNagoya UniversityNagoyaJapan
  2. 2.Institute for Advanced ResearchNagoya UniversityNagoyaJapan
  3. 3. Nagoya University MuseumNagoyaJapan

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