Short Communication

Cell and Tissue Research

, Volume 324, Issue 1, pp 175-179

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

  • Takashi YamamuraAffiliated withDivision of Biomodeling, Graduate School of Bioagricultural Sciences, Nagoya University
  • , Shinobu YasuoAffiliated withDivision of Biomodeling, Graduate School of Bioagricultural Sciences, Nagoya University
  • , Kanjun HirunagiAffiliated with Nagoya University Museum
  • , Shizufumi EbiharaAffiliated withDivision of Biomodeling, Graduate School of Bioagricultural Sciences, Nagoya University
  • , Takashi YoshimuraAffiliated withDivision of Biomodeling, Graduate School of Bioagricultural Sciences, Nagoya UniversityInstitute for Advanced Research, Nagoya University Email author 

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Abstract

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.

Keywords

Thyroid hormone Glia Median eminence Photoperiodism Japanese quail