T3 implantation mimics photoperiodically reduced encasement of nerve terminals by glial processes in the median eminence of Japanese quail |
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Authors: | Takashi Yamamura Shinobu Yasuo Kanjun Hirunagi Shizufumi Ebihara Takashi Yoshimura |
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Affiliation: | (1) Division of Biomodeling, Graduate School of Bioagricultural Sciences, Nagoya University, Furo-cho, Chikusa-ku, 464-8601 Nagoya, Japan;(2) Institute for Advanced Research, Nagoya University, Furo-cho, Chikusa-ku, 464-8601 Nagoya, Japan;(3) Nagoya University Museum, Furo-cho, Chikusa-ku, 464-8601 Nagoya, Japan |
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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. T. Yoshimura was supported by the Program for Promotion of Basic Research Activities for Innovative Biosciences (PROBRAIN) and a Grant-in-Aid for Encouragement of Young Scientists from the Ministry of Education, Science, Sports, and Culture, Japan. |
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Keywords: | Thyroid hormone Glia Median eminence Photoperiodism Japanese quail |
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