Neuroendocrine regulation of thyroid-stimulating hormone secretion in amphibians

Reiko Okada*, Tetsuya Kobayashi, Kazutoshi Yamamoto, Takashi Nakakura, Shigeyasu Tanaka, Hubert Vaudry, Sakae Kikuyama

*Corresponding author for this work

    Research output: Chapter in Book/Report/Conference proceedingConference contribution

    29 Citations (Scopus)


    The hypothalamic peptides thyrotropin-releasing hormone (TRH), gonadotropin-releasing hormone (GnRH), and corticotropin-releasing factor (CRF), which have been postulated as acting as thyroid-stimulating hormone (TSH)-releasing hormone in amphibians, were tested for their activity by employing a recently developed radioimmunoassay for bullfrog (Rana catesbeiana) TSH. CRF markedly stimulated the release of TSH from both adult and larval bullfrog pituitary cells. Both TRH and GnRH moderately stimulated the release of TSH from adult pituitary cells but not from larval ones. The release of TSH was also enhanced by bullfrog hypothalamic extracts. The hypothalamic extract-evoked release of TSH was markedly reduced by a CRF receptor antagonist, suggesting that CRF and/or CRF-related peptides are the main TSH-releasing factors occurring in the bullfrog hypothalamus. Experiments using CRF receptor agonists and antagonists revealed that CRF acts through the type 2 receptor. With regard to other hypothalamic substances that influence the release of TSH, pituitary adenylate cyclase-activating polypeptide and vasoactive intestinal polypeptide were found to be potent stimulators and somatostatin an inhibitor of TSH release. Thus, it becomes clear that the main regulatory peptides controlling TSH secretion in amphibians are different from those in mammals. Triiodothyronine did not affect the basal release of TSH from the pituitary of either larval or adult bullfrogs but suppressed the CRF-induced release of TSH, suggesting that negative feedback by thyroid hormone is functioning both in larvae and adults.

    Original languageEnglish
    Title of host publicationAnnals of the New York Academy of Sciences
    Number of pages9
    Publication statusPublished - 2009 Apr

    Publication series

    NameAnnals of the New York Academy of Sciences
    ISSN (Print)00778923
    ISSN (Electronic)17496632


    • Amphibians
    • CRF
    • Negative feedback
    • PACAP
    • Somatostatin
    • Thyroid hormone
    • TSH release
    • VIP

    ASJC Scopus subject areas

    • Biochemistry, Genetics and Molecular Biology(all)


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