D2 Dopamine receptor subtype mediates the inhibitory effect of dopamine on TRH-induced prolactin release from the bullfrog pituitary

Masaki Nakano, Atsuko Minagawa, Itaru Hasunuma, Reiko Okada, Marie Christine Tonon, Hubert Vaudry, Kazutoshi Yamamoto, Sakae Kikuyama, Takeo Machida, Tetsuya Kobayashi

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    Abstract

    Dopamine receptors in mammals are known to consist of two D1-like receptors (D1 and D5) and three D2-like receptors (D2, D3 and D4). The aim of this study was to determine the dopamine receptor subtype that mediates the inhibitory action of dopamine on the release of prolactin (PRL) from the amphibian pituitary. Distal lobes of the bullfrog (Rana catesbeiana) were perifused and the amount of PRL released in the effluent medium was measured by means of a homologous enzyme-immunoassay. TRH stimulated the release of PRL from perifused pituitaries. Dopamine suppressed TRH-induced elevation of PRL release. Quinpirole (a D2 receptor agonist) also suppressed the stimulatory effect of TRH on the release of PRL, whereas SKF-38393 (a D1 receptor agonist) exhibited no such an effect. The inhibitory action of dopamine on TRH-induced PRL release from the pituitary was nullified by the addition of L-741,626 (a selective D2 receptor antagonist) to the medium, but not by the addition of SCH-23390 (a selective D1 receptor antagonist). These data indicate that the inhibitory effect of dopamine on TRH-evoked PRL release from the bullfrog pituitary gland is mediated through D2 dopamine receptors.

    Original languageEnglish
    Pages (from-to)287-292
    Number of pages6
    JournalGeneral and Comparative Endocrinology
    Volume168
    Issue number2
    DOIs
    Publication statusPublished - 2010 Sep

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    Keywords

    • Bullfrog
    • D2 receptor
    • Dopamine
    • Pituitary
    • Prolactin
    • Thyrotropin-releasing hormone

    ASJC Scopus subject areas

    • Endocrinology

    Cite this

    Nakano, M., Minagawa, A., Hasunuma, I., Okada, R., Tonon, M. C., Vaudry, H., Yamamoto, K., Kikuyama, S., Machida, T., & Kobayashi, T. (2010). D2 Dopamine receptor subtype mediates the inhibitory effect of dopamine on TRH-induced prolactin release from the bullfrog pituitary. General and Comparative Endocrinology, 168(2), 287-292. https://doi.org/10.1016/j.ygcen.2010.05.008