Potential roles for GNIH and GNRH-II in reproductive axis regulation of an opportunistically breeding songbird

Nicole Perfito, Richard Zann, Takayoshi Ubuka, George Bentley, Michaela Hau

    Research output: Contribution to journalArticle

    36 Citations (Scopus)

    Abstract

    The ability to breed at any time of year enables opportunistically breeding species to respond to good conditions whenever they occur. We investigate the neuroendocrine basis for this relatively unusual reproductive pattern in the avian world. One proposed mechanism for year-round breeding ability is tonic activation of gonadotropin-releasing hormone-I (GnRH-I) production that is flexibly modified by gonadotropin-inhibitory hormone (GnIH) production during unfavorable conditions. GnIH could inhibit GnRH secretion from the hypothalamus and/or inhibit GnRH action on the anterior pituitary gland. We studied neuroendocrine patterns in wild Australian zebra finches (Taeniopygia guttata) sampled during a breeding period in Southern Australia, a non-breeding period in central Australia, and in juvenile males in the latter location. We asked whether patterns in immunoreactivity of three neuropeptides important for reproductive axis regulation, GnRH-I, GnRH-II and GnIH, during periods of breeding and non-breeding reflect this flexibility. We found that the numbers and sizes of immunoreactive (-ir) GnRH-I cells did not vary between breeding stages and ages. Contrary to our predictions, irGnIH cell number and size, as well as the synthesis of GnIH mRNA were similar in breeding and non-breeding conditions. However, breeding males had more and larger irGnRH-II cells in the midbrain compared to non-breeding males. Hence, while changes in irGnIH cells are not associated with fluctuations in gonadotropin secretion or gonad volume, the regulation of irGnRH-II cells might represent a previously-unidentified mechanism by which reproductive flexibility can be achieved; namely via behavioral neurotransmitter actions of GnRH-II rather than through the typical sensory-CNS integration-GnRH-I route.

    Original languageEnglish
    Pages (from-to)20-26
    Number of pages7
    JournalGeneral and Comparative Endocrinology
    Volume173
    Issue number1
    DOIs
    Publication statusPublished - 2011 Aug 1

    Fingerprint

    Songbirds
    songbirds
    Breeding
    Gonadotropin-Releasing Hormone
    gonadotropins
    Gonadotropins
    gonadotropin-releasing hormone
    breeding
    hormones
    Hormones
    Taeniopygia guttata
    cells
    secretion
    Finches
    anterior pituitary
    Anterior Pituitary Gland
    Equidae
    neuropeptides
    Gonads
    hypothalamus

    Keywords

    • GnIH
    • GnRH
    • HPG axis
    • Neuroendocrine
    • Opportunistic breeding
    • Timing of reproduction
    • Zebra finch

    ASJC Scopus subject areas

    • Endocrinology

    Cite this

    Potential roles for GNIH and GNRH-II in reproductive axis regulation of an opportunistically breeding songbird. / Perfito, Nicole; Zann, Richard; Ubuka, Takayoshi; Bentley, George; Hau, Michaela.

    In: General and Comparative Endocrinology, Vol. 173, No. 1, 01.08.2011, p. 20-26.

    Research output: Contribution to journalArticle

    Perfito, Nicole ; Zann, Richard ; Ubuka, Takayoshi ; Bentley, George ; Hau, Michaela. / Potential roles for GNIH and GNRH-II in reproductive axis regulation of an opportunistically breeding songbird. In: General and Comparative Endocrinology. 2011 ; Vol. 173, No. 1. pp. 20-26.
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