Duration of melatonin regulates seasonal plasticity in subtropical Indian weaver bird, Ploceus philippinus

Surbhi, Yatinesh Kumari, Sangeeta Rani, Kazuyoshi Tsutsui, Vinod Kumar

    Research output: Contribution to journalArticle

    21 Citations (Scopus)

    Abstract

    Day length regulates seasonal plasticity connected with reproduction in birds. Rhythmic pineal melatonin secretion is a reliable indicator of the night length, hence day length. Removal of rhythmic melatonin secretion by exposure to constant bright light (LL<inf>bright</inf>) or by pinealectomy renders several species of songbirds including Indian weaver bird (Ploceus philippinus) arrhythmic. Present study investigated whether rhythmic melatonin is involved in the regulation of key reproductive neuropeptides (GnRH I and GnIH) and reproduction linked neural changes, viz. song control nuclei, in Indian weaver birds. Two experiments were performed using birds in an arrhythmic condition with low (under LL<inf>bright</inf>) or no (in the absence of pineal gland) endogenous melatonin. In experiment I, three groups of birds (n=5 each) entrained to 12L:12D were exposed to LL<inf>bright</inf> (25lux) for two weeks. Beginning on day 15 of LL<inf>bright</inf>, a control group received vehicle for 16h and two treatment groups were given melatonin in drinking water for 8h or 16h. In experiment II, one group of sham-operated and three groups of pinealectomized birds (n=5 each) entrained to 12L:12D were exposed to constant dim light (LL<inf>dim</inf>, 0.5lux). Beginning on day 15 of LL<inf>dim</inf>, three groups received similar treatment as in experiment I. Birds were perfused after thirty cycles of the melatonin treatment, and brain sections were immunohistochemically double-labeled for GnRH I and GnIH or Nissl stained. Activity was recorded throughout the experiments, while body mass and testes were measured at the beginning and end of the experiment. Birds were synchronized with melatonin cycles and measured the duration of melatonin as "night". Pinealectomized birds that received 16h of melatonin had significantly higher GnIH-ir cells than those received 8h melatonin; there was no difference in the GnRH I immunoreactivity between two treatment groups however. Intact birds that received long duration melatonin cycles exhibited small song control nuclei, specifically the high vocal center (HVC) and the robust nucleus of the arcopallium (RA), while birds that received short duration melatonin or no melatonin exhibited large HVC and RA. Thus, melatonin possibly regulates seasonal reproduction via GnIH secretion, and also controls seasonal neuroplasticity in the song control system in songbirds.

    Original languageEnglish
    Pages (from-to)46-54
    Number of pages9
    JournalGeneral and Comparative Endocrinology
    Volume220
    DOIs
    Publication statusPublished - 2015 Sep 1

    Fingerprint

    melatonin
    Melatonin
    Birds
    duration
    birds
    High Vocal Center
    Music
    Gonadotropin-Releasing Hormone
    animal communication
    Reproduction
    Songbirds
    songbirds
    secretion
    photoperiod
    pineal body
    Neuronal Plasticity
    Pineal Gland
    neuropeptides
    Neuropeptides
    Drinking Water

    Keywords

    • GnIH
    • GnRH I
    • HVC
    • Indian weaver bird
    • Melatonin
    • RA

    ASJC Scopus subject areas

    • Endocrinology

    Cite this

    Duration of melatonin regulates seasonal plasticity in subtropical Indian weaver bird, Ploceus philippinus. / Surbhi; Kumari, Yatinesh; Rani, Sangeeta; Tsutsui, Kazuyoshi; Kumar, Vinod.

    In: General and Comparative Endocrinology, Vol. 220, 01.09.2015, p. 46-54.

    Research output: Contribution to journalArticle

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