Photoperiod and reproductive condition are associated with changes in RFamide-Related Peptide (RFRP) expression in Syrian hamsters (Mesocricetus auratus)

Alex O. Mason, Sean Duffy, Sheng Zhao, Takayoshi Ubuka, George E. Bentley, Kazuyoshi Tsutsui, Rae Silver, Lance J. Kriegsfeld

    Research output: Contribution to journalArticlepeer-review

    58 Citations (Scopus)

    Abstract

    To conserve scarce energetic resources during winter, seasonal breeders inhibit reproduction and other nonessential behavioral and physiological processes. Reproductive cessation is initiated in response to declining day lengths, a stimulus represented centrally as a long-duration melatonin signal. The melatonin signal is not decoded by the reproductive axis directly, but by an unidentified neurochemical system upstream of gonadotropin-releasing hormone (GnRH). The dorsomedial nucleus of the hypothalamus (DMH) has been implicated in seasonal changes in reproductive function in Syrian hamsters (Mesocricetus auratus), although the specific-cell phenotype decoding photoperiodic information remains unknown. RFamide-related peptide (RFRP; the mammalian homolog of the gonadotropin-inhibitory hormone (GnIH) gene identified in birds) has emerged as a potent inhibitory regulator of the reproductive axis and, significantly, its expression is localized to cell bodies of the DMH in rodents. In the present study, the authors explored the relationship between RFRP expression, photoperiod exposure, and reproductive condition/hormonal status. In male hamsters that respond to short days with reproductive inhibition, RFRP-ir and mRNA expression are markedly reduced relative to long-day animals. Replacement of testosterone in short-day animals did not affect this response, suggesting that alterations in RFRP expression are not a result of changing sex steroid concentrations. A subset of the hamster population that ignores day length cues and remains reproductively competent in short days (nonresponders) exhibits RFRP-ir expression comparable to long-day hamsters. Analysis of cell body and fiber density suggests a potential interplay between peptide production and release rate in differentially regulating the reproductive axis during early and late stages of reproductive regression. Together, the present findings indicate that photoperiod-induced suppression of reproduction is associated with changes in RFRP and mRNA expression, providing opportunity for further exploration on the role that RFRP plays in this process.

    Original languageEnglish
    Pages (from-to)176-185
    Number of pages10
    JournalJournal of Biological Rhythms
    Volume25
    Issue number3
    DOIs
    Publication statusPublished - 2010 Jun

    Keywords

    • DMH
    • Gonad
    • Melatonin
    • Photoperiod
    • Reproduction
    • Seasonal

    ASJC Scopus subject areas

    • Physiology
    • Physiology (medical)

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