The aim of this study was to investigate the expression patterns of ocular melatonin in the annual reproductive cycle of the female grass puffer. Spawning season of the female grass puffer is from June to July in Jeju, South Korea. Time-resolved fluoroimmunoassay revealed that levels of ocular melatonin, which show an annual change, peaked in May (spawning season). Additionally, expression of reproductive-related genes also showed annual patterns: GnRH1 peaked in August, GnRH2 peaked in February, GnRH3, Kiss2, and LPXRFa peaked in November. These results suggest that ocular melatonin may be related to the annual reproductive cycle in the grass puffer. To better understand the photic regulation of AANAT1a mRNA in the retina, we observed the nocturnal pattern of ocular melatonin levels daily, which shows a nocturnal pattern in both short photoperiod (SD) and long photoperiod (LD) conditions. In the brain, AANAT2 mRNA also shows a nocturnal pattern in both SD and LD; however, the time of peak expression of AANAT2 mRNA was unchanged in both conditions. Following intraperitoneal injection of melatonin for 2 weeks, expression of GnRH2 and LPXRFa mRNA in the brain significantly increased, while that of Kiss2 mRNA was decreased, suggesting that melatonin has a reproduction-related effect. Furthermore, under SD and LD conditions for 14 weeks, the gonadosomatic index more increased and the maturity of the ovary progressed under LD compared with those under SD, suggesting that the SD photoperiodic signal inactivated ovarian development. These results indicate that the ocular melatonin may have a possible role in the reproductive endocrinology of the grass puffer.

中文翻译：

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雌性河豚（Takifugu alboplumbeus）眼褪黑激素水平的年度模式：可能参与季节性生殖反应。

这项研究的目的是调查雌性河豚一年生生殖周期中眼褪黑素的表达模式。在韩国济州，雌性河豚的产卵季节是六月至七月。时间分辨的荧光免疫测定显示，褪黑激素水平呈年度变化，在5月（产卵季节）达到峰值。此外，生殖相关基因的表达也显示出年度模式：GnRH1在8月达到峰值，GnRH2在2月达到峰值，GnRH3，Kiss2和LPXRFa在11月达到峰值。这些结果表明，眼褪黑激素可能与河豚的年度生殖周期有关。为了更好地了解视网膜中AANAT1a mRNA的光调节，我们每天观察眼部褪黑激素水平的夜间模式，在短光周期（SD）和长光周期（LD）情况下均显示夜间模式。在大脑中，AANAT2 mRNA在SD和LD中均表现出夜间行为。然而，在两种情况下，AANAT2 mRNA的峰值表达时间均未改变。腹膜内注射褪黑激素2周后，大脑中GnRH2和LPXRFa mRNA的表达显着增加，而Kiss2 mRNA的表达减少，这表明褪黑素具有生殖相关作用。此外，在SD和LD条件下持续14周，与SD相比，LD下的性腺体指数增加，并且LD的卵巢成熟发展，这表明SD的光周期信号使卵巢发育失活。