Ziv Limor, Tovin Adi, Strasser Daniel, Gothilf Yoav
Department of Zoology, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel.
Exp Eye Res. 2007 Jan;84(1):92-9. doi: 10.1016/j.exer.2006.09.004. Epub 2006 Oct 24.
The pineal gland of the zebrafish (Danio rerio) is a clock-containing photoreceptive organ. Superfused pineal glands kept in darkness display rhythmic melatonin production that lasts for days, with high melatonin levels during the night and low levels during the day. Nocturnal light, however, evokes an acute suppression of melatonin synthesis in the photoreceptor cells. Towards characterizing zebrafish pineal photopigment that is involved in the acute melatonin suppression we have measured the spectral sensitivity of melatonin-suppression response in superfused pineal glands. The effect of 2 h light exposure of seven wavelengths (lambdaavg 408, 460, 512, 560, 608, 660 and 697+/-10-15 nm) at multiple irradiances (10(7)-10(14) photons/cm2/s) was determined, and an action spectrum was plotted. The resultant action spectrum provides evidence for the involvement of multiple photopigments in melatonin suppression. The most efficient melatonin-suppression response was achieved by exposure to light of around 512 nm; however, another peak of lower irradiance sensitivity was observed in the middle to long wavelengths. Opsins-specific RT-PCR analysis confirmed the expression of exo-rhodopsin and visual red-sensitive opsin in the pineal gland, while other zebrafish visual opsins as well as VA and VAL opsins were not detected. Dartnall monograms for exo-rhodopsin and visual red-sensitive opsin account for most but not all of the spectral sensitivity features. Therefore, additional pineal photopigments may contribute to the melatonin-suppression response in the pineal gland.
斑马鱼（Danio rerio）的松果体是一个含有生物钟的感光器官。置于黑暗中的离体灌注松果体可显示持续数天的节律性褪黑素分泌，夜间褪黑素水平高，白天水平低。然而，夜间光照会引起感光细胞中褪黑素合成的急性抑制。为了表征参与急性褪黑素抑制的斑马鱼松果体光色素，我们测量了离体灌注松果体中褪黑素抑制反应的光谱敏感性。测定了在多个辐照度（10⁷ - 10¹⁴ 光子/cm²/s）下，七种波长（平均波长408、460、512、560、608、660和697±10 - 15 nm）的2小时光照的影响，并绘制了作用光谱。所得的作用光谱为多种光色素参与褪黑素抑制提供了证据。通过暴露于约512 nm的光可实现最有效的褪黑素抑制反应；然而，在中长波长处观察到另一个较低辐照度敏感性的峰值。视蛋白特异性RT-PCR分析证实了松果体中外源视紫红质和视觉红色敏感视蛋白的表达，而未检测到其他斑马鱼视觉视蛋白以及VA和VAL视蛋白。外源视紫红质和视觉红色敏感视蛋白的达特纳尔图谱解释了大部分但不是所有的光谱敏感性特征。因此，额外的松果体光色素可能有助于松果体中的褪黑素抑制反应。
