Zisapel N, Nir I, Laudon M
Department of Biochemistry, George S. Wise Faculty of Life Sciences, Tel-Aviv University, Israel.
FEBS Lett. 1988 May 9;232(1):172-6. doi: 10.1016/0014-5793(88)80411-3.
The binding of 125I-melatonin to synaptosomes prepared from whole brains of male rats of the CD strain and from the brain, hypothalamus and striatum of male rats of the Sabra-Wistar strain was assessed throughout a 24 h period. The animals were maintained under a daily schedule of 14 h light (05:00-19:00 h) and 10 h darkness. In whole brain preparations the density of binding sites at 18:00 h was higher by about 70% than at 02:00 h with no variations in apparent affinity of the binding sites throughout the daily period. Specific binding of 125I-melatonin was found in both hypothalamus and striatum of the male rat with a distinct diurnal variation in binding site density in the hypothalamus only. The density of 125I-melatonin-binding sites in the hypothalamus was maximal between 10:00 and 18:00 h and dropped sharply after the lights went off. The apparent 125I-melatonin-binding affinities in these regions were constant and very similar to those in whole brain preparations. The daily variations in densities of 125I-melatonin-binding sites in discrete brain areas may represent a diurnal rhythmicity in the responsiveness of the neuroendocrine axis to melatonin.
在24小时期间，评估了125I-褪黑素与CD品系雄性大鼠全脑以及Sabra-Wistar品系雄性大鼠脑、下丘脑和纹状体制备的突触体的结合情况。动物维持在每天14小时光照（05:00 - 19:00 h）和10小时黑暗的时间表下。在全脑制备物中，18:00 h时结合位点的密度比02:00 h时高约70%，且在整个白天期间结合位点的表观亲和力没有变化。在雄性大鼠的下丘脑和纹状体中均发现了125I-褪黑素的特异性结合，仅下丘脑的结合位点密度有明显的昼夜变化。下丘脑125I-褪黑素结合位点的密度在10:00至18:00 h之间最大，熄灯后急剧下降。这些区域中125I-褪黑素的表观结合亲和力是恒定的，并且与全脑制备物中的非常相似。离散脑区中125I-褪黑素结合位点密度的每日变化可能代表神经内分泌轴对褪黑素反应性的昼夜节律。
