Scher Judite, Wankiewicz Ellen, Brown Gregory M, Fujieda Hiroki
Department of Physiology, Faculty of Medicine, University of Toronto, Medical Sciences Building, 1 Kings College Circle, Rm 3321, Ont., M5S 1A8, Toronto, Canada.
Exp Eye Res. 2003 Sep;77(3):375-82. doi: 10.1016/s0014-4835(03)00123-4.
AII amacrine cells are critical interneurons in the rod pathway of mammalian retina, active primarily in dim lighting conditions. Melatonin, a neuromodulator produced at night in the retina, is believed to induce retinal adaptation to dim lighting conditions in most vertebrate species examined to date, including humans. We hypothesized that melatonin may influence retinal light adaptation by acting on AII cells directly and thus investigated whether melatonin receptors were expressed in AII neurons. Postmortem nonpathological eyes from four human donors as well as two eyes from two Macaque Fasicularis monkeys were analyzed. Double immunocytochemistry was performed using an anti-MT(1) antibody and an antibody to calretinin, an AII marker. Analysis utilized confocal microscopy. A polyclonal anti-calretinin antibody labelled amacrine cells exhibiting the distinct AII morphology, in both human and macaque retina. MT(1) immunoreactivity in macaque retina was similar to human staining, in that horizontal, amacrine and ganglion cell bodies were stained, as were inner segments of photoreceptors. In human retina 86% of calretinin positive cells expressed the MT(1) receptor peripherally, whereas centrally, 78% colocalization was observed. In the macaque retina, 100% of AII amacrine cells expressed MT(1) immunoreactivity both centrally and peripherally. That virtually all AII neurons express the MT(1) receptor in both human and macaque retina, may provide the first evidence demonstrating a role for melatonin in AII regulation, furthering the hypothesis of melatonin function in retinal light adaptation.
所有无长突细胞都是哺乳动物视网膜视杆通路中的关键中间神经元，主要在暗光条件下活跃。褪黑素是一种夜间在视网膜中产生的神经调质，据信在包括人类在内的迄今所研究的大多数脊椎动物物种中，它能诱导视网膜适应暗光条件。我们假设褪黑素可能通过直接作用于无长突细胞来影响视网膜光适应，因此研究了无长突细胞神经元中是否表达褪黑素受体。分析了来自四名人类供体的死后非病理性眼睛以及来自两只猕猴的两只眼睛。使用抗MT(1)抗体和一种针对无长突细胞标志物钙视网膜蛋白的抗体进行双重免疫细胞化学。分析采用共聚焦显微镜。一种多克隆抗钙视网膜蛋白抗体在人类和猕猴视网膜中标记出呈现独特无长突细胞形态的无长突细胞。猕猴视网膜中的MT(1)免疫反应性与人类染色相似，即水平细胞、无长突细胞和神经节细胞体被染色，光感受器的内段也被染色。在人类视网膜中，86%的钙视网膜蛋白阳性细胞在外周表达MT(1)受体，而在中央，观察到78%的共定位。在猕猴视网膜中，100%的无长突无长突细胞在中央和外周均表达MT(1)免疫反应性。几乎所有无长突细胞神经元在人类和猕猴视网膜中都表达MT(1)受体，这可能首次证明了褪黑素在无长突细胞调节中的作用，进一步支持了褪黑素在视网膜光适应中发挥作用的假说。
