Absence of circadian clock regulation of horizontal cell gap junctional coupling reveals two dopamine systems in the goldfish retina
Absence of circadian clock regulation of horizontal cell gap junctional coupling reveals two dopamine systems in the goldfish retina
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DOI：
10.1002/cne.10927
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发表时间：
2003-12-08
影响因子：
2.5
通讯作者：
Mangel, SC
中科院分区：
文献类型：
--
作者：
Ribelayga, C;Mangel, SC
在鱼类和其他脊椎动物视网膜中，虽然多巴胺的释放受光和内源性昼夜节律（24小时）钟的调节，但光比生物钟更能增加多巴胺的释放。生物钟在主观的一天中增加多巴胺的释放，从而激活D-2样受体。然而，目前尚不清楚视网膜时钟是否也激活D-1受体，D-1受体在完整组织中对多巴胺的敏感性要低得多。由于激活的D-1受体的鱼锥水平（H1）细胞解偶联细胞之间的差距连接，我们研究了时钟是否调节生物胞素示踪剂耦合的程度在金鱼视网膜。H1细胞之间的示踪剂耦合是广泛的暗适应条件下（低暗适应范围）和类似的主观白天，主观夜晚，白天和夜晚。在每个暗适应条件下平均偶联约180个细胞。然而，强光刺激或应用D-1激动剂SKF 38393（10 μ M）显著降低H1细胞偶联。D-2激动剂quinpirole（1 μ M）或D-1拮抗剂SCH 23390（10 μ M）和/或D-2拮抗剂spiperone（10 μ M）的应用对暗适应视网膜中的H1细胞偶联没有影响。这些观察结果表明，H1细胞间隙连接偶联，从而D-1受体活性不受内源性多巴胺在黑暗适应条件下。结果表明，金鱼视网膜中存在两种不同的多巴胺系统。一个系统由内源性时钟控制，在白天激活低阈值D-2样受体，而第二个系统由光控制，涉及较高阈值D-1受体的激活。(C)2003 Wiley-Liss，Inc.
In fish and other vertebrate retinas, although dopamine release is regulated by both light and an endogenous circadian (24-hour) clock, light increases dopamine release to a greater extent than the clock. The clock increases dopamine release during the subjective day so that D-2-like receptors are activated. It is not known, however, whether the retinal clock also activates D-1 receptors, which display a much lower sensitivity to dopamine in intact tissue. Because activation of the D-1 receptors on fish cone horizontal (H1) cells uncouples the gap junctions between the cells, we studied whether the clock regulates the extent of biocytin tracer coupling in the goldfish retina. Tracer coupling between H1 cells was extensive under dark-adapted conditions (low scotopic range) and similar in the subjective day, subjective night, day, and night. An average of approximately 180 cells were coupled in each dark-adapted condition. However, bright light stimulation or application of the D-1 agonist SKF38393 (10 muM) dramatically reduced H1 cell coupling. The D-2 agonist quinpirole (1 muM) or application of the D-1 antagonist SCH23390 (10 muM) and/or the D-2 antagonist spiperone (10 muM) had no effect on H1 cell coupling in dark-adapted retinas. These observations demonstrate that H1 cell gap junctional coupling and thus D-1 receptor activity are not affected by endogenous dopamine under dark-adapted conditions. The results suggest that two different dopamine systems are present in the goldfish retina. One system is controlled by an endogenous clock that activates low threshold D-2-like receptors in the day, whereas the second system is controlled by light and involves activation of higher threshold D-1 receptors. (C) 2003 Wiley-Liss, Inc.