Regulation of Capillary Blood Flow in the Retina in Health and in Diabetic Retinopathy

 描述（由申请人提供）：血流的适当调节对视网膜的健康和功能至关重要。闪烁刺激引起视网膜血流量增加，这种反应称为功能性充血。这种反应为活跃的神经元带来额外的氧气和葡萄糖。我们最近已经证明，在视网膜中的三个毛细血管层内，血流受到不同的调节。闪烁的光引起毛细血管直径和血流量在中间毛细血管层中比在深层和浅层中大得多的增加。该项目的目标是确定负责这种血流差异控制的机制，并确定这种控制是否在糖尿病视网膜病变中改变，其中已知功能性充血被破坏。该项目的目标是：目标1。测试假设，即中间层毛细血管的选择性扩张是由附近神经元的活动驱动的。中间层毛细血管的大闪烁诱发反应可能是因为这些毛细血管附近的突触活动大于其他毛细血管层附近的活动，导致血管舒张剂的释放更多。这一假设将通过使用Müller神经胶质细胞内的局部Ca2+信号作为附近突触活动的指标来检验。钙信号将在不同的视网膜层成像使用转基因小鼠表达的遗传 在Müller细胞中编码Ca2+指示剂GCaMP3。目标2.验证闪烁诱发的毛细血管扩张是由花生四烯酸代谢产物介导的假设。将在大鼠体内三个毛细血管层中监测闪烁诱发的毛细血管扩张，因为通过玻璃体内注射合成抑制剂阻断候选血管扩张剂的信号传导。还将候选血管扩张剂注射到玻璃体液中，并监测三个毛细血管层中毛细血管直径的变化。目标3。检验糖尿病视网膜病变中中层毛细血管扩张受损的假设。毛细管直径 在通过链脲佐菌素注射诱导糖尿病后0.5、1、3和6个月测量三个毛细血管层。将研究氨基胍对毛细血管扩张的作用，氨基胍可逆转糖尿病视网膜中小动脉扩张的丧失。

 DESCRIPTION (provided by applicant): Proper regulation of blood flow is essential for the health and function of the retina. Flicker stimulation evokes increases in blood flow in the retina a response termed functional hyperemia. This response brings additional oxygen and glucose to active neurons. We have recently demonstrated that blood flow is differentially regulated within the three capillary layers in the retina. Flickering light evokes far greater increases in capillar diameter and blood flow in the intermediate capillary layer than in the deep and superficial layers. The goal of this project is to determine the mechanisms responsible for this differential control of blood flow and to establish whether this control is altered in diabetic retinopathy, where functional hyperemia is known to be disrupted. The aims of the project are: Aim 1. Test the hypothesis that selective dilation of intermediate layer capillaries is driven by the activity f nearby neurons. The large flicker-evoked responses of intermediate layer capillaries may arise because synaptic activity near these capillaries is greater than activity near the other capillary layers, leading to greater release of vasodilating agents. This hypothesis will be tested by using local Ca2+ signals within Müller glial cells as an indicator of nearby synaptic activity. Calcium signals will be imaged in different retinal layers using transgenic mice expressing the genetically encoded Ca2+ indicator GCaMP3 in Müller cells. Aim 2. Test the hypothesis that flicker-evoked dilations of capillaries is mediated by production of arachidonic acid metabolites. Flicker-evoked capillary dilations will be monitored in the rat in vivo in the three capillary layers as the signaing of candidate vasodilators is blocked by intravitreal injection of synthesis inhibitors. Candidate vasodilators will also be injected into the vitreous humor and the resulting changes in capillary diameter in the three capillary layers will be monitored. Aim 3. Test the hypothesis that dilation of intermediate layer capillaries is compromised in diabetic retinopathy. Capillary diameter in the three capillary layers will be measured at 0.5, 1, 3 and 6 months after diabetes induction by streptozotocin injection. The effect of aminoguanidine, which reverses the loss of arteriole dilation in the diabetic retina, on capillary dilation will be investigated.