Dissecting a microcircuit that regulates the earliest light responses in the retina

- 项目概要- 在视网膜中，视网膜神经节细胞（RGC）的子集是固有光敏的（ipRGC），因为 它们表达一种叫做黑视素的光敏色素。因此，IpRGC可以编码环境光强度 而没有来自视杆和视锥光感受器的输入。在视网膜发育期间，ipRGC是视网膜发育的唯一来源。 在视杆和视锥光感受器成熟之前视网膜中的光诱发活动。IpRGC是必要的， 新生动物的多种行为，包括瞳孔对光反射、光厌恶和光诱导 睡眠/觉醒周期。越来越多的证据表明ipRGC通过间隙连接电偶联。 此外，我们实验室最近的一项研究表明，视网膜中的多巴胺信号调节了视网膜的强度。 电路中的电耦合。 在这个建议中，我们探讨了多巴胺能调节电耦合之间的假设， ipRGC影响ipRGC的光敏感性和它们引起的行为。有多个 视网膜中的ipRGC类型，其介导不同的行为。作为理解 由于ipRGC之间的电耦合的功能，我们在目标1中提出使用电路映射技术来 识别哪些ipRGC类型参与电耦合。使用钙成像，我们将确定是否 特定类型的ipRGC之间的电耦合增强了它们对光的敏感性。以确定如何 多巴胺信号调节ipRGC之间的电偶联，我们将使用交叉转基因 这是一种特异性敲除ipRGC中多巴胺受体的策略。然后我们会用电生理学 实验以确定多巴胺信号传导是否降低ipRGC之间的电耦合强度。 在目标2中，我们建议使用行为测试来确定ipRGC之间的电耦合强度是否 调节它们所介导的行为的光敏感性。

-Project Summary- In the retina, a subset of retinal ganglion cells (RGCs) are intrinsically photosensitive (ipRGCs) because they express a light-sensitive pigment called melanopsin. IpRGCs can therefore encode ambient light intensity without input from rod and cone photoreceptors. During retinal development, ipRGCs are the sole source of light-evoked activity in the retina before rod and cone photoreceptors mature. IpRGCs are necessary for multiple behaviors in neonatal animals, including the pupillary light reflex, light aversion, and light entrainment of sleep/wake cycles. Mounting evidence indicates that ipRGCs are electrically coupled through gap junctions. Additionally, a recent study in our lab suggests that dopamine signaling in the retina regulates the strength of electrical coupling in this circuit. In this proposal, we explore the hypothesis that dopaminergic modulation of electrical coupling between ipRGCs influences the light sensitivity of ipRGCs and of the behaviors that they evoke. There are multiple types of ipRGCs in the retina, which mediate distinct behaviors. As a first step toward understanding the function of electrical coupling between ipRGCs, we propose in Aim 1 to use a circuit mapping technique to identify which ipRGC types participate in electrical coupling. Using calcium imaging, we will then determine if electrical coupling between specific types of ipRGCs enhances their sensitivity to light. To determine how dopamine signaling modulates electrical coupling between ipRGCs, we will use an intersectional transgenic strategy to knock out dopamine receptors specifically in ipRGCs. We will then use electrophysiology experiments to determine if dopamine signaling decreases the strength of electrical coupling between ipRGCs. In Aim 2, we propose to use behavioral tests to determine if the strength of electrical coupling between ipRGCs modulates the light sensitivity of the behaviors they mediate.