Functional characteristics of rod pathways in the retina

描述（由申请人提供）：本提案旨在了解哺乳动物视网膜中视杆回路的特性。我们的杆状视觉包含了10000个杆状光感受器，每个杆状光感受器可以吸收1000个或更多的光子。这种广泛的光敏度是由生物物理机制完成的，这一机制已经研究了半个多世纪，但仍有几个重要的根本性问题有待解决。本提案中描述的实验旨在解决两个问题：(1)杆光响应的哪些方面与下游加工相关？(2)将视杆光反应传递给神经节细胞的每条视网膜通路的光强度阈值和动态范围是什么？为了回答这些问题，我们将记录来自杆状光感受器、双极细胞和神经节细胞的光诱发反应，这些反应来自几种缺乏锥体光反应（锥体转导素-/-）的转基因小鼠系，其中：(1)杆状光传导途径的敲除改变了杆状光反应的形状，(2)视网膜回路的敲除将允许杆状视网膜通路（杆-双极、杆-锥和杆- off通路）进行分离研究。特定细胞中光传导蛋白（GCAP、视紫红质激酶、视紫红质和阻滞蛋白）或间隙连接蛋白连接蛋白36的缺失将改变光反应的传递，并使我们能够推断光反应和电路的特性如何影响杆视觉。在进行这些实验的同时，我们将评估每只小鼠的视杆视觉行为阈值。因此，视网膜中视杆信号的生理变化可以与受限的和可量化的视觉行为联系起来。这种相关性将为杆状光反应的处理如何影响感知提供见解，并将对理解杆状视觉缺陷（即静止夜盲症）的机制基础产生影响。

DESCRIPTION (provided by applicant): This proposal is aimed at understanding the properties of the rod circuitry in the mammalian retina. Our rod vision encompasses lights as dim as a single photon absorption in as many as 10,000 rod photoreceptors, up to 1000 or more photons per rod. This wide range of light sensitivity is accomplished by biophysical mechanisms that have been studied for more than a half century, but several outstanding issues of fundamental importance remain. The experiments described in this proposal are designed to address two issues: (1) Which aspects of the rod photoresponse are relevant for downstream processing?, and (2) What are the threshold and dynamic range of light intensities for each retinal pathway that relays the rod photoresponse to ganglion cells? To answer these questions we will record light-evoked responses from rod photoreceptors, bipolar cells and ganglion cells from several transgenic mouse lines lacking cone light responses (cone trasducin -/-) with: (1) knockouts in the rod phototransduction pathway that change the shape of the rod photoresponse, and (2) knockouts in the retinal circuitry that will allow the rod retinal pathways (Rod-Bipolar, Rod-Cone, and Rod-Off pathways) to be studied in isolation. The deletion of the phototransduction proteins (GCAP, Rhodopsin Kinase, Rhodopsin, and Arrestin), or the gap junction protein Connexin 36 in specific cells, will alter the transmission of light responses and allow us to infer how the properties of the photoresponse and circuitry influence rod vision. In parallel with these experiments, we will evaluate the behavioral threshold for rod vision in each mouse studied. Thus alterations in the physiology of rod signaling in the retina can be connected to a constrained and quantifiable visual behavior. Such correlations will provide insights into how the processing of the rod photoresponse influences perception, and will have consequences for understanding the mechanistic basis for deficits in rod vision (i.e. Stationary Night Blindness). Night vision in mammals is mediated by several pathways in the retina that relay information about few photon absorptions to the brain. This proposal is aimed at understanding how this remarkable sensitivity is achieved at the cellular level by establishing the properties of the rod photoreceptor response and the retinal circuitry that are important for visual processing. In order to devise therapies for conditions that influence our night vision, like Stationary Night Blindness, it is necessary to first understand the physiological mechanisms that relay information from our eyes to our brain at low light levels.