ROD AND CONE SIGNALING PATHWAYS IN MAMMALIAN RETINA

项目总结/摘要 这项新研究项目的总体目标是了解杆细胞的详细突触机制， 以及哺乳动物视网膜中的视锥细胞信号通路。解剖学研究表明，视杆细胞和视锥细胞的通道， 哺乳动物视网膜遵循一套特定的电路规则：视杆细胞只在视杆细胞去极化的双极细胞上形成突触 DBCR不直接在神经节细胞（GC）上形成输出突触，而是通过AII无长突蛋白间接形成输出突触。 细胞（AIIAC）。AIIAC通过在视锥去极化和去极化上“捎带”将视杆介导的信号发送到ON和OFF GC， 超极化双极细胞（DBCC和HBCC），其分别在ON和OFF GC上突触。 在这项研究计划中，我们计划通过以下方式系统地研究这些特定的突触回路： 使用老鼠视网膜作为模型系统。除了使用全细胞电压钳（染料填充），解剖和 药理学技术，我们将利用四种途径特异性突变小鼠来阐明如何 哺乳动物的视杆细胞和视锥细胞信号被传递到BC、AC和GC，并确定是否有哺乳动物特异性的 电路规则是完全有效的，最近的证据和我们的初步结果表明，严格的杆/锥输入规则 可能并不适用于所有哺乳动物的视网膜神经元。我们将检验总体假设，即“小鼠DBCR亚群 接受来自视锥的直接突触输入，小鼠DBCC和HBCC的亚群接受直接突触输入 从视杆细胞，视杆细胞和视锥细胞介导的信号在发送到GC之前被AIIAC进一步混合， 对BC和GC的抑制性突触输入携带混合的视杆/视锥信号”。 本申请有3个具体目标，重点是研究视杆细胞和视锥细胞对光诱发阳离子的贡献， 氯电流（<$IC和<$ICl，分别代表谷氨酸能和GABA能/甘氨酸能突触输入）： (1)七种类型的双极电池（HBCMC/Rs、HBCMC、HBCSC、DBCC 2/MC、DBCC 1/MC/Rs、DBCR 2s、DBCR 1 s）;（2）AII （3）暗适应小鼠视网膜中的三种类型的α神经节细胞（ON、sOFF和tOFF）。 获得的结果将增加我们对平行通道，如杆/锥信号通路， 在眼睛和大脑中处理、分离和整合信息。由于许多视觉障碍与 在杆和锥信号通路的异常，这项研究项目将有助于确定细胞和突触的网站 是这些眼病的发病机制。

PROJECT SUMMARY/ABSTRACT The overall objective of this new research project is to understand detailed synaptic mechanisms underlying rod and cone signaling pathways in the mammalian retina. Anatomical studies have suggested that rod and cone channels in the mammalian retina follow a specific set of circuitry rules: rods make synapses only on rod depolarizing bipolar cells (DBCRs), and DBCRs do not make output synapses directly on ganglion cells (GCs), but indirectly through AII amacrine cells (AIIACs). AIIACs send rod-mediated signals to ON and OFF GCs by "piggybacking" on the cone depolarizing and hyperpolarizing bipolar cells (DBCCs and HBCCs), which synapse on ON and OFF GCs, respectively. In this research proposal, we plan to systematically investigate these mammalian-specific synaptic circuits by using the mouse retina as a model system. In addition to using whole-cell voltage clamp (with dye-filling), anatomical and pharmacological techniques, we will take advantage of four strains of pathway-specific mutant mice to elucidate how mammalian rod and cone signals are transmitted to BCs, ACs and GCs, and to determine whether the mammalian-specific circuitry rules are totally valid, as recent evidence and our preliminary results suggest that the strict rod/cone input rules may not hold for all mammalian retinal neurons. We will test the overall hypothesis that "subpopulations of mouse DBCRs receive direct synaptic inputs from cones and subpopulations of mouse DBCCs and HBCCs receive direct synaptic inputs from rods, the rod- and cone-mediated signals are further mixed by AIIACs before sending to GCs, and the AC-mediated inhibitory synaptic inputs to BCs and GCs carry mixed rod/cone signals". This application has 3 specific aims focused on studying rod and cone contributions to light-evoked cation and chloride currents (¿IC and ¿ICl, representing glutamatergic and GABAergic/glycinergic synaptic inputs, respectively) in: (1) seven types of bipolar cells (HBCMC/Rs, HBCMCs, HBCSCs, DBCC2/MCs, DBCC1/MC/Rs, DBCR2s, DBCR1s); (2) AII amacrine cells; and (3) three types of alpha ganglion cells (ON, sOFF and tOFF ¿GCs) in the dark-adapted mouse retina. Results obtained will increase our understanding of how parallel channels, such as the rod/cone signaling pathways, process, segregate and integrate information in the eye and in the brain. Since many visual disorders are associated with abnormalities in the rod and cone signaling pathways, this research project will help to identify cellular and synaptic sites responsible for the pathogenesis of these eye diseases.