Chloride Cotransporter Function in the Retina

描述（由申请人提供）：该研究项目是一项实验研究，旨在了解阳离子-氯化物协同转运蛋白在哺乳动物视网膜信息处理中的作用。在视网膜和中枢神经系统的其他地方，已经鉴定出两种类型的氯协同转运蛋白：Na-K-Cl 和 K-Cl 协同转运蛋白。这些氯离子协同转运蛋白调节细胞内氯离子浓度，使得 K-Cl 协同转运蛋白将氯离子从神经元中排出，而 Na-K-Cl 协同转运蛋白将氯离子转运到细胞内。因此，当氯离子平衡电位由于 K-Cl 协同转运蛋白的作用而低于静息膜电位时，神经递质 GABA 会使神经元超极化。相反，当氯平衡电位由于 Na-K-Cl 协同转运蛋白的作用而大于静息膜电位时，GABA 会使神经元去极化。因此，根据视网膜神经元表达的氯协同转运蛋白的类型，GABA 将使细胞超极化或去极化。因此，我们将结合电生理学、神经化学和解剖学技术来确定氯协同转运蛋白在视网膜中的作用。兔眼杯制剂将用于研究氯协同转运蛋白在方向选择性和从水平细胞到双极细胞的突触传递中的作用。具体来说，我们将确定星爆无长突细胞上 Na-K-Cl 和 K-Cl 协同转运蛋白的不对称分布是否介导兔 ON-OFF 定向选择性神经节细胞表现出的零方向抑制。我们还将确定水平细胞是否部分通过直接的、GABA 介导的突触连接（Na-K​​-Cl 共转运蛋白依赖性且符号保守）对 ON 中心双极细胞（和 ON 中心神经节细胞）的感受野周围做出贡献。最后，我们将确定氯离子协同转运蛋白功能的发育是否以及如何影响这些视网膜现象。增加对成人和发育中视网膜中氯离子协同转运蛋白功能的了解将有助于了解人类视网膜过程和功能障碍，并为视网膜疾病的药物治疗提供基础。

DESCRIPTION (provided by applicant): This research project is an experimental study that seeks to understand the role of cation-chloride co-transporters in information processing in the mammalian retina. In the retina and elsewhere in the central nervous system, two types of chloride co-transporters, the Na-K-Cl and K-Cl co-transporters, have been identified. These chloride co-transporters regulate the intracellular chloride concentration such that the K-Cl co-transporter extrudes chloride from neurons, whereas the Na-K-Cl co-transporter transports chloride into cells. Thus, the neurotransmitter GABA hyperpolarizes neurons when the chloride equilibrium potential is less than the resting membrane potential due to the action of the K-Cl co-transporter. In contrast, GABA depolarizes neurons when the chloride equilibrium potential is greater than the resting membrane potential due to the action of the Na-K-Cl co-transporter. Thus, depending on the type of chloride co-transporter expressed by a retinal neuron, GABA will either hyperpolarize or depolarize the cell.We will therefore determine the roles of chloride co-transporters in the retina by using a combination of electrophysiological, neurochemical and anatomical techniques. A rabbit eyecup preparation will be used to study the roles of chloride co-transporters in directional selectivity and in synaptic transmission from horizontal cells to bipolar cells. Specifically, we will determine whether an asymmetric distribution of the Na-K-Cl and K-Cl co-transporters on starburst amacrine cells mediates the null direction inhibition exhibited by rabbit ON-OFF directionally-selective ganglion cells. We will also determine whether horizontal cells contribute to the receptive field surround of ON-center bipolar cells (and ON-center ganglion cells) in part by a direct, GABA-mediated synaptic connection that is Na-K-Cl co-transporter-dependent and sign conserving. Finally, we will determine whether and how the development of chloride co-transporter function affects these retinal phenomena.Increased knowledge of chloride co-transporter function in the adult and developing retina will aid in the understanding of human retinal processes and dysfunction, as well as provide the basis for drug therapy for retinal disorders.