Chloride Cotransporter Function in the Retina

描述（由申请人提供）：本研究项目是一项旨在了解阳离子-氯共转运体在视网膜信息处理中的作用的实验研究。在视网膜和中枢神经系统的其他地方，已经确定了两种类型的氯共转运体，Na-K-2Cl （NKCC）和K-Cl （KCC）共转运体。这些氯离子共转运体调节细胞内氯离子浓度，使KCC从神经元中挤出氯离子，而NKCC将氯离子转运到细胞中。因此，由于KCC的作用，当氯离子平衡电位比静息膜电位更负时，打开氯离子通道的神经递质GABA会使神经元超极化。相反，由于NKCC的作用，当氯离子平衡电位大于静息膜电位时，GABA会使神经元去极化。因此，视视网膜神经元表达的氯共转运体的类型而定，GABA会使细胞超极化或去极化。因此，我们将通过结合电生理、神经化学、细胞/分子和解剖学技术来确定氯共转运体在视网膜中的作用。利用兔眼杯神经视网膜制备物，研究氯离子共转运体在外视网膜的定向选择性和突触传递中的作用。具体来说，我们将确定氯离子共转运体活性是否介导双极细胞和神经节细胞在光适应条件下的感受野。我们还将确定氯共转运体在星爆无突细胞的定向选择性光响应中的作用，星爆无突细胞是突触前的中间神经元，具有ON-OFF定向选择性神经节细胞。公共卫生相关性：增加对成人视网膜中氯共转运蛋白活性的了解将有助于了解人类视网膜功能和功能障碍，并为涉及氯共转运蛋白的视网膜疾病（如视网膜缺血）的药物治疗提供基础。此外，增加对氯化物共转运体的了解可能有助于理解和治疗癫痫和其他涉及氯化物稳态和GABA的疾病。

DESCRIPTION (provided by applicant): This research project is an experimental study that seeks to understand the role of cation-chloride cotransporters in information processing in the retina. In the retina and elsewhere in the central nervous system, two types of chloride cotransporter, the Na-K-2Cl (NKCC) and K-Cl (KCC) cotransporters, have been identified. These chloride cotransporters regulate the intracellular chloride concentration such that KCC extrudes chloride from neurons, whereas NKCC transports chloride into cells. Thus, the neurotransmitter GABA, which opens chloride channels, hyperpolarizes neurons when the chloride equilibrium potential is more negative than the resting membrane potential due to the action of KCC. In contrast, GABA depolarizes neurons when the chloride equilibrium potential is more positive than the resting membrane potential due to the action of NKCC. Thus, depending on the type of chloride cotransporter expressed by a retinal neuron, GABA will either hyperpolarize or depolarize the cell. We will therefore determine the roles of chloride cotransporters in the retina by using a combination of electrophysiological, neurochemical, cell/molecular and anatomical techniques. The rabbit eyecup neural retina preparation will be used to study the roles of chloride cotransporters in directional selectivity and in synaptic transmission in the outer retina. Specifically, we will determine whether chloride cotransporter activity mediates the receptive field surround of bipolar cells and ganglion cells under light- adapted conditions. We will also determine the roles of the chloride cotransporters in the directionally selective light responses of starburst amacrine cells, interneurons that are pre-synaptic to ON-OFF directionally selective ganglion cells. PUBLIC HEALTH RELEVANCE: Increased knowledge of chloride cotransporter activity in the adult retina will aid in the understanding of human retinal function and dysfunction, as well as provide the basis for drug therapy for retinal disorders, such as retinal ischemia, that involve the chloride cotransporters. In addition, increased knowledge of chloride cotransporters may aid in the understanding and treatment of epilepsy and other diseases that involve chloride homeostasis and GABA.