Department of Optometry and Vision Science, University of Auckland, Private Bag 92019, Auckland, New Zealand.
Exp Eye Res. 2012 Jan;94(1):71-84. doi: 10.1016/j.exer.2011.11.008. Epub 2011 Nov 25.
Glutamate is the major neurotransmitter in the vertebrate retina. Neurons involved in the glutamate pathway express α-amino-3-hydroxyl-5-methylisoxazole-4-propionic acid (AMPA), kainic acid (KA) and N-methyl-D-aspartate (NMDA) receptors. Functional characterization of these ionotropic glutamate receptors can be achieved by using a cation channel permeating probe named agmatine (1-amino-4-guanidobutane; AGB). Retinal mapping using this guanidinium analog has certain advantages including the immunocytochemical identification of a whole population of neurons expressing functional glutamate gated receptor channels. We have extended AGB studies into the functionality of ionotropic receptors in peripheral aged human retina to serve as a comparison for functional analysis of retinopathies such as retinal detachment. We probed the human retina with AGB after activation with AMPA, KA and NMDA. The results showed patterns of AGB entry into neurons consistent with those previously observed in subunit localization studies in adult mammalian retinae including primates. Application of 30 μM AMPA activated receptors in virtually all calretinin immunoreactive AII amacrine cells in the mid-peripheral human retina. About half of the AII amacrine cells showed AGB permeation after incubation with 50 μM KA. Some bipolar cells including DB3 OFF bipolar cells displayed functional KA receptors. Colocalization of AGB with parvalbumin labeled horizontal cells revealed functional KA and AMPA receptors with no responsiveness to NMDA activation. NMDA activation resulted in AGB labeling of ganglion cells and amacrine cells. The present study provides a description of functional ionotropic glutamate receptors in the aged mid-peripheral human retina.
谷氨酸是脊椎动物视网膜中的主要神经递质。参与谷氨酸途径的神经元表达α-氨基-3-羟基-5-甲基异恶唑-4-丙酸（AMPA）、海人酸（KA）和 N-甲基-D-天冬氨酸（NMDA）受体。使用名为胍丁胺（1-氨基-4-胍丁烷；AGB）的阳离子通道渗透探针可以实现这些离子型谷氨酸受体的功能特征。使用这种胍基类似物进行视网膜映射具有某些优势，包括免疫细胞化学鉴定表达功能性谷氨酸门控受体通道的整个神经元群体。我们已经将 AGB 研究扩展到外周老年人类视网膜中离子型受体的功能，以作为视网膜脱离等视网膜病变的功能分析的比较。我们在用 AMPA、KA 和 NMDA 激活后用 AGB 探测人类视网膜。结果显示，AGB 进入神经元的模式与在成年哺乳动物视网膜亚基定位研究中观察到的模式一致，包括灵长类动物。在人类视网膜的中周边，应用 30μM 的 AMPA 激活了几乎所有的 calretinin 免疫反应性 AII 无长突细胞中的受体。在用 50μM KA 孵育后，约一半的 AII 无长突细胞表现出 AGB 渗透。包括 DB3 OFF 双极细胞在内的一些双极细胞显示出功能性 KA 受体。AGB 与标记水平细胞的 parvalbumin 共定位揭示了功能性 KA 和 AMPA 受体，对 NMDA 激活没有反应。NMDA 激活导致节细胞和无长突细胞的 AGB 标记。本研究提供了对老年人类中周边视网膜中功能性离子型谷氨酸受体的描述。
