Puthussery Theresa, Fletcher Erica L
Department of Anatomy and Cell Biology, The University of Melbourne, Parkville, Victoria, Australia.
J Comp Neurol. 2006 Jun 10;496(5):595-609. doi: 10.1002/cne.20889.
Extracellular ATP is known to mediate fast, excitatory neurotransmission through activation of ionotropic P2X receptors. In this study, the localization of the P2X(2) receptor (P2X(2)R) subunit was studied in rat retina by using immunofluorescence immunohistochemistry and preembedding immunoelectron microscopy. The P2X(2)R was observed in large ganglion cells as well as in a subset of amacrine cells. Double labeling revealed that 96% of all P2X(2)R-immunoreactive amacrine cells showed gamma-aminobutyric acid (GABA) immunoreactivity. Subsets of P2X(2)R-immunoreactive amacrine cells expressed nitric oxide synthase and substance P; however, no colocalization was observed with choline acetyltransferase, vasoactive intestinal peptide, or tyrosine hydroxylase. Nearest-neighbor analysis confirmed that P2X(2)Rs were expressed by a heterogeneous population of amacrine cells. The synaptic connectivity of P2X(2)R amacrine cells was also investigated. It was interesting that P2X(2)R-immunoreactive amacrine cell dendrites stratified in the sublaminae of the inner plexiform layer occupied by cone, but not rod bipolar cell axon terminals. Immunoelectron microscopy revealed that P2X(2)-immunoreactive amacrine cell processes were associated with cone bipolar cell axon terminals as well as other conventional synapses in the inner plexiform layer. Taken together, these data provide further evidence for the involvement of extracellular ATP in neuronal signaling in the retina, particularly within cone pathways.
已知细胞外ATP通过激活离子型P2X受体介导快速兴奋性神经传递。在本研究中，利用免疫荧光免疫组织化学和包埋前免疫电子显微镜技术研究了大鼠视网膜中P2X(2)受体（P2X(2)R）亚基的定位。在大神经节细胞以及一部分无长突细胞中观察到了P2X(2)R。双重标记显示，所有P2X(2)R免疫反应性无长突细胞中有96%显示γ-氨基丁酸（GABA）免疫反应性。P2X(2)R免疫反应性无长突细胞亚群表达一氧化氮合酶和P物质；然而，未观察到与胆碱乙酰转移酶、血管活性肠肽或酪氨酸羟化酶的共定位。最近邻分析证实P2X(2)Rs由异质性的无长突细胞群体表达。还研究了P2X(2)R无长突细胞的突触连接性。有趣的是，P2X(2)R免疫反应性无长突细胞的树突分层在内网状层由视锥细胞而非视杆双极细胞轴突终末占据的亚层中。免疫电子显微镜显示，P2X(2)免疫反应性无长突细胞的突起与视锥双极细胞轴突终末以及内网状层中的其他传统突触相关。综上所述，这些数据为细胞外ATP参与视网膜神经元信号传导，特别是在视锥细胞通路中的作用提供了进一步证据。
