title: Immunolocalization of the P2X4 receptor on neurons and glia in the mammalian retina.
abstract: Extracellular adenosine 5'-triphosphate (eATP) acts as a neurotransmitter within the retina and brain, activating a range of ionotropic P2X and metabotropic P2Y receptors. In this study, the specific localization of the P2X4 receptor (P2X4-R) subunit was evaluated in the retina using fluorescence immunohistochemistry and pre-embedding immuno-electron microscopy. Punctate P2X4-R labeling was largely localized to the inner and outer plexiform layers of mouse, rat and cat retinae. In the mouse outer retina, double-labeling of P2X4-R with the horizontal cell marker, calbindin, revealed P2X4-R immunoreactivity (P2X4-R-IR) on horizontal cell somata and processes. In the inner retina, P2X4-R expression was found closely associated with rod and cone bipolar cell terminals, and the punctate labeling was observed on calretinin-positive amacrine cells. Using immuno-electron microscopy, P2X4-Rs were observed on processes post-synaptic to photoreceptor and bipolar cell terminals, likely representing horizontal, amacrine and ganglion cells, respectively. Furthermore, P2X4-R expression was also observed on Müller cells, astrocytes and microglia. These data suggest a role for P2X4-Rs in the lateral inhibitory pathways of the retina, modulating neuronal function of photoreceptors and bipolar cells. The expression on macro- and microglial cells implicates a role for P2X4-Rs in glial signaling, tissue homeostasis and immunosurveillance within the mammalian retina.
authors.affiliation: Department of Anatomy and Neuroscience, The University of Melbourne, Melbourne, Victoria, Australia.
authors.forename: T
authors.initials: T
authors.lastname: Ho
authors.affiliation: Department of Anatomy and Neuroscience, The University of Melbourne, Melbourne, Victoria, Australia.
authors.forename: K A
authors.initials: KA
authors.lastname: Vessey
authors.affiliation: Department of Anatomy and Neuroscience, The University of Melbourne, Melbourne, Victoria, Australia. Electronic address: elf@unimelb.edu.au.
authors.forename: E L
authors.initials: EL
authors.lastname: Fletcher
mesh_terms: D000818:Animals; D015153:Blotting, Western; D002415:Cats; D005455:Fluorescent Antibody Technique; D021621:Imaging, Three-Dimensional; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D018613:Microscopy, Confocal; D016253:Microscopy, Immunoelectron; D009457:Neuroglia / Q000378:metabolism* / Q000648:ultrastructure; D009474:Neurons / Q000378:metabolism* / Q000648:ultrastructure; D010784:Photomicrography; D051381:Rats; D058848:Receptors, Purinergic P2X4 / Q000378:metabolism*; D012160:Retina / Q000378:metabolism* / Q000648:ultrastructure; D013045:Species Specificity
chemical_list: D058848:Receptors, Purinergic P2X4
keywords: Müller cell; extracellular ATP; microglia; purinergic; retinal neurons; synapse