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Synaptic localization of P2X 7 receptors in the rat retina
Author(s) -
Puthussery Theresa,
Fletcher Erica L.
Publication year - 2004
Publication title -
journal of comparative neurology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.855
H-Index - 209
eISSN - 1096-9861
pISSN - 0021-9967
DOI - 10.1002/cne.20045
Subject(s) - colocalization , biology , outer plexiform layer , inner plexiform layer , immunoelectron microscopy , retina , microbiology and biotechnology , photoreceptor cell , synapse , calbindin , ribbon synapse , neurotransmission , neuroscience , receptor , synaptic vesicle , biochemistry , vesicle , immunohistochemistry , membrane , immunology
Abstract The distribution of P2X 7 receptor (P2X 7 R) subunits was studied in the rat retina using a subunit‐specific antiserum. Punctate immunofluorescence was observed in the inner and outer plexiform layers. Double labeling of P2X 7 and the horizontal cell marker, calbindin, revealed extensive colocalization in the outer plexiform layer (OPL). Significant colocalization of P2X 7 R and kinesin, a marker of photoreceptor ribbons, was also observed, indicating that this receptor may be expressed at photoreceptor terminals. Furthermore, another band of P2X 7 R puncta was identified below the level of the photoreceptor terminals, adjacent to the inner nuclear layer (INL). This band of P2X 7 R puncta colocalized with the active‐zone protein, bassoon, suggesting that “synapse‐like” structures exist outside photoreceptor terminals. Preembedding immunoelectron microscopy demonstrated P2X 7 R labeling of photoreceptor terminals adjacent to ribbons. In addition, some horizontal cell dendrites and putative “desmosome‐like” junctions below cone pedicles were labeled. In the inner plexiform layer (IPL), P2X 7 R puncta were observed surrounding terminals immunoreactive for protein kinase C‐α, a marker of rod bipolar cells. Double labeling with bassoon in the IPL revealed extensive colocalization, indicating that P2X 7 R is likely to be found at conventional cell synapses. This finding was confirmed at the ultrastructural level: only processes presynaptic to rod bipolar cells were found to be labeled for the P2X 7 R, as well as other conventional synapses. These findings suggest that purines play a significant role in neurotransmission within the retina, and may modulate both photoreceptor and rod bipolar cell responses. J. Comp. Neurol. 472:13–23, 2004. © 2004 Wiley‐Liss, Inc.