Synaptic Localization of P2X7 Receptors in the Rat Retina

Theresa Puthussery, Erica L. Fletcher

Research output: Contribution to journalArticle

73 Scopus citations

Abstract

The distribution of P2X7 receptor (P2X7R) 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 P2X7 and the horizontal cell marker, calbindin, revealed extensive colocalization in the outer plexiform layer (OPL). Significant colocalization of P2X7R and kinesin, a marker of photoreceptor ribbons, was also observed, indicating that this receptor may be expressed at photoreceptor terminals. Furthermore, another band of P2X7R puncta was identified below the level of the photoreceptor terminals, adjacent to the inner nuclear layer (INL). This band of P2X7R puncta colocalized with the active-zone protein, bassoon, suggesting that "synapse-like" structures exist outside photoreceptor terminals. Preembedding immunoelectron microscopy demonstrated P2X7R labeling of photo-receptor 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), P2X7R 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 P2X7R 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 P2X7R, 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.

Original languageEnglish (US)
Pages (from-to)13-23
Number of pages11
JournalJournal of Comparative Neurology
Volume472
Issue number1
DOIs
StatePublished - Apr 19 2004

Keywords

  • Photoreceptor
  • Postsynaptic
  • Purine
  • Purinergic receptor
  • Retina
  • Rod bipolar cell

ASJC Scopus subject areas

  • Neuroscience(all)

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