P2X2 receptors on ganglion and amacrine cells in cone pathways of the rat retina

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amacrine Cells / metabolism*
  • Amacrine Cells / ultrastructure
  • Animals
  • Immunohistochemistry
  • Microscopy, Immunoelectron
  • Presynaptic Terminals / metabolism
  • Rats
  • Rats, Sprague-Dawley
  • Receptors, Purinergic P2 / biosynthesis*
  • Receptors, Purinergic P2 / ultrastructure
  • Receptors, Purinergic P2X2
  • Retinal Cone Photoreceptor Cells / metabolism*
  • Retinal Cone Photoreceptor Cells / ultrastructure
  • Retinal Ganglion Cells / metabolism*
  • Retinal Ganglion Cells / ultrastructure
  • Retinal Rod Photoreceptor Cells / metabolism
  • Retinal Rod Photoreceptor Cells / ultrastructure
  • Synapses / metabolism
  • Synaptic Transmission
  • gamma-Aminobutyric Acid / metabolism


  • P2rx2 protein, rat
  • Receptors, Purinergic P2
  • Receptors, Purinergic P2X2
  • gamma-Aminobutyric Acid