Localization of the presynaptic cytomatrix protein Piccolo at ribbon and conventional synapses in the rat retina: comparison with Bassoon

J Comp Neurol. 2001 Oct 15;439(2):224-34. doi: 10.1002/cne.1344.


In recent years significant progress has been made in the elucidation of the molecular assembly of the postsynaptic density at synapses, whereas little is known as yet about the components of the presynaptic active zone. Piccolo and Bassoon, two structurally related presynaptic cytomatrix proteins, are highly concentrated at the active zones of both excitatory and inhibitory synapses in rat brain. In this study we used immunocytochemistry to examine the cellular and ultrastructural localization of Piccolo at synapses in the rat retina and compared it with that of Bassoon. Both proteins showed strong punctate immunofluorescence in the outer and the inner plexiform layers of the retina. They were found presynaptically at glutamatergic ribbon synapses and at conventional GABAergic and glycinergic synapses. Although the two proteins were coexpressed at all photoreceptor ribbon synapses and at some conventional amacrine cell synapses, at bipolar cell ribbon synapses only Piccolo was present. Our data demonstrate similarities but also differences in the molecular composition of the presynaptic apparatuses of the synapses in the retina, differences that may account for the functional differences observed between the ribbon and the conventional amacrine cell synapses and between the photoreceptor and the bipolar cell ribbon synapses in the retina.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Antibody Specificity / immunology
  • Cytoskeletal Proteins / metabolism*
  • Cytoskeleton / metabolism*
  • Cytoskeleton / ultrastructure
  • Fluorescent Antibody Technique
  • Glycine / metabolism
  • Microscopy, Confocal
  • Microscopy, Electron
  • Nerve Tissue Proteins / metabolism*
  • Neural Inhibition / physiology
  • Neuropeptides / metabolism*
  • Presynaptic Terminals / metabolism*
  • Presynaptic Terminals / ultrastructure*
  • Rats
  • Rats, Wistar / anatomy & histology
  • Rats, Wistar / metabolism*
  • Receptors, GABA-A / metabolism
  • Receptors, Glycine / metabolism
  • Retina / metabolism*
  • Retina / ultrastructure*
  • Retinal Cone Photoreceptor Cells / metabolism
  • Retinal Cone Photoreceptor Cells / ultrastructure
  • Retinal Rod Photoreceptor Cells / metabolism
  • Retinal Rod Photoreceptor Cells / ultrastructure
  • Synaptic Transmission / physiology
  • Vision, Ocular / physiology
  • gamma-Aminobutyric Acid / metabolism


  • Bsn protein, rat
  • Cytoskeletal Proteins
  • Nerve Tissue Proteins
  • Neuropeptides
  • Pclo protein, rat
  • Receptors, GABA-A
  • Receptors, Glycine
  • gamma-Aminobutyric Acid
  • Glycine