Subcellular localization of neuronal nitric oxide synthase in turtle retina: electron immunocytochemistry

Vis Neurosci. 2001 Nov-Dec;18(6):949-60.

Abstract

Recent studies imaging nitric oxide (NO) production in the retina have indicated a much wider distribution of NO production than would be suggested by previous light-microscopic localizations of neuronal nitric oxide synthase (nNOS). To help resolve this discrepancy, the present study analyzed the ultrastructural localization of nNOS-like immunoreactivity (-LI) in all layers of the retina. In the ellipsoids of rod photoreceptors and the accessory elements of double cones, nNOS-LI was associated with some atypical mitochondria. In the outer plexiform layer, nNOS-LI was in some postsynaptic horizontal and bipolar cell processes at photoreceptor ribbon synapses. In some amacrine and ganglion cell somata, nNOS-LI was diffusely localized in the cytoplasm and associated with the endoplasmic reticulum. In the inner plexiform layer, nNOS-LI diffusely filled some amacrine cell processes, while in other amacrine cells nNOS-LI was selectively localized at the presynaptic specializations of conventional synapses. Neuronal NOS-LI was also found at membrane specializations in bipolar cell terminals that were distinct from their normal ribbon synapses. Finally, some nNOS-LI was found in mitochondria in Muller cells. The diverse subcellular localizations of nNOS-LI indicates that NO may play distinct functional roles in many retinal cells, which correlates well with the widespread NO production found in previous NO imaging studies.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Amacrine Cells / enzymology
  • Amacrine Cells / ultrastructure
  • Animals
  • Interneurons / enzymology
  • Interneurons / ultrastructure
  • Microscopy, Immunoelectron
  • Nitric Oxide Synthase / metabolism*
  • Nitric Oxide Synthase Type I
  • Photoreceptor Cells, Vertebrate / enzymology
  • Photoreceptor Cells, Vertebrate / ultrastructure
  • Retina / enzymology*
  • Retina / ultrastructure
  • Retinal Ganglion Cells / enzymology
  • Retinal Ganglion Cells / ultrastructure
  • Subcellular Fractions / enzymology
  • Subcellular Fractions / ultrastructure
  • Synapses / enzymology
  • Synapses / ultrastructure
  • Turtles

Substances

  • Nitric Oxide Synthase
  • Nitric Oxide Synthase Type I