Subcellular localization of neuronal nitric oxide synthase in turtle retina: electron immunocytochemistry.
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.
Cao
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Department of Biology, Boston University, Massachusetts 02215, USA.
Eldred
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D025042:Amacrine Cells / Q000201:enzymology / Q000648:ultrastructure; D000818:Animals; D007395:Interneurons / Q000201:enzymology / Q000648:ultrastructure; D016253:Microscopy, Immunoelectron; D019001:Nitric Oxide Synthase / Q000378:metabolism*; D052248:Nitric Oxide Synthase Type I; D020419:Photoreceptor Cells, Vertebrate / Q000201:enzymology / Q000648:ultrastructure; D012160:Retina / Q000201:enzymology* / Q000648:ultrastructure; D012165:Retinal Ganglion Cells / Q000201:enzymology / Q000648:ultrastructure; D013347:Subcellular Fractions / Q000201:enzymology / Q000648:ultrastructure; D013569:Synapses / Q000201:enzymology / Q000648:ultrastructure; D014426:Turtles
D019001:Nitric Oxide Synthase; D052248:Nitric Oxide Synthase Type I