title: Morphology and immunoreactivity of retrogradely double-labeled ganglion cells in the mouse retina.
abstract: OBJECTIVE
  To examine the specificity and reliability of a retrograde double-labeling technique that was recently established for identification of retinal ganglion cells (GCs) and to characterize the morphology of displaced (d)GCs (dGs).
  
  
  METHODS
  A mixture of the gap-junction-impermeable dye Lucifer yellow (LY) and the permeable dye neurobiotin (NB) was applied to the optic nerve stump for retrograde labeling of GCs and the cells coupled with them. A confocal microscope was adopted for morphologic observation.
  
  
  RESULTS
  GCs were identified by LY labeling, and they were all clearly labeled by NB. Cells coupled to GCs contained a weak NB signal but no LY. LY and NB revealed axon bundles, somas and dendrites of GCs. The retrogradely identified GCs numbered approximately 50,000 per retina, and they constituted 44% of the total neurons in the ganglion cell layer (GCL). Somas of retrogradely identified dGs were usually negative for glycine, ChAT (choline acetyltransferase), bNOS (brain-type nitric oxidase), GAD (glutamate decarboxylase), and glial markers, and occasionally, they were weakly GABA-positive. dGs averaged 760 per retina and composed 1.7% of total GCs. Sixteen morphologic subtypes of dGs were encountered, three of which were distinct from known GCs. dGs sent dendrites to either sublaminas of the IPL, mostly sublamina a.
  
  
  CONCLUSIONS
  The retrograde labeling is reliable for identification of GCs. dGs participate in ON and OFF light pathways but favor the OFF pathway. ChAT, bNOS, glycine, and GAD remain reliable AC markers in the GCL. GCs may couple to GABAergic ACs, and the gap junctions likely pass NB and GABA.
authors.affiliation: Department of Ophthalmology, Baylor College of Medicine, Houston, Texas 77030, USA. jpang@bcm.tmc.edu
authors.forename: Ji-Jie
authors.initials: JJ
authors.lastname: Pang
authors.forename: Samuel M
authors.initials: SM
authors.lastname: Wu
mesh_terms: D000818:Animals; D001710:Biotin / Q000031:analogs & derivatives*; D005260:Female; D007111:Immunity, Cellular; D007150:Immunohistochemistry; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D009900:Optic Nerve / Q000166:cytology / Q000276:immunology; D015203:Reproducibility of Results; D012165:Retinal Ganglion Cells / Q000166:cytology* / Q000276:immunology; D013194:Staining and Labeling / Q000379:methods*
chemical_list: C070614:neurobiotin; D001710:Biotin