Abstract
Abstract: :
Purpose: We examined the distribution and types of ganglion cells in the zebrafish retina, a model vertebrate genetic organism. Methods: Ganglion cell layer neurons were stained with cresyl violet and methylene blue. The dendrites of individual zebrafish ganglion cells were labeled by backfilling with DiI through the optic nerve followed by reconstruction using confocal microscopy. The stratification and branching pattern of each ganglion cell was examined in relation to the borders of the inner plexiform layer (IPL). Results: An "area centralis" was found in the ventral-temporal region of the zebrafish retina. The density of neurons averaged from ∼12,000/mm2 in the dorsal-nasal retina to a peak of ∼37,000/mm2 in the ventral-temporal retina. By dye backfilling, we identified 11 different ganglion cell types. Two commonly labeled ganglion cells (OFF-Type III, ON-type VI) displayed highly stratified dendritic arborizations in the IPL. Their dendrites branched asymmetrically with many thorn-like varicosities, and profusely filled the area of arborization. Type V cells had dendrites that formed a small simply branching dendritic field in the ON-sublamina of the IPL, while types VII and VIII branched diffusely. Two large ganglion cell types (ON-Type I and OFF-type II) displayed widely branching dendritic fields in the IPL. Three different types of bistratified ganglion cells were found (Types, IX, X, and XI.) whose dendrites occupied different regions of the IPL. A distinctive feature of type XI cells was that their tertiary dendrites formed a series of vertical claw-like arbors. Conclusion: We conclude that zebrafish ganglion cells display a rich variety of types and branching patterns. This study establishes a series of baseline measurements of zebrafish ganglion cells to facilitate examination of genes playing a role in the specification and stratification of ganglion cell types. Support: EY00824 (J.E.D.) and the Zeigler Foundation (E.D.C.).
Keywords: 557 retina: proximal(bipolar, amacrine, and ganglion cells) • 559 retinal connections, networks, circuitry • 564 retinal development