Analysis of dendritic arbors of native and regenerated ganglion cells in the goldfish retina

Abstract

The retinas of adult teleost fish can regenerate following injury, but little is known about the neuronal integration of the visual scene that is performed by the regenerated retina. Using goldfish retinal ganglion cells (RGCs) as the experimental system, an evaluation of dendritic arbor structure and passive electrotonic properties was developed, the aim being to quantitatively test the hypothesis that native and regenerated RGC dendritic arbors have similar structural and modeled electrotonic attributes. Fractal dimension was chosen as the descriptor of RGC dendritic arbor complexity, and the arbors' transfer function magnitudes were estimated using an electrically passive, equivalent-circuit analysis. For both native and regenerated RGCs, arbors qualitatively judged to be simple tended to have lower fractal dimension values than arbors judged to be more complex. All cells had similar cut-off frequencies, and for random stimulation of greater than 25% of an RGC's population of dendritic tips, there was a positive correlation between fractal dimension and transfer function magnitude. Some regenerated RGCs had abnormally long primary dendrites, but neither the distributions of fractal dimension values, nor the estimated transfer function magnitudes, were significantly different between native and regenerated RGCs. The results appear to support the hypothesis that structural and modeled electrotonic attributes of regenerated goldfish RGCs are similar to those of native RGCs, suggesting that regenerated RGCs may restore normal visual function.