Purchase this article with an account.
S. Chung, A. Picones, J.I. Korenbrot; Developmental Maturation of Passive Electrical Properties of Retinal Ganglion Cells . Invest. Ophthalmol. Vis. Sci. 2003;44(13):1656.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
Purpose: To assess the information processing features of maturing RGC, we measured the passive electrotonic properties of RGC in the peripheral growth zone (PGZ) of trout retina. In the PGZ, RGC at all developrmental stages are present, side-by-side, and can be studied both anatomically and electrophysiologically. Methods: The entire dendritic arbor of individual RGC in retinal flat mounts that include the PGZ, was labeled with fluorescent, membrane bound dyes (diI and diO) delivered by the diOlistic technique. The morphometric features of the dendritc tree were characterized through computer-assisted analysis (NeuroLucida) of 2-dimesnional plane projections of the arbor. The passive electrical properties of individual RGC were characterized by analysis of the charging currents measured in response to small voltage-steps in voltage-clamped RGC. RGC were voltage-clamped using tight-seal electrodes in retinal slices that included the PGZ. Results and Conclusions: RGC develop throug three histologically distinct zones in the PGZ: bulge, transition and mature. In the most peripheral ¾ of the bulge zone, cells have rounded somas, lack dendritic extensions and some are coupled so that membrane bound dyes traverse from one cell to its immediate neighbors. In the more central ¼ of the bulge, cell’s dendrites are few, short and of limited branching. In the transition zone dendritic arbors becomes progressively more expansive and branched. Regardless of the size and branching pattern of the developing RGC dendritic arbor, the ratio of the diameters of parent and progeny dendrites at any branching nodes is well described by Rall’s 3/2-power law. Given this anatomical feature, the RGC passive electrical properties are well described by an equivalent electrical circuit consisting of an isopotential cell body in parallel with a single equivalent cylinder of finite length. As RGC develop the electrical properties of their dendritic arbor change in an orderly and tightly regulated manner, not randomly. Electrically, dendritic arbors develop along either of two distinct modes, but only these modes: isoelectrotonic and isometric. In isoelectrotonic growth, electrotonic properties are constant regardless of the absolute dimensions of the dendritic arbor or its branching geometry. These cells maintain unvarying relative synaptic efficacy independently of the size or pattern of their dendritic arbor. In isometric growth, in contrast, electronic properties change, but the ratio of the changing electrotonic length to electrotonic diameter is constant. In these cells relative synaptic efficacy decreases linearly as dendrites extend.
This PDF is available to Subscribers Only