Olson A J, Picones A, Korenbrot J I
Department of Physiology, School of Medicine, University of California at San Francisco, San Francisco, California 94143, USA.
J Neurophysiol. 2000 Oct;84(4):2063-77. doi: 10.1152/jn.2000.84.4.2063.
In the retina of teleost fish, continuous neuronal development occurs at the margin, in the peripheral growth zone (PGZ). We prepared tissue slices from the retina of rainbow trout that include the PGZ and that comprise a time line of retinal development, in which cells at progressive stages of differentiation are present side by side. We studied the changes in dendritic structure and voltage-dependent Ca(2+), Na(+), and K(+) currents that occur as ganglion cells mature. The youngest ganglion cells form a distinct bulge. Cells in the bulge have spare and short dendritic trees. Only half express Ca(2+) currents and then only high-voltage-activated currents with slow inactivation (HVAslow). Bulge cells are rarely electrically excitable. They express a mixture of rapidly inactivating and noninactivating K(+) currents (IKA and IKdr). The ganglion cells next organize into a transition zone, consisting of a layered structure two to three nuclei thick, before forming the single layered structure characteristic of the mature retina. In the transition zone, the dendritic arbor is elaborately branched and extends over multiple laminae in the inner plexiform layer, without apparent stratification. The arbor of the mature cells is stratified, and the span of the dendritic arbor is well over five times the cell body's diameter. The electrical properties of cells in the transition and mature zones differ significantly from those in the bulge cells. Correlated with the more elaborate dendritic structures are the expression of both rapidly inactivating HVA (HVAfast) and of low-voltage-activated (LVA) Ca(2+) currents and of a high density of Na(+) currents that renders the cells electrically excitable. The older ganglion cells also express a slowly activating K(+) current (IKsa).
在硬骨鱼的视网膜中，连续的神经元发育发生在边缘的外周生长区（PGZ）。我们从虹鳟鱼的视网膜制备了包含PGZ且构成视网膜发育时间线的组织切片，其中处于不同分化阶段的细胞并排存在。我们研究了随着神经节细胞成熟，其树突结构以及电压依赖性钙（Ca²⁺）、钠（Na⁺）和钾（K⁺）电流的变化。最年轻的神经节细胞形成一个明显的凸起。凸起中的细胞具有稀疏且短的树突树。只有一半细胞表达Ca²⁺电流，且仅表达具有缓慢失活的高电压激活电流（HVA慢）。凸起细胞很少能产生电兴奋。它们表达快速失活和非失活钾电流的混合物（IKA和IKdr）。接下来，神经节细胞组织成一个过渡区，该过渡区由两到三个核厚的分层结构组成，然后才形成成熟视网膜特有的单层结构。在过渡区，树突分支精细，在内网状层的多个板层上延伸，没有明显的分层。成熟细胞的树突是分层的，树突分支的跨度远超过细胞体直径的五倍。过渡区和成熟区细胞的电特性与凸起细胞的电特性有显著差异。与更精细的树突结构相关的是快速失活的高电压激活电流（HVA快）、低电压激活（LVA）钙电流以及高密度钠电流的表达，这些使细胞具有电兴奋性。较老的神经节细胞还表达一种缓慢激活的钾电流（IKsa）。
