Distribution and spatial geometry of dopamine interplexiform cells in the rat retina: I. Developing retina

Abstract

The morphology and distribution of dopaminergic interplexiform cells were analyzed in 9-day-old rat retinas processed as wholemounts for tyrosine hydroxylase immunohistochemistry. The mean number of dopaminergic interplexiform cells was estimated as about half of the total number of dopaminergic neurons in the immature retina, with a higher density in the temporal retina. Four interplexiform cells were individually analyzed and reconstructed with a computer system. Their arborizations could be divided into three different regions based on both their morphological features and their position within the retinal layers: (1) an internal arborization, spreading at the margin between the inner nuclear layer and the inner plexiform layer, composed of long, thick, somatofugal dendrites branching at acute angles, (2) an external arborization in the middle of the inner nuclear layer, formed by short, thin, varicose, recurved, axon-like processes branching at right angles, (3) and one or more scleral process(es), originating either from the cell body or from the internal arborization, running toward the outermost cell row of the INL, some of which reached the outer plexiform layer. Finally, analysis of the arborization network by computer simulations based on the 4 digitalized cells was compared with a nearest-neighbour analysis of cell body distribution. It showed that cell bodies are almost randomly distributed--at least in the inferior retina--but that an adjustment of dendritic growth and orientation probably occurs to ensure a homogeneous coverage of the retina with a constant degree of overlap in the adult. This report represents the first three-dimensional computer reconstruction of chemically identified neurons in the retina.

Development of morphological types and distribution patterns of amacrine cells immunoreactive to tyrosine hydroxylase in the cat retina

“…The postnatal morphological development of dopaminergic neurons has been studied in rat (Nguyen-Legros et al, 1983;Savy et al, 1989), guinea pig (Parkinson et al, 1985), mouse (Wulle & Schnitzer, 1989), and rabbit (Lam et al, 1981). The developmental history in these mammalian species is closely similar to what we have observed in the kitten.…”

Determinants of the exclusion zone in dopaminergic amacrine cell mosaics

“…Perhaps the most unusual feature of these cells, relative to other cell types, is that they give rise to extremely widefield dendritic arbors and extensive axonal processes that together blanket the retina within the outermost stratum, S 1 , of the IPL (Kolb et al, 1981;Versaux-Botteri et al, 1984;Oyster et al, 1985;Savy et al, 1989;Wulle and Schnitzer, 1989;Dacey, 1990;Mü ller and Peichl, 1991). Indeed, their dendritic arbors, often asymmetrically distributed around the cell, may be oriented to compensate for the irregular distribution of their somata to ensure local uniform coverage by their pro- Figure 2c is due to small sample sizes (see Cook, 1996).…”

Photomechanical movements of cultured embryonic photoreceptors: regulation by exogenous neuromodulators and by a regulable source of endogenous dopamine

“…Dopamine synthesis and release has been documented in the retinae of several species (Kramer, 197 1;Iuvone et al, 1978). The dopamine synthetic enzyme TH has been localized to subtypes of amacrine cells (Brecha et al, 1984) and/or to interplexiform cells (Savy et al, 1989). In developing chick retina, TH-immunoreactive cells are first seen on El 1, are initially morphologically undifferentiated (Araki et al, 1982;Kagami et al, 199 l), and assume their adult positions and morphology by E20.…”