GABA‐immunoreactive starburst amacrine cells in pigmented and albino rats

Abstract

In this study we tested whether the critical anatomical substrate for retinal direction selectivity is altered in albino mammals. We used dual immunostaining for GABA and choline acetyltransferase and quantitatively analyzed the number of double-labelled starburst amacrine cells in wild-type and albino rats. In albino rats, the percentage of ON-amacrine cells with high GABA content was significantly lower than in pigmented animals. OFF-amacrines did not significantly differ between the two rat strains. Thus, the decreased GABA content in ON-amacrine cells could reflect an altered neuronal substrate for retinal direction selectivity. These results are discussed in relation to the optokinetic deficits described in albino mammals.

Comparison of visual function in pigmented and albino rats by electroretinography and visual evoked potentials

“…ON-amacrine cells contribute to the generation of direction selectivity of ganglion cell response innervating the opto-kinetic system. Although the authors discuss that the difference found in GABA-rich ON-starburst amacrine cells may be too subtle to explain the drastic physiological alterations seen in albino rats, at least some of these alterations could be caused by the smaller number of amacrine cells [7]. Donatien et al [12] reported on a reduced ganglion cell density in albino rabbits.…”

“…Except for a slightly reduced number of ganglion cells, no obvious anatomical differences with respect to horizontal, amacrine or ganglion cells were found between albino and pigmented rats. Nevertheless, there are less GABA-rich ON-starburst amacrine cells in Wistar rats than in Long-Evans rats, which could be indicate differences in the retinal neuronal circuitry [7]. ON-amacrine cells contribute to the generation of direction selectivity of ganglion cell response innervating the opto-kinetic system.…”

Protein kinase C immunoreactivity in the pigmented and albino rat retina

“…Differences between pigmented and albino in the distribution of other retinal cell types have been identified in previous studies. Amacrine cell populations and the ganglion cell population have been shown to be disrupted in the albino phenotype in a variety of rodent and carnivore species (Stone et al ., 1978; Morgan et al ., 1987; Oyster et al ., 1987; Mitrofanis & Stone, 1988; Jeffery & Kinsella, 1992; Donatien et al ., 2002; Blaszczyk et al ., 2004). In contrast, the horizontal cell distribution appears normal in albino mouse (Raven & Reese, 2002).…”

“…Studies also suggest defects of specific cell populations in the albino retina. One amacrine cell subpopulation is increased in number in albino rats and Siamese cats (Mitrofanis & Stone, 1988) whereas another is significantly decreased in number in albino rats (Blaszczyk et al ., 2004). Estimates of ganglion cell numbers show a decrease in the Siamese cat, albino rabbit and albino ferret (Stone et al ., 1978; Morgan et al ., 1987; Oyster et al ., 1987; Jeffery & Kinsella, 1992; Donatien et al ., 2002).…”

“…The reduction in the thickness of the inner nuclear layer implies that one or more of the cellular components within that layer are altered in the albino. One of those components, the horizontal cell, has been shown to be normal in albino mice (Raven & Reese, 2002) and although one amacrine subpopulation has been found to be decreased (Blaszczyk et al ., 2004) another component has been shown to be increased in number in the albino (Mitrofanis & Stone, 1988). Is the decreased thickness of the inner nuclear layer in albinos therefore due to a decrease in a third component, the bipolar cell population?…”