Horizontal cells in the retina of a diurnal rodent, the agouti (Dasyprocta aguti)

Abstract

The morphology and distribution of normally placed and displaced A horizontal cells were studied in the retina of a diurnal hystricomorph rodent, the agouti Dasyprocta aguti. Cells were labeled with anti-calbindin immunocytochemistry. Dendritic-field size reaches a minimum in the visual streak, of about 9,000 microm(2), and increases toward the retinal periphery both in the dorsal and ventral regions. There is a dorsoventral asymmetry, with dorsal cells being larger than ventral cells at equal distances from the streak. The peak value for cell density of 281 +/- 28 cells/mm(2) occurs in the center of the visual streak, decreasing toward the dorsal and ventral retinal periphery, paralleling the increase in dendritic-field size. Along the visual streak, the decline in cell density is less pronounced, remaining between 100-200 cells/mm(2) in the temporal and nasal periphery. Displaced horizontal cells are rare and occur in the retinal periphery. They tend to be smaller than normally placed horizontal cells in the ventral region, whilst no systematic difference was observed between the two cell groups in the dorsal region. Mosaic regularity was studied using nearest-neighbor analysis and the Ripley function. When mosaic regularity was determined removing the displaced horizontal cells, there was a slight increase in the conformity ratio, but the bivariate Ripley function indicated some repulsive dependence between the two mosaics. Both results were near the level of significance. A similar analysis performed in the capybara retina, a closely related hystricomorph rodent bearing a higher density of displaced horizontal cells than found in the agouti, suggested spatial independence between the two mosaics, normally placed versus displaced horizontal cells.

Ganglion Cell and Displaced Amacrine Cell Density Distribution in the Retina of the Howler Monkey (Alouatta caraya)

“…Other neurons of the retinal ganglion cell layer comprised displaced amacrine cells and displaced horizontal cells, the later relatively rare in comparison with the former [42] – [44] . Displaced amacrine cells had small cell bodies, dark staining nuclei, rarely visible nucleoli, and scant cytoplasm.…”

“…Ganglion cells comprise a heterogeneous population of neurons readily distinguishable from other neurons (thin arrows), glial cells (thick arrows), and endothelial cells. The non-ganglion cell neurons of the retinal ganglion cell layer comprise displaced amacrine cells and displaced horizontal cells, the later relatively rare in comparison with the former [42] – [44] . The glial cells comprise microglia (thick arrow in B ) and astrocytes (thick arrow in D ), which are generally located internally (microglia) or externally (astrocytes and microglia) to the retinal ganglion cells.…”

The topography of cone photoreceptors in the retina of a diurnal rodent, the agouti (Dasyprocta aguti)

“…Silveira et al (1989) evaluated the distribution of retinal ganglion cells and found a well-developed visual streak, a nasotemporal band of high ganglion cell density located about 2–3 mm dorsal to the optic disk, and a dorsoventral asymmetry in ganglion cell topography. A recent paper described the retinal topography of A-type horizontal cells using immunocytochemistry (de Lima et al, 2005). Interestingly, the density of this cell type that exclusively connects to cones also showed a dorsoventral asymmetry with respect to dendritic field size.…”

“…In the present work, we used immunocytochemistry with cone opsin–specific antibodies to study the retinal topography and mosaic regularity of cone photoreceptors of the agouti ( Dasyprocta aguti ), a hystricomorph rodent of large body size displaying a predominantly diurnal, visually guided behavior. The agouti’s visual system has been the subject of several studies concerning eye optics (Oswaldo-Cruz et al, 1985), horizontal cell morphology and density (de Lima et al, 2005), ganglion cell morphology and density (Silveira et al, 1989; Gomes et al, 1998), and visual cortex morphology and physiology (Picanço-Diniz et al, 1989, 1991, 1992; Costa et al, 1996; Elston et al, 2006). Part of the present results have previously been presented in abstract form (de Lima et al, 2001).…”

Spatial constraints underlying the retinal mosaics of two types of horizontal cells in cat and macaque

“…Data sets Three horizontal cell fields were analysed: fields A and B are from macaque (A: unpublished data; B: Figure 7 of Wässle et al (2000)); field C is from cat ( Figure 12 of ). To keep our notation concise (rather than claiming any equivalence of neuronal types across species), we denote type B cat horizontal cells as "type 1", and type A horizontal cells as "type 2", in line with previously-noted similarities of primate H1 and other mammalian B cells (de Lima et al, 2005). Fields were digitised, and the cell location taken to be the centre of each soma.…”