Morphology of catecholamine-containing amacrine cells in the cat's retina, as seen in retinal whole mounts.

The morphology of catecholaminergic cells of the cat's retina was studied by fluorescence microscopy of retinal whole mounts. Although varied in soma shape, these cells seem to represent a single group of cells with an average soma diameter of 14.5 micrometer in freeze-dried material. The fluorescent terminals of these cells formed a striking two-dimensional pattern: a significant portion of them appeared to be arranged in rings located at the boundary of the inner plexiform and inner nuclear layers. The mean diameter of these rings was 9.7 micrometer and their pattern appeared to extend unbroken across the retina. It was, in general, not possible to observe the connection between these rings and fluorescent somas, except when a ring was in a juxtasomatic position. It is suggested that the postsynaptic somas within these rings are either of other amacrines or of interplexiform cells. Using the Golgi-Colonnier technique on retinal whole mounts, an attempt was made to identify the cell type which resembles the catecholaminergic cell in its size, location and morphology. The suggested cell type appears to be among the largest amacrine cells, (mean soma size of 11.5 micrometer in Golgi material) with a considerable dendritic network at the border of the inner plexiform and inner nuclear layers, although there are branches reaching as far as the middle of the inner plexiform layer.